jdk静态代理和jdk动态代理

 局限性:  只能代理某一类型接口的实例,不能代理任意接口任意方法 

             静态代理只能代理固定或单一的方法,也就是说不能做到任何类任何方法的代理 

jdk动态代理灵活性很大,在任何地方都可以使用代理功能,前提是该对象有接口

public class MyHandler implements InvocationHandler {
    
    private Object target;

    public MyHandler() {
    }

    public MyHandler(Object target) {
        this.target = target;
    }

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

    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("=====获取数据连接=====");
        method.invoke(target, args);
        System.out.println("=====关闭连接=====");
        return null;
    }
}

public interface Mapper {
    void jdbcOperator();
}

public class UserMapper implements Mapper {
    public void jdbcOperator(){
        System.out.println("====执行核心业务代码UserMapper====");
    }
}

public static void main(String[] args) {
        UserMapper userMapper = new UserMapper();
        MyHandler myHandler = new MyHandler(userMapper);
        Mapper proxyInstance = 
                   (Mapper) myHandler.getProxyInstance(); //代理对象只能用接口去接
        proxyInstance.jdbcOperator();
//        System.out.println("--------分割线---------");
//        SMapper sMapper = new SMapper();
//        myHandler = new MyHandler(sMapper);
//        AdminMapper mapper = (AdminMapper) myHandler.getProxyInstance();
//        mapper.jdbcOperator();

        TestProxyClass.creatClassFile("$Proxy0", Mapper.class);
    }

public class TestProxyClass {
    public static void creatClassFile(String proxyName,Class clazz) {
        byte[] ClassFile = ProxyGenerator.generateProxyClass(proxyName, new Class[]{clazz});
        String path = "D:\IDEA_Workspace\cgb2107_stage3\proxyapp\target\classes\cn\tedu\util\";
        System.out.println("path"+path);
        FileOutputStream fileOutputStream = null;

        try {
            fileOutputStream = new FileOutputStream(path + proxyName + ".class");
            fileOutputStream.write(ClassFile);
            fileOutputStream.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (fileOutputStream!=null){
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}