需求：使用AOP方式打印日志

用户service层,接口与实现类

public interface IUserService {
    void addUser(String name);
}

public class UserService implements IUserService{

    @Override
    public void addUser(String name) {
        System.out.println("将"+name+"添加到数据库");
    }
    
}

1.静态代理

静态代理，使用一个代理类，需要实现服务的接口，来代理用户的动作，并添加一些另外的东西

public class StaticProxy implements IUserService{

    private IUserService userservice = new UserService();
    
    @Override
    public void addUser(String name) {
        
        userservice.addUser(name);
        System.out.println("我是日志：添加了"+name);
        
    }
    
}

效果如下

image.png

2.动态代理

jdk动态代理

jdk动态代理有个前提，就是被代理的类必须要实现接口

还是上面的两个

public class JDKProxy implements InvocationHandler{

    private Object object;
    
    public Object createProxyInstance(Object object) {
        this.object = object;
        return Proxy.newProxyInstance(object.getClass().getClassLoader()
                , object.getClass().getInterfaces(), this);
    }
    
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        //执行额外的逻辑
        System.out.println("我是日志，前置处理");
        //执行原来的逻辑
        Object invoke = method.invoke(object,args);
        return invoke;
    }
    
}

测试用例

@Test
    public void testJdkProxy() {
        
        IUserService userService = new UserService();
        
        JDKProxy jdkProxy = new JDKProxy();
        IUserService createProxyInstance = (IUserService)jdkProxy.createProxyInstance(userService);
        createProxyInstance.addUser("李四");
        
    }

效果如下

image.png

cglib动态代理

因为jdk代理需要被代理类实现接口，没必要为每个类都实现接口，所以就出现了cglib

public class Admin {

    public void addAdmin(String name) {
        System.out.println("添加了"+name);
    }
    
}

cglib代理类

public class CglibProxy implements MethodInterceptor{

    private Enhancer enhancer = new Enhancer();
    
    public Object getProxyInstance(Class clazz){
        enhancer.setSuperclass(clazz);
        enhancer.setCallback(this);
        return enhancer.create();
    }
    
    
    
    @Override
    public Object intercept(Object object, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("我是日志：是前置处理");
        //通过代理子类来调用父类的方法
        Object invoke = proxy.invokeSuper(object, args);
        System.out.println(args.toString());
        return invoke;
    }
    
}

测试用例

@Test
    public void testCglibProxy() {
        CglibProxy cglibProxy = new CglibProxy();
        IUserService proxyInstance = (IUserService)cglibProxy.getProxyInstance(UserService.class);
        proxyInstance.addUser("王五");
        
    }

效果如下

image.png

代码请到码云下载：https://gitee.com/zhangqiye/java-proxy

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