Java JDK动态代理在拦截器和声明式接口中的应用小结

public interface Performer {
    void play(String subject);
    String introduction();
}
public interface Director {
    List<String> getCreations();
}
public class DefaultActor implements Performer {
    @Override
    public void play(String subject) {
        System.out.println("[DefaultActor]: 默认男演员正在即兴表演《" + subject + "》");
    }
    @Override
    public String introduction() {
        return "李白·上李邕： 大鹏一日同风起，扶摇直上九万里。假令风歇时下来，犹能颠却沧溟水。世人见我恒殊调，闻余大言皆冷笑。宣父尚能畏后生，丈夫未可轻年少。";
    }
}
public class DefaultDirector implements Director {
    @Override
    public List<String> getCreations() {
        List<String> creations = new ArrayList<>();
        creations.add("《霸王别姬》");
        creations.add("《活着》");
        return creations;
    }
}

package guzb.diy.proxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class ProxyForInterceptor implements InvocationHandler {
    private Object target;
    public ProxyForInterceptor(Object target) {
        this.target = target;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("前置拦截逻辑：开始执行 " + method.getName() + " 方法");
        Object result = method.invoke(target, args);
        System.out.println("后置拦截逻辑：完成执行 " + method.getName() + " 方法");
        return result;
    }
}

public class IntercepterTestMain {
    public static void main(String[] args) {
        // 创建原始对象
        Performer actor = new DefaultActor();
        Director director = new DefaultDirector();
        // 创建代理对象
        Performer actorProxy = (Performer) Proxy.newProxyInstance(
                Performer.class.getClassLoader(),
                new Class[]{Performer.class},
                new ProxyForInterceptor(actor)
        );
        Director directorProxy = (Director) Proxy.newProxyInstance(
                Director.class.getClassLoader(),
                new Class[]{Director.class},
                new ProxyForInterceptor(director)
        );
        // 通过代理对象调用方法
        actorProxy.play("京剧");
        System.out.println(actorProxy.introduction());
        System.out.println("导演的作品集：");
        directorProxy.getCreations().forEach(System.out::println);
    }
}

public interface UserMapper {
    @Select("SELECT * FROM user WHERE name = #{name}")
    User findUserByName(String name);
}
// User的POJO类
class User {
    private Integer id;
    private String name;
    // getters and setters
}

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class MyBatisInvocationHandler implements InvocationHandler {
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        // 这里假设能够获取到注解并解析它
        // 实际上，你需要一个SQL执行器来执行这里定义的SQL
        System.out.println("Executing method: " + method.getName());
        System.out.println("Parameters: " + Arrays.toString(args));
        // 模拟的SQL执行结果
        User user = new User();
        user.setId(1);
        user.setName((String) args[0]);
        return user;
    }
}

import java.lang.reflect.Proxy;
public class MyBatisProxyDemo {
    public static void main(String[] args) {
        MyBatisInvocationHandler handler = new MyBatisInvocationHandler();
        UserMapper mapper = (UserMapper) Proxy.newProxyInstance(
            UserMapper.class.getClassLoader(),
            new Class[]{UserMapper.class},
            handler
        );
        User user = mapper.findUserByName("Alice");
        System.out.println("Found user: " + user.getName());
    }
}