FieldRetrievingFactoryBean

FieldRetrievingFactoryBean

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>