SpringMvc三层架构注解详解@Controller、@Service和@Repository

最新推荐文章于 2023-11-26 20:38:49 发布

转载最新推荐文章于 2023-11-26 20:38:49 发布 · 794 阅读

本文详细介绍了SpringMvc三层架构的注解。SpringMvc采用三层分层控制结构，在持久层、业务层和控制层分别用@Repository、@Service、@Controller注解类。文中阐述了各注解的作用、使用方式，如@Controller标记的类需交给Spring管理，@Service默认按名称装配等。

SpringMvc三层架构注解详解@Controller、@Service和@Repository

2018年11月24日 22:30:06 Coding-Monkey 阅读数：1976 标签： @Controller SpringMvc @Service @Repository更多

个人分类： SpringMVC

springvmc采用经典的三层分层控制结构，在持久层，业务层和控制层分别采用@Repository、@Service、@Controller对分层中的类进行注解，而@Component对那些比较中立的类进行注解

1. @Controller控制层

@Controller用于标记在一个类上，使用它标记的类就是一个SpringMvc Controller对象，分发处理器会扫描使用该注解的类的方法，并检测该方法是否使用了@RequestMapping注解。
@Controller只是定义了一个控制器类，而使用@RequestMapping注解的方法才是处理请求的处理器。
@Controller标记在一个类上还不能真正意义上说它就是SpringMvc的控制器，应为这个时候Spring还不认识它，这个时候需要把这个控制器交给Spring来管理。有两种方式可以管理：

<span style="color:#000000"><code class="language-xml"><span style="color:#969896"><!--基于注解的装配--></span>
<span style="color:#969896"><!--方式一--></span>
<span style="color:#cc6666"><span style="color:#cc6666"><span style="color:#999999"><</span>bean</span> <span style="color:#cc6666">class</span><span style="color:#b5bd68"><span style="color:#999999">=</span><span style="color:#999999">"</span>com.HelloWorld<span style="color:#999999">"</span></span><span style="color:#999999">/></span></span>
<span style="color:#969896"><!--方式二--></span>
<span style="color:#969896"><!--路径写到controller的上一层--></span>
<span style="color:#cc6666"><span style="color:#cc6666"><span style="color:#999999"><</span>context:component-scan</span> <span style="color:#cc6666">base-package</span><span style="color:#b5bd68"><span style="color:#999999">=</span><span style="color:#999999">"</span>com<span style="color:#999999">"</span></span><span style="color:#999999">/></span></span>
</code></span>

Action层:

<span style="color:#000000"><code class="language-java"><span style="color:#b294bb">package</span> com<span style="color:#999999">;</span>
<span style="color:#999999">@Controller</span>
<span style="color:#b294bb">public</span> <span style="color:#b294bb">class</span> HelloWorld<span style="color:#999999">{</span>
	
	<span style="color:#999999">@RequestMapping</span><span style="color:#999999">(</span>value<span style="color:#a67f59">=</span><span style="color:#b5bd68">"/showRegUser"</span><span style="color:#999999">)</span>
	<span style="color:#b294bb">public</span> String <span style="color:#81a2be">printHello</span><span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#999999">{</span>
		<span style="color:#b294bb">return</span> <span style="color:#b5bd68">"hello"</span><span style="color:#999999">;</span>
	<span style="color:#999999">}</span>

    <span style="color:#999999">@Autowried</span>
    <span style="color:#b294bb">private</span> IocSerevce service<span style="color:#999999">;</span>
    <span style="color:#b294bb">public</span> <span style="color:#b294bb">void</span> <span style="color:#81a2be">add</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        service<span style="color:#999999">.</span><span style="color:#81a2be">add</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span>

component-scan默认扫描的注解类型是@Component,不过，在@Component的语义基础之上细化为@Reposity，@Service,@Controller.
有一个use-defaultbao'i-filters属性，属性默认是true,表示会扫描抱下所有的标有@Component的类，并注册为bean，也就是@Component的子注解@Service,@reposity等
如果只想扫描包下的@Controller或其他内容，则设置use-default-filters属性为false，表示不再按照scan指定的包进行扫描，而是按照指定包进行扫描

<span style="color:#000000"><code class="language-xml"><span style="color:#cc6666"><span style="color:#cc6666"><span style="color:#999999"><</span>context:component-scan</span> <span style="color:#cc6666">base-package</span><span style="color:#b5bd68"><span style="color:#999999">=</span><span style="color:#999999">"</span>com<span style="color:#999999">"</span></span> <span style="color:#cc6666">user-default-filters</span><span style="color:#b5bd68"><span style="color:#999999">=</span><span style="color:#999999">"</span>false<span style="color:#999999">"</span></span><span style="color:#999999">></span></span>
    <span style="color:#cc6666"><span style="color:#cc6666"><span style="color:#999999"><</span>context:include-filter</span> <span style="color:#cc6666">type</span><span style="color:#b5bd68"><span style="color:#999999">=</span><span style="color:#999999">"</span>regex<span style="color:#999999">"</span></span> <span style="color:#cc6666">expression</span><span style="color:#b5bd68"><span style="color:#999999">=</span><span style="color:#999999">"</span>com.tan.*<span style="color:#999999">"</span></span><span style="color:#999999">/></span></span>
<span style="color:#cc6666"><span style="color:#cc6666"><span style="color:#999999"></</span>context:component-scan</span><span style="color:#999999">></span></span>
</code></span>

