AOP的最简单的两种实现方式

这里介绍下aop最简单的两种实现方式。
1、动态代理
2、cglib
首先看动态代理。
动态代理大家都知道是必须基于接口的实现
1、接口

import com.xxx.aop.User;

public interface IUserbean {

	public void addUser(User user);

	public User getUser(int id);

}

2、要代理的类

import com.xxx.aop.User;

public class UserbeanImpl implements IUserbean {

	public void addUser(User user) {
		System.out.println("Add user");
	}

	public User getUser(int id) {
		User u = new User();
		u.setName("li1");
		return u;
	}

}

3、代理类

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import com.xxx.aop.User;

public class JDKProxy implements InvocationHandler {

	private Object target;

	public Object bind(Object target) {
		this.target = target;
		return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);

	}

	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		if (method.getName().equals("getUser")) {
			before((Integer) args[0]);
		} else {
			before(args);
		}
		Object result = null;
		result = method.invoke(target, args);
		if (method.getName().equals("getUser")) {
			afert((User) result);
		} else {
			afert(result);
		}

		return result;
	}

	private void afert(Object o) {
		System.out.println(o);
	}

	private void before(int id) {
		System.out.println(id);
	}

	private void before(Object[] args) {
		System.out.println(((User) args[0]).getName());
	}

	private void afert(User user) {
		System.out.println(user.getName());
	}

}

其中还添加了4个afert 与 before方法。Spring aop就是通过配置文件来完全实现的。下章我们也会通过配置文件来实现。
4、测试类

import com.xxx.aop.User;

public class TestProxy {

	public static void main(String[] args) {
		JDKProxy proxy = new JDKProxy();
		IUserbean userBean = (IUserbean) proxy.bind(new UserbeanImpl());
		User user = new User();
		user.setId(1);
		user.setName("li");
		userBean.addUser(user);
		userBean.getUser(1);
	}

}

5、User javebean类

public class User {

	private int id;

	private String name;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

}

cglib原理完全一样，只是实现的不一样

1、被代理的类

import com.xxx.aop.User;

public class UserBean {

	public UserBean() {
	}

	public void addUser(User user) {
		System.out.println("this is addUser() method!");
	}

	public void deleteUser() {
		System.out.println("this is deleteUser() method!");
	}

	public void getUser(User user) {
		throw new NullPointerException("It is null");
	}

	public void updateUser() {
		System.out.println("this is updateUser() method!");
	}

}

2、代理类

public class CGLibProxy implements MethodInterceptor {

	private Object targetObject;

	public Object createProxyObject(Object targetObject) {
		this.targetObject = targetObject;
		Enhancer enhancer = new Enhancer();
		enhancer.setSuperclass(this.targetObject.getClass());
		enhancer.setCallback(this);
		return enhancer.create();
	}

	public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
		before(args);
		Object result = null;
		try {
			result = methodProxy.invoke(targetObject, args);
		} catch (Exception e) {
			System.out.println(e.getMessage());
		}
		afert(args);
		return result;
	}

	private void before(Object[] args) {
		System.out.println(((User) args[0]).getName());
	}

	private void afert(Object[] args) {
		System.out.println(((User) args[0]).getName());
	}
}

3、测试类

import com.xxx.aop.User;

public class TestProxy {

	public static void main(String[] args) {
		CGLibProxy cProxy = new CGLibProxy();
		UserBean userBean = (UserBean) cProxy.createProxyObject(new UserBean());
		User user = new User();
		user.setId(1);
		user.setName("li");
		userBean.addUser(user);
		userBean.getUser(user);
	}
}

通过以上就可以看出通过代理，我们可以获取被代理类的方法，类名，参数以及返回值。