spring <context:annotation-config> 跟 <context:component-scan>诠释及区别

最新推荐文章于 2021-10-17 02:34:45 发布

转载最新推荐文章于 2021-10-17 02:34:45 发布 · 1k 阅读

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本文详细解释了Spring框架中context:annotation-config与context:component-scan的区别，包括它们的功能、作用方式及在实际应用中的使用场景。通过实例分析，展示了它们如何在bean注册、依赖注入等方面发挥各自的作用。

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<context:annotation-config> 和 <context:component-scan>的区别

Difference between <context:annotation-config> vs <context:component-scan>

<context:annotation-config> 是用于激活那些已经在spring容器里注册过的bean（无论是通过xml的方式还是通过package sanning的方式）上面的注解，是一个注解处理工具。

<context:component-scan>除了具有<context:annotation-config>的功能之外，<context:component-scan>还可以在指定的package下扫描以及注册javabean 。

下面我们通过例子来详细查看他们的区别，

有三个class A,B,C,并且B,C的对象被注入到A中.

[java]view plaincopy 
    
 package com.xxx;  
 public class B {  
   public B() {  
     System.out.println("creating bean B: " + this);  
   }  
 }  
   
 package com.xxx;  
 public class C {  
   public C() {  
     System.out.println("creating bean C: " + this);  
   }  
 }  
   
 package com.yyy;  
 import com.xxx.B;  
 import com.xxx.C;  
 public class A {   
   private B bbb;  
   private C ccc;  
   public A() {  
     System.out.println("creating bean A: " + this);  
   }  
   public void setBbb(B bbb) {  
     System.out.println("setting A.bbb with " + bbb);  
     this.bbb = bbb;  
   }  
   public void setCcc(C ccc) {  
     System.out.println("setting A.ccc with " + ccc);  
     this.ccc = ccc;   
   }  
 }  

在applicationContext.xml中加入下面的配置 :

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx.B"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">
<</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"cBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx.C"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>
</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"aBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.yyy.A"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">
  <</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">property name</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bbb"</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> ref</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bBean"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>
  </span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">property name</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"ccc"</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> ref</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"cBean"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">
</</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">></span></code>

加载applicationContext.xml配置文件，将得到下面的结果:

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@c2ff5
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@1e8a1f6
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@1e152c5
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bbb with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@c2ff5
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">ccc with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@1e8a1f6</span></code>

OK, 这个结果没什么好说的，就是完全通过xml的方式，不过太过时了，下面通过注解的方式来简化我们的xml配置文件

首先，我们使用autowire的方式将对象bbb和ccc注入到A中：

[java]view plaincopy 
    
 package com.yyy;  
 import org.springframework.beans.factory.annotation.Autowired;  
 import com.xxx.B;  
 import com.xxx.C;  
 public class A {   
   private B bbb;  
   private C ccc;  
   public A() {  
     System.out.println("creating bean A: " + this);  
   }  
   @Autowired  
   public void setBbb(B bbb) {  
     System.out.println("setting A.bbb with " + bbb);  
     this.bbb = bbb;  
   }  
   @Autowired  
   public void setCcc(C ccc) {  
     System.out.println("setting A.ccc with " + ccc);  
     this.ccc = ccc;  
   }  
 }  

然后，我们就可以从applicationContext.xml中移除下面的配置

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">property name</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bbb"</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> ref</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bBean"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">
<</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">property name</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"ccc"</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> ref</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"cBean"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></code>

移除之后，我们的applicationContext.xml配置文件就简化为下面的样子了

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx.B"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>
</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"cBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx.C"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>
</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"aBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.yyy.A"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></code>

当我们加载applicationContext.xml配置文件之后，将得到下面的结果：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@5e5a50
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@54a328
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@a3d4cf</span></code>

OK, 结果是错误的的，究竟是因为什么呢？为什么我们的属性没有被注入进去呢？

是因为注解本身并不能够做任何事情，它们只是最基本的组成部分，我们需要能够处理这些注解的处理工具来处理这些注解

这就是<context:annotation-config> 所做的事情

我们将applicationContext.xml配置文件作如下修改：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span style="color: rgb(255, 0, 0);"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">annotation</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">config </span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">
<span style="color: rgb(255, 0, 0);"><</span></span><span style="color: rgb(255, 0, 0);"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"bBean"</span><span class="kwd" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx.B"</span></span><span style="color: rgb(255, 0, 0);"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>
</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"cBean"</span><span class="kwd" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx.C"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">
<span style="color: rgb(255, 0, 0);"><</span></span><span style="color: rgb(255, 0, 0);"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"aBean"</span><span class="kwd" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.yyy.A"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></span></code>

当我们加载applicationContext.xml配置文件之后，将得到下面的结果：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@15663a2
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@cd5f8b
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@157aa53
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bbb with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@15663a2
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">ccc with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@cd5f8b</span></code>