当没有设置use-default-filters属性或属性为true时，表示基于base-package包下指定扫描的具体路径。

2. @Service()

此注注解属于业务逻辑层，service或者manager层
默认按照名称进行装配，如果名称可以通过name属性指定，如果没有name属性，注解写在字段上时，默认去字段名进行查找，如果注解写在setter方法上，默认按照方法属性名称进行装配。当找不到匹配的bean时，才按照类型进行装配，如果name名称一旦指定就会按照名称进行装配
Service层：

<span style="color:#000000"><code class="language-java"><span style="color:#999999">@Service</span><span style="color:#999999">(</span><span style="color:#999999">)</span>
<span style="color:#b294bb">public</span> <span style="color:#b294bb">class</span> IocService<span style="color:#999999">{</span>

    <span style="color:#999999">@Resource</span>
    <span style="color:#b294bb">private</span> IIocDao iiocDao<span style="color:#999999">;</span>
    <span style="color:#b294bb">public</span> <span style="color:#b294bb">void</span> <span style="color:#81a2be">add</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        iiocDao<span style="color:#999999">.</span><span style="color:#81a2be">add</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span>

3. @Repository持久层

此注解式持久层组件，用于标注数据访问组件，即DAO组件
DAO层
先定义一个接口

<span style="color:#000000"><code class="language-java"><span style="color:#b294bb">public</span> <span style="color:#b294bb">interface</span> IIocDao<span style="color:#999999">{</span>
    <span style="color:#b294bb">public</span> <span style="color:#b294bb">void</span> <span style="color:#81a2be">add</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
<span style="color:#999999">}</span>
</code></span>

然后实现类

<span style="color:#000000"><code class="language-java"><span style="color:#969896">//Dao层中定义了一些接口</span>
<span style="color:#969896">//表示将Dao类声明为bean</span>
<span style="color:#999999">@Repository</span>
<span style="color:#b294bb">public</span> <span style="color:#b294bb">class</span> IocDao <span style="color:#b294bb">implements</span> IIocDao<span style="color:#999999">{</span>
    <span style="color:#b294bb">public</span> <span style="color:#b294bb">void</span> <span style="color:#81a2be">add</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">{</span>
        System<span style="color:#999999">.</span>out<span style="color:#999999">.</span><span style="color:#81a2be">println</span><span style="color:#999999">(</span><span style="color:#b5bd68">"调用了Dao"</span><span style="color:#999999">)</span><span style="color:#999999">;</span>
    <span style="color:#999999">}</span>
<span style="color:#999999">}</span>
</code></span>

另外一种解释： @Repository对应数据访问层Bean

<span style="color:#000000"><code class="language-java"><span style="color:#999999">@Repository</span><span style="color:#999999">(</span>value<span style="color:#a67f59">=</span><span style="color:#b5bd68">"userDao"</span><span style="color:#999999">)</span>
<span style="color:#b294bb">public</span> <span style="color:#b294bb">class</span> UserDaoImpl <span style="color:#b294bb">extends</span> BeansDaoImpl<span style="color:#81a2be"><span style="color:#999999"><</span>User<span style="color:#999999">></span></span><span style="color:#999999">{</span>
    <span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span><span style="color:#999999">.</span>
<span style="color:#999999">}</span>
</code></span>

@Repository(value=“userDao”)注解告诉Spring ,让Spring创建一个名字叫做"userDao"的UserDapImpl实例。
当Service需要使用Spring创建的名字叫“userDao”的UserDaoImpl实例时，就可以使用@Resource(name=“userDao”)注解告诉Spring,Spring把创建好的userDao注入给Service即可。

<span style="color:#000000"><code class="language-java"> <span style="color:#969896">//注入userDao，从数据库中根据用户Id取出指定用户时需要用到</span>
 <span style="color:#999999">@Resource</span><span style="color:#999999">(</span>name <span style="color:#a67f59">=</span> <span style="color:#b5bd68">"userDao"</span><span style="color:#999999">)</span>
 <span style="color:#b294bb">private</span> BaseDao<span style="color:#81a2be"><span style="color:#999999"><</span>User<span style="color:#999999">></span></span> userDao<span style="color:#999999">;</span>
</code></span>

参考文章:https://www.cnblogs.com/xdp-gacl/p/3495887.html