Spring中基于FactoryBean的练习-蒲公英云

Spring中基于FactoryBean的练习

1.BeanFactory，
以Factory结尾，表示它是一个工厂类(接口)，用于管理Bean的一个工厂。在Spring中，BeanFactory是IOC容器的核心接口，它的职责包括：实例化、定位、配置应用程序中的对象及建立这些对象间的依赖。
　　Spring为我们提供了许多易用的BeanFactory实现，XmlBeanFactory就是常用的一个，该实现将以XML方式描述组成应用的对象及对象间的依赖关系。XmlBeanFactory类将持有此XML配置元数据，并用它来构建一个完全可配置的系统或应用。
2.FactoryBean
以Bean结尾，表示它是一个Bean，不同于普通Bean的是：它是实现了FactoryBean接口的Bean，根据该Bean的ID从BeanFactory中获取的实际上是FactoryBean的getObject()返回的对象，而不是FactoryBean本身，如果要获
取FactoryBean对象，请在id前面加一个&符号来获取。

请参考如下代码：

//ABean.java
package sping.analysis.beans;
public class ABean implements MyBean { 
    private String name;
    public ABean(String name) { 
        this.name = name;
    }
    public void doSomething() { 
        System.out.println(this.name);
    }
}
//MyBean.java
package sping.analysis.beans;
public interface MyBean { 
    void doSomething();
}
//MyFactoryBean.java
package sping.analysis.beans;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class MyFactoryBean implements FactoryBean<Object>, InitializingBean, DisposableBean { 
    @Value(value = "sping.analysis.beans.MyBean")
    private String interfaceName;
    @Autowired(required=false) @Qualifier("aBean")
    private Object target;
    private Object proxyObj;
    public void destroy() throws Exception { 
        System.out.println(this.getClass().getName() + ".destroy() ....");
    }
    /** * 注意： * JDK Proxy 动态代理是基于 接口 来实现的。 * cglib 才是基于类实现的 */
    public void afterPropertiesSet() throws Exception { 
        System.out.println(this.getClass().getName() + ".afterPropertiesSet() ...");
        proxyObj = Proxy.newProxyInstance(
                this.getClass().getClassLoader(),
                new Class[] { Class.forName(interfaceName)},
                new InvocationHandler() { 
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { 
                        System.out.println("invoke method:" + method.getName());
                        Object res = method.invoke(target, args);
                        return res;
                    }
                });
    }
    public Object getObject() throws Exception { 
        System.out.println(this.getClass().getName() + ".getObject() ...");
        return proxyObj;
    }
    public Class<?> getObjectType() { 
        return proxyObj == null ? Object.class : proxyObj.getClass();
    }
}
//TestFactoryBean.java
package sping.analysis.beans;
import javax.annotation.Resource;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:application3.xml")
public class TestFactoryBean { 
    @Resource(name = "myFactoryBean")
    private MyBean myBean;
    //如果要获取FactoryBean对象，请在id前面加一个&符号来获取
    @Resource(name = "&myFactoryBean")
    private MyFactoryBean myFactoryBean;
    @Test
    public void test() { 
        myBean.doSomething();
        System.out.println("> myFactoryBean.isSingleton:" + myFactoryBean.isSingleton());
    }
}

输出结果：

sping.analysis.beans.MyFactoryBean.afterPropertiesSet() ...
sping.analysis.beans.MyFactoryBean.getObject() ...
invoke method:doSomething
张三
> myFactoryBean.isSingleton:true
sping.analysis.beans.MyFactoryBean.destroy() ....
//application3.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
    <context:component-scan base-package="sping.analysis.beans"/>
    <bean id="aBean" class="sping.analysis.beans.ABean">
        <constructor-arg type="java.lang.String" value="张三" />
    </bean>
</beans>