(6)spring的动态代理

￡神魔★判官ぃ 2022-04-18 05:38 221阅读 0赞

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0haUEhZVA_size_16_color_FFFFFF_t_70][]

**代理(Proxy)是一种设计模式，通过访问代理对象访问目标对象，好处:可以在实现目标对象功能的基础上，增加额外的功能，并且不修改已经写好的代码。**

**代理类:**

public class LogProxy implements InvocationHandler{
    private Object target;
    	
    	public static Object getInstance(Object target) {
    		LogProxy LogProxy=new LogProxy();
    		LogProxy.target=target;
    		Object obj=Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), LogProxy);
    		//第三个参数是实现了InvocationHandler的对象
    		return obj;//返回代理对象
    	}
    	@Override
    	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    		// TODO 自动生成的方法存根】
    		
    		//只要一执行代理对象的方法，就会进入invoke方法
    		if(method.isAnnotationPresent(LogInfo.class)) {//判断该方法是否有annotation存在
    //(通过判断该方法的接口IUserDao)
    			LogInfo li=method.getAnnotation(LogInfo.class);//获取Annotation
    			Logger.info(new Date()+","+li.value());//获取Annotation的value
    		}
    		Object result=method.invoke(target, args);//执行的是目标对象target的方法
    		return result;//执行该方法的返回值
    	}
    
    }

**beans.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:annotation-config/>
    <context:component-scan base-package="spring"/>
    <bean id="UserDynamicDao" class="spring.proxy.LogProxy" factory-method="getInstance">
    <constructor-arg ref="UserDao"/>
    </bean>
    </beans>

**LogInfo(annotation):**

@Retention(RetentionPolicy.RUNTIME)
    public @interface LogInfo {
    public String value() default "";
    }

**注意：(1)要加上@Retention(RetentionPolicy.RUNTIME)**

**IUserDao(加入annotation的value):**

public interface IUserDao {
    @LogInfo("add")
    public void add(User user);
    	
    @LogInfo("delete")
    public void delete(int id);
    public User load(int id);
    }

**在service中注入动态dao：**

@Resource(name="UserDynamicDao")
    	public void setUserDao(IUserDao userDao) {
    		UserDao = userDao;
    	}

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