FieldRetrievingFactoryBean 和 MethodInvokingFactoryBean

spring提供了filed的值注入和method的返回值注入。

1、Field值的注入

filed值注入需要使用org.springframework.beans.factory.config.FieldRetrievingFactoryBean来获取类的静态变量。

例如，我们通常在接口中定义常量：

view plaincopy to clipboardprint?package com.baobaotao.fb;
public interface CarBrandType {
    String HONG_QI = "红旗";
    String JI_LI = "吉利";
}
package com.baobaotao.fb;
public interface CarBrandType {
    String HONG_QI = "红旗";
    String JI_LI = "吉利";
}

下面利用FieldRetrievingFactoryBean获取CarBandType接口中定义的常量，并注入到某个bean的属性中：

view plaincopy to clipboardprint?<bean id="car" class="com.baobaotao.fb.Car">
    <property name="brand" ref="hongQi"/>
</bean>
<bean id="hongQi" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean"
    <property name="staticField" value="com.baobaotao.fb.CarBrandType.HONG_QI"/>
</bean>
<bean id="car" class="com.baobaotao.fb.Car">
    <property name="brand" ref="hongQi"/>
</bean>
<bean id="hongQi" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean"
    <property name="staticField" value="com.baobaotao.fb.CarBrandType.HONG_QI"/>
</bean>



Spring还允许用户用常量的全限定名作为FieldRetrievingFactoryBean的id，其效果和通过配置staticField属性是一样的：

view plaincopy to clipboardprint?<bean id="car" class="com.baobaotao.fb.Car">
    <property name="brand" ref="com.baobaotao.fb.CarBrandType.HONG_QI"/>
</bean>
<bean id="com.baobaotao.fb.CarBrandType.HONG_QI" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean" />
<bean id="car" class="com.baobaotao.fb.Car">
    <property name="brand" ref="com.baobaotao.fb.CarBrandType.HONG_QI"/>
</bean>
<bean id="com.baobaotao.fb.CarBrandType.HONG_QI" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean" />



当然，也可以直接将FieldRetrievingFactoryBean以内置bean的方式对brand属性进行赋值，这样在配置上更紧凑一些：

view plaincopy to clipboardprint?<bean id="car" class="com.baobaotao.fb.Car">
    <property name="brand">
        <bean id="com.baobaotao.fb.CarBrandType.HONG_QI" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean">
        </bean>
    </property>
</bean>
<bean id="car" class="com.baobaotao.fb.Car">
    <property name="brand">
        <bean id="com.baobaotao.fb.CarBrandType.HONG_QI" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean">
        </bean>
    </property>
</bean>




2、Method返回值的注入
Method返回值的注入需要使用MethodInvokingFactoryBean来完成。

在xml配置中，需要设定targetObject和targetMethod来指定目标bean和方法。如果使用静态方法，则需要指定targetClass和targetMethod

配置文件如下：

view plaincopy to clipboardprint?<bean id="bdog" class="com.baobaotao.fb.Dog">
  <property name="age">
    <bean class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
      <property name="targetObject">
        <ref local="randomAge"/>
      </property>
      <property name="targetMethod">
        <value>getAge</value>
      </property>
    </bean>
  </property>
</bean>
<bean id="randomAge" class="com.baobaotao.fd.RandomAge" />
<bean id="bdog" class="com.baobaotao.fb.Dog">
  <property name="age">
    <bean class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
      <property name="targetObject">
        <ref local="randomAge"/>
      </property>
      <property name="targetMethod">
        <value>getAge</value>
      </property>
    </bean>
  </property>
</bean>
<bean id="randomAge" class="com.baobaotao.fd.RandomAge" />


对于静态方法：

view plaincopy to clipboardprint?<bean id="bdog" class="com.baobaotao.fb.Dog">
  <property name="age">
    <bean class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
      <property name="targetClass">
        <value>com.baobaotao.fb.RandomAge</value>
      </property>
      <property name="targetMethod">
        <!-- getAge必须是静态方法 -->
        <value>getAges</value>
      </property>
    </bean>
  </property>
</bean>