重读 Spring 3 开发手册 总结 一

1. ApplicationContext基本配置：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
           
    <import resource="services.xml"/>
    <import resource="resources/messageSource.xml"/>
    <import resource="/resources/themeSource.xml"/>
    <import resource="../resources/configFile.xml"/>
    <import resource="classpath:../configFile.xml"/>
    
  <bean id="..." class="...">
    <!-- collaborators and configuration for this bean go here -->
  </bean>

  <bean id="..." class="...">
    <!-- collaborators and configuration for this bean go here -->
  </bean>
  <!-- more bean definitions go here -->
</beans>

2. 获取Container容器的实例

ApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"services.xml", "daos.xml"});
//or
ApplicationContext ctx = new FileSystemXmlApplicationContext("conf/appContext.xml");
//or
ApplicationContext ctx = new FileSystemXmlApplicationContext("classpath:conf/appContext.xml");

3. bean 实例化
1> 工厂静态方法实例化：
配置：

<!-- the factory bean, which contains a method called createInstance() -->
<bean id="serviceLocator" class="examples.DefaultServiceLocator">
 <!-- inject any dependencies required by this locator bean -->
</bean>
<!-- the bean to be created via the factory bean -->
<bean id="clientService" factory-bean="serviceLocator" factory-method="createClientServiceInstance"/>

类：

public class DefaultServiceLocator {
 private static ClientService clientService = new ClientServiceImpl();
 private DefaultServiceLocator() {}

 public ClientService createClientServiceInstance() {
    return clientService;
 }
}

2> 构造函数实例化：

1） 依赖关系：

package x.y;
public class Foo {
 public Foo(Bar bar, Baz baz) {
 // ...
 }
}

<beans>
 <bean id="foo" class="x.y.Foo">
 <constructor-arg ref="bar"/>
 <constructor-arg ref="baz"/>
 </bean>
 <bean id="bar" class="x.y.Bar"/>
 <bean id="baz" class="x.y.Baz"/>
</beans>

2）构造函数赋值:

package examples;
public class ExampleBean {
 private int years;
 private String ultimateAnswer;
 public ExampleBean(int years, String ultimateAnswer) {
 this.years = years;
 this.ultimateAnswer = ultimateAnswer;
 }
}

按类型

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg type="int" value="7500000"/>
<constructor-arg type="java.lang.String" value="42"/>
</bean>

按序列

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg index="0" value="7500000"/>
<constructor-arg index="1" value="42"/>
</bean>

按名称

<bean id="exampleBean" class="examples.ExampleBean">
<constructor-arg name="years" value="7500000"/>
<constructor-arg name="ultimateanswer" value="42"/>
</bean>

4 属性赋值：

<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
	<!-- results in a setDriverClassName(String) call -->
		<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
		<property name="url" value="jdbc:mysql://localhost:3306/mydb"/>
		<property name="username" value="root"/>
		<property name="password" value="masterkaoli"/>
	</bean>

或:

<bean id="myDataSource" class="org.apache.commons.dbcp.BasicDataSource"
      destroy-method="close"
      p:driverClassName="com.mysql.jdbc.Driver"
      p:url="jdbc:mysql://localhost:3306/mydb"
      p:username="root"
      p:password="masterkaoli"/>

或：

<bean id="mappings"
    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
	 <!-- typed as a java.util.Properties -->
	 <property name="properties">
		<value>
		   jdbc.driver.className=com.mysql.jdbc.Driver
		   jdbc.url=jdbc:mysql://localhost:3306/mydb
		</value>
	 </property>
	</bean>

集合类型的属性赋值：

<bean id="moreComplexObject" class="example.ComplexObject">
	<!-- results in a setAdminEmails(java.util.Properties) call -->
	<property name="adminEmails">
	  <props>
		  <prop key="administrator">administrator@example.org</prop>
		  <prop key="support">support@example.org</prop>
		  <prop key="development">development@example.org</prop>
	  </props>
	</property>
	<!-- results in a setSomeList(java.util.List) call -->
	<property name="someList">
	  <list>
		  <value>a list element followed by a reference</value>
		  <ref bean="myDataSource" />
	  </list>
	</property>
	<!-- results in a setSomeMap(java.util.Map) call -->
	<property name="someMap">
	  <map>
		  <entry key="an entry" value="just some string"/>
		  <entry key ="a ref" value-ref="myDataSource"/>
	  </map>
	</property>
	<!-- results in a setSomeSet(java.util.Set) call -->
	<property name="someSet">
	  <set>
		  <value>just some string</value>
		  <ref bean="myDataSource" />
	  </set>
	</property>
	</bean>

