Spring实战之使用静态工厂方法创建Bean操作示例

<?xml version="1.0" encoding="GBK"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns="http://www.springframework.org/schema/beans"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-4.0.xsd">
   <!-- 下面配置驱动Spring调用BeingFactory的静态getBeing()方法来创建Bean
   该bean元素包含的constructor-arg元素用于为静态工厂方法指定参数，
   因此这段配置会驱动Spring以反射方式来执行如下代码：
   dog = org.crazyit.app.factory.BeingFactory.getBeing("dog"); -->
   <bean id="dog" class="org.crazyit.app.factory.BeingFactory"
      factory-method="getBeing">
      <!-- 配置静态工厂方法的参数 -->
      <constructor-arg value="dog"/>
      <!-- 驱动Spring以"我是狗"为参数来执行dog的setMsg()方法 -->
      <property name="msg" value="我是狗"/>
   </bean>
   <!-- 下面配置会驱动Spring以反射方式来执行如下代码：
   dog = org.crazyit.app.factory.BeingFactory.getBeing("cat"); -->
   <bean id="cat" class="org.crazyit.app.factory.BeingFactory"
      factory-method="getBeing">
      <!-- 配置静态工厂方法的参数 -->
      <constructor-arg value="cat"/>
      <!-- 驱动Spring以"我是猫"为参数来执行dog的setMsg()方法 -->
      <property name="msg" value="我是猫"/>
   </bean>
</beans>

package org.crazyit.app.service;
public interface Being
{
   public void testBeing();
}

package org.crazyit.app.service.impl;
import org.crazyit.app.service.*;
public class Cat implements Being
{
   private String msg;
   // msg的setter方法
   public void setMsg(String msg)
   {
      this.msg = msg;
   }
   // 实现接口必须实现的testBeing方法
   public void testBeing()
   {
      System.out.println(msg +
        "，猫喜欢吃老鼠");
   }
}

package org.crazyit.app.service.impl;
import org.crazyit.app.service.*;
public class Dog implements Being
{
   private String msg;
   // msg的setter方法
   public void setMsg(String msg)
   {
      this.msg = msg;
   }
   // 实现接口必须实现的testBeing()方法
   public void testBeing()
   {
      System.out.println(msg +
        "，狗爱啃骨头");
   }
}

package org.crazyit.app.factory;
import org.crazyit.app.service.impl.*;
import org.crazyit.app.service.*;
public class BeingFactory
{
  // 返回Being实例的静态工厂方法
  // arg参数决定返回哪个Being类的实例
  public static Being getBeing(String arg)
  {
    // 调用此静态方法的参数为dog，则返回Dog实例
    if (arg.equalsIgnoreCase("dog"))
    {
      return new Dog();
    }
    // 否则返回Cat实例
    else
    {
      return new Cat();
    }
  }
}

package lee;
import org.springframework.context.*;
import org.springframework.context.support.*;
import org.crazyit.app.service.*;
public class SpringTest
{
  public static void main(String[] args)
  {
    // 以类加载路径下的配置文件创建ClassPathResource实例
    ApplicationContext ctx = new
      ClassPathXmlApplicationContext("beans.xml");
    Being b1 = ctx.getBean("dog" , Being.class);
    b1.testBeing();
    Being b2 = ctx.getBean("cat" , Being.class);
    b2.testBeing();
  }
}