注入属性值
               通过PropertyPathFactoryBean类，可以注入某个实例的属性值。PropertyPathFactoryBean用来获取目标bean的属性值。获得的值可注入给其他bean,也可以直接定义成新的bean.
            看例子：
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package org.viking.spring.imp;

public class Person
{
 private int age;
 
 private Son son;

 public void setAge(int age) {
  this.age = age;
 }

 public void setSon(Son son) {
  this.son = son;
 }

 public int getAge() {
  return age;
 }

 public Son getSon() {
  return son;
 }
 
}
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package org.viking.spring.imp;

public class Son
{
 private int age;

 public void setAge(int age) {
  this.age = age;
 }

 public int getAge() {
  return age;
 }
}
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<?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-2.0.xsd">
 <bean id="person" class="org.viking.spring.imp.Person" scope="prototype">
  <property name="age">
   <value>30</value>
  </property>
  <property name="son">
   <bean class="org.viking.spring.imp.Son">
    <property name="age">
     <value>11</value>
    </property>
   </bean>
  </property>
 </bean>
 
 <bean id="son2" class="org.viking.spring.imp.Son">
  <property name="age">
   <bean id="person.son.age" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
   </bean>
  </property>
 </bean>

</beans>
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package org.viking.spring.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.viking.spring.imp.Son;

import junit.framework.TestCase;

public class testInject extends TestCase
{
 public void testInjectAttribute()
 {
  ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
  System.out.println("son2的age属性值：" + ((Son)app.getBean("son2")).getAge());
}
}

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        一个bean实例的属性值，不仅可以注入另一个bean,还可将bean实例的属性值直接定义成bean实例，也是通过PropertyPathFactoryBean完成的。对上面ApplicationContext.xml文件做下修改！
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<?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-2.0.xsd">
 <bean id="person" class="org.viking.spring.imp.Person" scope="prototype">
  <property name="age">
   <value>30</value>
  </property>
  <property name="son">
   <bean class="org.viking.spring.imp.Son">
    <property name="age">
     <value>11</value>
    </property>
   </bean>
  </property>
 </bean>
 
 <bean id="son2" class="org.viking.spring.imp.Son">
  <property name="age">
   <bean id="person.son.age" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
   </bean>
  </property>
 </bean>
 
 <bean id="son1" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
  <property name="targetBeanName">
   <value>person</value>
  </property>
  <property name="propertyPath">
   <value>son</value>
  </property>
 </bean>
</beans>
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package org.viking.spring.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.viking.spring.imp.Son;

import junit.framework.TestCase;

public class testInject extends TestCase
{
 public void testInjectAttribute()
 {
  ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
  System.out.println("son2的age属性值：" + ((Son)app.getBean("son2")).getAge());
  System.out.println("系统获取的SON1：" + app.getBean("son1"));

}
}
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    使用PropertyPathFactoryBean必须指定以下两个属性。
        1.targetBeanName:用于指定目标bean,确定获取哪个bean的属性值。
        2.propertyPath：用于指定属性，确定获取目标bean的哪个属性值，此处的属性可直接使用属性表达式。
       可以将基本数据类型的属性值定义成bean实例。在配置文件中再增加如下代码：
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<?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-2.0.xsd">
 <bean id="person" class="org.viking.spring.imp.Person" scope="prototype">
  <property name="age">
   <value>30</value>
  </property>
  <property name="son">
   <bean class="org.viking.spring.imp.Son">
    <property name="age">
     <value>11</value>
    </property>
   </bean>
  </property>
 </bean>
 
 <bean id="son2" class="org.viking.spring.imp.Son">
  <property name="age">
   <bean id="person.son.age" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
   </bean>
  </property>
 </bean>
 
 <bean id="son1" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
  <property name="targetBeanName">
   <value>person</value>
  </property>
  <property name="propertyPath">
   <value>son</value>
  </property>
 </bean>
 
 <bean id="theAge" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
  <property name="targetBeanName">
   <value>person</value>
  </property>
  <property name="propertyPath">
   <value>son.age</value>
  </property>
 </bean>
</beans>
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package org.viking.spring.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.viking.spring.imp.Son;

import junit.framework.TestCase;

public class testInject extends TestCase
{
 public void testInjectAttribute()
 {
  ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
  System.out.println("son2的age属性值：" + ((Son)app.getBean("son2")).getAge());
  System.out.println("系统获取的SON1：" + app.getBean("son1"));
  System.out.println("系统获取的theAge的值：" + app.getBean("theAge"));

}
}
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        目标bean既可以是容器中已有的bean实例，也可以是嵌套bean实例。
-----------------------------------------------------------------------------------------
<?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-2.0.xsd">
 <bean id="person" class="org.viking.spring.imp.Person" scope="prototype">
  <property name="age">
   <value>30</value>
  </property>
  <property name="son">
   <bean class="org.viking.spring.imp.Son">
    <property name="age">
     <value>11</value>
    </property>
   </bean>
  </property>
 </bean>
 
 <bean id="son2" class="org.viking.spring.imp.Son">
  <property name="age">
   <bean id="person.son.age" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
   </bean>
  </property>
 </bean>
 
 <bean id="son1" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
  <property name="targetBeanName">
   <value>person</value>
  </property>
  <property name="propertyPath">
   <value>son</value>
  </property>
 </bean>
 
 <bean id="theAge" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
  <property name="targetBeanName">
   <value>person</value>
  </property>
  <property name="propertyPath">
   <value>son.age</value>
  </property>
 </bean>
 
 <bean id="theAge2" class="org.springframework.beans.factory.config.PropertyPathFactoryBean">
  <property name="targetObject"><!-- 要注意，这里不是targetBeanName了噢！ -->
   <bean class="org.viking.spring.imp.Person">
    <property name="age">
     <value>12</value>
    </property>
   </bean>
  </property>
  <property name="propertyPath">
   <value>age</value>
  </property>
 </bean>
 
</beans>
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package org.viking.spring.test;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.viking.spring.imp.Son;

import junit.framework.TestCase;

public class testInject extends TestCase
{
 public void testInjectAttribute()
 {
  ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
  System.out.println("son2的age属性值：" + ((Son)app.getBean("son2")).getAge());
  System.out.println("系统获取的SON1：" + app.getBean("son1"));
  System.out.println("系统获取的theAge的值：" + app.getBean("theAge"));
  System.out.println("系统获取的theAge2的值：" + app.getBean("theAge2"));
 }
}
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        注意上面配置文件，定义嵌套bean实例时采用的时targetObject，而不时targetBeanName，如果这填错了，可是要报异常的噢！


-------以上的文字以及代码摘录于李刚写的《轻量级J2EE开发企业应用实战》，代码有少许变动！

Identify the aspects of your application that vary and separate them from what stays the same.