Spring学习(二) AOP 面向切面编程之代理(二)

Aop的实现提供了两种代理:

1. JDK动态代理
2. CGLIb动态代理

　　JDK动态代理:只能为接口创建代理实例

　　CGLib动态代理:一个创建处理器能为所有的类创建代理实例.

　　CGLIB实现原理:是因为CGLIB采用底层的字节码技术,可以为类创建一个子类,在子类中采用方法拦截的技术,拦截所有父类方法的调用,再顺势织入横切逻辑.

　　1.JDK实现动态代理

public interface ForumService {
	
	public int remove(int id);
	
	public void removeAll();
}

　　

public class ForumServiceImpl  implements ForumService{

	@Override
	public int remove(int id) {
		System.out.println(id+"删除成功");
		return id;
	}
	
	public void removeAll() {
		throw new RuntimeException("运行异常");
	}
}

　　

/**
 * 性能监听
 * @author Administrator
 *
 */
public class MethodPerformace {
	private long begin;
	private long end;
	private String serviceMethod;
	public MethodPerformace(String serviceMethod) {
		super();
		this.serviceMethod = serviceMethod;
		this.begin=System.currentTimeMillis();
	}
	
	public  void  printPerformace() {
		end=System.currentTimeMillis();
		long elapse=end-begin;
		System.out.println(serviceMethod+"花费了"+elapse+"多少秒");
	}
	
	

}

　　

public class PerformanceHandler implements InvocationHandler{

	private Object target;
	
	/**
	 * proxy 是最终生成的代理模式
	 * method 是被代理目标实例的某个具体方法,通过它可以发起目标实例方法的反射调用
	 * args 是被代理实例某个方法的入参,在方法反射调用时使用
	 */
	@Override
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		PerformanceMonitor.begin(target.getClass().getName()+"."+method.getName());
		Object obj = method.invoke(target, args);
		PerformanceMonitor.end();
		return obj;
	}

	public PerformanceHandler(Object target) {
		super();
		this.target = target;
	}

}

　　

/**
 * 性能监视器
 * @author Administrator
 *
 */
public class PerformanceMonitor {
		
	//通过一个ThreadLocal保存与调用线程相关的性能监视信息
	private static ThreadLocal<MethodPerformace> local=new ThreadLocal<MethodPerformace>();
	
	//启动对某一目标方法的性能监测
	public static void begin(String method) {
		System.out.println("begin monitor...");
		MethodPerformace performace=new MethodPerformace(method);
		local.set(performace);
	}
	
	public static void end() {
		System.out.println("end monitor...");
		MethodPerformace mp = local.get();
		mp.printPerformace();
	}
	
	
}

　　

public class FourmServiceTest {
	@Test
	public void proxy() {
		ForumService target = new ForumServiceImpl(); // 目标业务类
		PerformanceHandler handler = new PerformanceHandler(target);
		ForumService proxy = (ForumService) Proxy.newProxyInstance(target.getClass().getClassLoader(),
				target.getClass().getInterfaces(), handler);
		proxy.remove(0);
	}
	
}

　2.CGLib实现动态代理

public class CGLibProxy implements MethodInterceptor{
	private Enhancer enhancer=new Enhancer();
	
	public Object getProxy(Class  clazz) {
		enhancer.setSuperclass(clazz);
		enhancer.setCallback(this);
		return enhancer.create();
	}

	@Override
	public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
		PerformanceMonitor.begin(obj.getClass().getName()+"."+method.getName());
		Object result = proxy.invokeSuper(obj, args);
		PerformanceMonitor.end();
		return result;
	}

	
}

　　

public class FourmServiceTest {
	@Test
	public void cgLibProxy() {
		CGLibProxy proxy=new CGLibProxy();
		ForumService forumService=(ForumServiceImpl)proxy.getProxy(ForumServiceImpl.class);
		forumService.remove(0);
	}

}