The value of a map key or value, or a set value, can also again be any of the following elements:
bean | ref | idref | list | set | map | props | value | null

集合类型的属性赋值及合并继承

<beans>
	<bean id="parent" abstract="true" class="example.ComplexObject">
	  <property name="adminEmails">
		  <props>
			  <prop key="administrator">administrator@example.com</prop>
			  <prop key="support">support@example.com</prop>
		  </props>
	  </property>
	</bean>
	<bean id="child" parent="parent">
	  <property name="adminEmails">
		  <!-- the merge is specified on the *child* collection definition -->
		  <props merge="true">
			  <prop key="sales">sales@example.com</prop>
			  <prop key="support">support@example.co.uk</prop>
		  </props>
	  </property>
	</bean>
	<beans>

child.getAdminEmails()结果为
=========================================
administrator=administrator@example.com
sales=sales@example.com
support=support@example.co.uk
=========================================


Null值和空值（Null and empty string values）

<bean class="ExampleBean">
     <property name="email" value=""/>
</bean>

等同于 exampleBean.setEmail("")；

<bean class="ExampleBean">
  <property name="email"><null/></property>
</bean>

等同于exampleBean.setEmail(null).

属性赋值的简写形式: p:namespace

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:p="http://www.springframework.org/schema/p"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
 <bean name="classic" class="com.example.ExampleBean">
 <property name="email" value="foo@bar.com"/>
 <property name="user" ref="aUser"/>
 </bean>

 <bean name="p-namespace" class="com.example.ExampleBean" p:email="foo@bar.com"/>
 <bean name="p-namespace-ref" class="com.example.ExampleBean" p:email="foo@bar.com" p:user-ref="aUser"/>
 
 <bean name="aUser" class="com.example.User">
 <property name="userName" value="tiger"/>
 <property name="age" value="24"/>
 </bean>
</beans>

构造函数的简写形式: c:namespace

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns:p="http://www.springframework.org/schema/c"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans.xsd">
 
 <bean id="bar" class="x.y.Bar"/>
 <bean id="baz" class="x.y.Baz"/>


 <-- 'traditional' declaration -->      
 <bean id="foo" class="x.y.Foo">
 <constructor-arg ref="bar"/>
 <constructor-arg ref="baz"/>
 <constructor-arg value="foo@bar.com"/>
 </bean>
 <-- 'c-namespace' declaration -->
 <bean id="foo" class="x.y.Foo" c:bar-ref="bar" c:baz-ref="baz" c:email="foo@bar.com">
</beans>

5 依赖
有多个依赖时可用逗号，空格，分号分割

<bean id="beanOne" class="ExampleBean" depends-on="manager,accountDao">
      <property name="manager" ref="manager" />
</bean>
<!--在beanOne实例化或消亡之前会先实例化或消亡manager和accountDao-->
<bean id="manager" class="ManagerBean" />
<bean id="accountDao" class="x.y.jdbc.JdbcAccountDao" />

有依赖关系的bean,不但在实例化时存在依赖关系，在对象消亡时也同样具有依赖关系。即在实例化或消亡时会先实例化或消亡被依赖对象。


6.Lazy-initialized 延时实例化
A lazy-initialized bean tells the IoC container to create a bean instance when it is first requested, rather than at startup.
延时实例化的bean,会在被访问的时候才进行实例化，而不是在容器启动是进行pre-instantiation

<bean id="lazy" class="com.foo.ExpensiveToCreateBean" lazy-init="true"/>

However, when a lazy-initialized bean is a dependency of a singleton bean that is not lazy-initialized, the ApplicationContext 

creates the lazy-initialized bean at startup, because it must satisfy the singleton's dependencies. 
The lazy-initialized bean is injected into a singleton bean elsewhere that is not lazy-initialized.
当一个singleton 的bean依赖于Lazy-initialized的bean时，Lazy-initialized将会被实例化。
Lazy-initialized同样可以作用于容器级别：

<beans default-lazy-init="true">
<!-- no beans will be pre-instantiated... -->
</beans>