OK, 结果正确了。

下面演示<context:annotation-config> 跟 <context:component-scan>区别：

但是如果我们将代码作如下修改：

[java]view plaincopy 
    
 package com.xxx;  
 import org.springframework.stereotype.Component;  
 @Component  
 public class B {  
   public B() {  
     System.out.println("creating bean B: " + this);  
   }  
 }  
   
 package com.xxx;  
 import org.springframework.stereotype.Component;  
 @Component  
 public class C {  
   public C() {  
     System.out.println("creating bean C: " + this);  
   }  
 }  
   
 package com.yyy;  
 import org.springframework.beans.factory.annotation.Autowired;  
 import org.springframework.stereotype.Component;  
 import com.xxx.B;  
 import com.xxx.C;  
 @Component  
 public class A {   
   private B bbb;  
   private C ccc;  
   public A() {  
     System.out.println("creating bean A: " + this);  
   }  
   @Autowired  
   public void setBbb(B bbb) {  
     System.out.println("setting A.bbb with " + bbb);  
     this.bbb = bbb;  
   }  
   @Autowired  
   public void setCcc(C ccc) {  
     System.out.println("setting A.ccc with " + ccc);  
     this.ccc = ccc;  
   }  
 }  

applicationContext.xml配置文件修改为：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">annotation</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">config </span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></code>

当我们加载applicationContext.xml配置文件之后，却没有任何输出，这是为什么呢？

那是因为<context:annotation-config />仅能够在已经在已经注册过的bean上面起作用。

对于没有在spring容器中注册的bean，它并不能执行任何操作。

但是不用担心，<context:component-scan>除了具有<context:annotation-config />的功能之外，还具有自动将带有@component,@service,@Repository等注解的对象注册到spring容器中的功能。

我们将applicationContext.xml配置文件作如下修改：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></code>

当我们加载applicationContext.xml的时候，会得到下面的结果：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@1be0f0a
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@80d1ff</span></code>

这是什么原因呢？

是因为我们仅仅扫描了com.xxx包及其子包的类，而class A是在com.yyy包下，所以就扫描不到了

下面我们在applicationContext.xml中把com.yyy也加入进来：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span style="color: rgb(255, 0, 0);"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx"</span></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><span style="color: rgb(255, 0, 0);">/>

</span></span></code><span style="color: rgb(255, 0, 0);"><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">"com.xxx,com.yyy"</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">/></span></span>

然后加载applicationContext.xml就会得到下面的结果：<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"></code>

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@cd5f8b
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@15ac3c9
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@ec4a87
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bbb with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@cd5f8b
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">ccc with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@15ac3c9</span></code>

哇，结果正确啦！

回头看下我们的applicationContext.xml文件，已经简化为：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>

</span></code><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="font-family: 'Courier New', Courier, monospace; color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="font-family: 'Courier New', Courier, monospace; color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">"com.xxx,com.yyy"</span><span class="pun" style="font-family: 'Courier New', Courier, monospace; border: 0px; padding: 0px; margin: 0px; font-size: 1em; vertical-align: baseline; background-color: transparent;">/></span>

了。

那如果我们在applicationContext.xml手动加上下面的配置，也就是说既在applicationContext.xml中手动的注册了A的实例对象，同时，通过component-scan去扫描并注册B,C的对象

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span style="color: rgb(255, 0, 0);"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx"</span></span><span style="color: rgb(255, 0, 0);"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/>
</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"aBean"</span><span class="kwd" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.yyy.A"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></span></code>

结果仍是正确的:

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@157aa53
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@ec4a87
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@1d64c37
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bbb with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@157aa53
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">ccc with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@ec4a87</span></code>

虽然class A并不是通过扫描的方式注册到容器中的，但是<context:component-scan> 所产生的的处理那些注解的处理器工具，会处理所有绑定到容器上面的bean，不管是通过xml手动注册的还是通过scanning扫描注册的。

那么，如果我们通过下面的方式呢？我们既配置了<context:annotation-config />，又配置了<context:component-scan base-package="com.xxx" />，它们都具有处理在容器中注册的bean里面的注解的功能。会不会出现重复注入的情况呢？

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">annotation</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">config </span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">context</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">component</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">scan base</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">-</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">package</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.xxx"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"><</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bean id</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"aBean"</span><span class="kwd" style="color: rgb(0, 0, 139); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">class</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">=</span><span class="str" style="color: rgb(128, 0, 0); border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">"com.yyy.A"</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">/></span></code>

不用担心，不会出现的：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@157aa53
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@ec4a87
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@1d64c37
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bbb with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@157aa53
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">ccc with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@ec4a87</span></code>

因为<context:annotation-config />和 <context:component-scan>同时存在的时候，前者会被忽略。也就是那些@autowire，@resource等注入注解只会被注入一次

哪怕是你手动的注册了多个处理器，spring仍然只会处理一次：

[xml]view plaincopy 
    
 <context:annotation-config />  
 <context:component-scan base-package="com.xxx" />  
 <bean id="aBean" class="com.yyy.A" />  
 <bean id="bla" class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />  
 <bean id="bla1" class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />  
 <bean id="bla2" class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />  
 <bean id="bla3" class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />  

结果仍是正确的：

<code style="border: 0px; padding: 0px; margin: 0px; font-family: Consolas, Menlo, Monaco, 'Lucida Console', 'Liberation Mono', 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', 'Courier New', monospace, serif; vertical-align: baseline;"><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">creating bean B</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@157aa53
creating bean C</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@ec4a87
creating bean A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">:</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;"> com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">yyy</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">A@25d2b2
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">bbb with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">B@157aa53
setting A</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">ccc with com</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">xxx</span><span class="pun" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">.</span><span class="pln" style="border: 0px; padding: 0px; margin: 0px; vertical-align: baseline; background-color: transparent;">C@ec4a87</span></code>