Spring受管Bean依賴注入（設值注入）

設值注入是Spring支持的多種依賴注入類型中的一種，也是最爲常見的一種。設值（setter）注入指在通過調用無參構造器（或無參靜態工廠方法，或工廠Bean的蜚靜態工廠方法）實例化受管Bean後調用setter方法，從而建立起對象之間的依賴關係。

一、無參構造器實例化受管Bean

public class HelloWorld implements IHelloWorld {

    protected static final Log log = LogFactory.getLog(HelloWorld.class);
    private IHelloStr helloStr;

    public HelloWorld() {
        super();
    }
    public void setHelloStr(IHelloStr str) {
        this.helloStr = str;
    }
    public String getContent() {
        return helloStr.getContent();
    }
}

<?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-2.5.xsd">
    <bean name="fileHello" class="test.FileHelloStrImpl">
        <constructor-arg>
            <value>helloworld.properties</value>
        </constructor-arg>
    </bean>
    <bean id="helloWorld" class="test.HelloWorld">
        <property name="helloStr" ref="fileHello" />
    </bean>
</beans>

我們可以通過ref屬性指定依賴的對象或value屬性直接給出目標對象。

二、無參靜態工廠方法實例化受管Bean

如果希望通過調用無參靜態工廠方法獲得天受管Bean，則需要往對應的POJO類中添加靜態方法以，以下爲實例：

public class HelloWorld implements IHelloWorld {

    protected static final Log log = LogFactory.getLog(HelloWorld.class);
    private IHelloStr helloStr;
    public void setHelloStr(IHelloStr str) {
        this.helloStr = str;
    }
    public String getContent() {
        return helloStr.getContent();
    }

    public static HelloWorld getHelloWorld(){
        return new HelloWorld();
    }
}

<?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-2.5.xsd">
     <bean id="helloWorld"  factory-method="getHelloWorld"
          class="test.HelloWorld">
          <property name="helloStr" ref="fileHello"/>
     </bean>

     <bean name="fileHello" class="test.FileHelloStrImpl">
          <constructor-arg>
               <value>helloworld.properties</value>
          </constructor-arg>
     </bean>

</beans>

三、工廠Bean的非靜態工廠方法實例受管Bean

同樣的如果希望通過調用工廠Bean的非靜態工廠方法獲得受管Bean，則需要往對應的POJO類中添加非靜態方法以，實例如下：

public class HelloWorld implements IHelloWorld {

    protected static final Log log = LogFactory.getLog(HelloWorld.class);
    private IHelloStr helloStr;
    public void setHelloStr(IHelloStr str) {
        this.helloStr = str;
    }
    public String getContent() {
        return helloStr.getContent();
    }

    public HelloWorld makeHelloWorld(){
        return new HelloWorld();
    }
}

<?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-2.5.xsd">
     <bean id="helloWorldFactory" class="test.HelloWorld"/>

     <bean id="helloWorld" factory-bean="helloWorldFactory"
            factory-method="makeHelloWorld">
          <property name="helloStr" ref="fileHello"/>
     </bean>

     <bean name="fileHello"
          class="test.FileHelloStrImpl">
          <constructor-arg>
               <value>helloworld.properties</value>
          </constructor-arg>
     </bean>

</beans>

配置的helloWorldFactory受管Bean扮演了工廠Bean的角色。

轉載自：http://blog.csdn.net/zhangxs_3/article/details/4345575