[Reflect] 4 动态代理

/**
 * @author vincent
 */
public interface UserService {
    void selectById();

    void update();
}

/**
 * @author vincent
 */
public class UserServiceImpl implements UserService {
    @Override
    public void selectById() {
        System.out.println("查询 selectById");
    }

    @Override
    public void update() {
        System.out.println("更新 update");
    }
}

/**
 * @author vincent
 */
public class UserServiceStaticProxy {
    private UserService target;

    public UserServiceStaticProxy(UserService target) {
        this.target = target;
    }

    public void selectById() {
        before();
        // 这里才实际调用真实主题角色的方法
        target.selectById();
        after();
    }

    public void update() {
        before();
        // 这里才实际调用真实主题角色的方法
        target.update();
        after();
    }

    // 在执行方法之前执行
    private void before() {
        System.out.println(String.format("log start time [%s] ", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS").format(new Date())));
    }

    // 在执行方法之后执行
    private void after() {
        System.out.println(String.format("log end time [%s] ", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS").format(new Date())));
    }

}

/**
 * @author vincent
 */
public class ProxyTest {
    @Test
    public void staticTest() {
        UserServiceImpl userServiceImpl = new UserServiceImpl();
        UserServiceStaticProxy proxy = new UserServiceStaticProxy(userServiceImpl);
        proxy.selectById();
        proxy.update();
    }
}

/**
 * @author vincent
 */
public class LogHandler implements InvocationHandler {
    // 被代理的对象，实际的方法执行者
    Object target;

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

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        before();
        Object invoke = method.invoke(target, args);
        after();
        return invoke;
    }

    // 在执行方法之前执行
    private void before() {
        System.out.println(String.format("log start time [%s] ", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS").format(new Date())));
    }

    // 在执行方法之后执行
    private void after() {
        System.out.println(String.format("log end time [%s] ", new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS").format(new Date())));
    }
}

/**
 * 将根据类信息动态生成的二进制字节码保存到硬盘中，默认的是 clazz 目录下
 * params: clazz 需要生成动态代理类的类
 * proxyName: 为动态生成的代理类的名称
 */
public static void generateClassFile(Class clazz, String proxyName) {
    // 根据类信息和提供的代理类名称，生成字节码
    byte[] classFile = ProxyGenerator.generateProxyClass(proxyName, clazz.getInterfaces());
    String paths = clazz.getResource(".").getPath();
    System.out.println(paths);
    FileOutputStream out = null;
    try {
        //保留到硬盘中
        out = new FileOutputStream(paths + proxyName + ".class");
        out.write(classFile);
        out.flush();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

import com.example.reflect.proxy.UserService;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;

public final class UserServiceProxy extends Proxy implements UserService {
    private static Method m1;
    private static Method m2;
    private static Method m4;
    private static Method m0;
    private static Method m3;

    public UserServiceProxy(InvocationHandler var1) throws  {
        super(var1);
    }

    public final boolean equals(Object var1) throws  {
        try {
            return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

    public final String toString() throws  {
        try {
            return (String)super.h.invoke(this, m2, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final void selectById() throws  {
        try {
            super.h.invoke(this, m4, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final int hashCode() throws  {
        try {
            return (Integer)super.h.invoke(this, m0, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final void update() throws  {
        try {
            super.h.invoke(this, m3, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            m2 = Class.forName("java.lang.Object").getMethod("toString");
            m4 = Class.forName("com.example.reflect.proxy.UserService").getMethod("selectById");
            m0 = Class.forName("java.lang.Object").getMethod("hashCode");
            m3 = Class.forName("com.example.reflect.proxy.UserService").getMethod("update");
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
    before();
    Object result = method.invoke(target, args);       // 调用 target 的 method 方法
    after();
    return result;  // 返回方法的执行结果
}

public class UserDao {
    public void select() {
        System.out.println("UserDao 查询 selectById");
    }
    public void update() {
        System.out.println("UserDao 更新 update");
    }
}

import java.lang.reflect.Method;
import java.util.Date;

public class LogInterceptor implements MethodInterceptor {
    /**
     * @param object 表示要进行增强的对象
     * @param method 表示拦截的方法
     * @param objects 数组表示参数列表，基本数据类型需要传入其包装类型，如int-->Integer、long-Long、double-->Double
     * @param methodProxy 表示对方法的代理，invokeSuper方法表示对被代理对象方法的调用
     * @return 执行结果
     * @throws Throwable
     */
    @Override
    public Object intercept(Object object, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        before();
        Object result = methodProxy.invokeSuper(object, objects);   // 注意这里是调用 invokeSuper 而不是 invoke，否则死循环，methodProxy.invokesuper执行的是原始类的方法，method.invoke执行的是子类的方法
        after();
        return result;
    }
    private void before() {
        System.out.println(String.format("log start time [%s] ", new Date()));
    }
    private void after() {
        System.out.println(String.format("log end time [%s] ", new Date()));
    }
}

import net.sf.cglib.proxy.Enhancer;

public class CglibTest {
    public static void main(String[] args) {
        DaoProxy daoProxy = new DaoProxy(); 
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Dao.class);  // 设置超类，cglib是通过继承来实现的
        enhancer.setCallback(daoProxy);

        Dao dao = (Dao)enhancer.create();   // 创建代理类
        dao.update();
        dao.select();
    }
}

public class LogInterceptor2 implements MethodInterceptor {
    @Override
    public Object intercept(Object object, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        before();
        Object result = methodProxy.invokeSuper(object, objects);
        after();
        return result;
    }
    private void before() {
        System.out.println(String.format("log2 start time [%s] ", new Date()));
    }
    private void after() {
        System.out.println(String.format("log2 end time [%s] ", new Date()));
    }
}

// 回调过滤器: 在CGLib回调时可以设置对不同方法执行不同的回调逻辑，或者根本不执行回调。
public class DaoFilter implements CallbackFilter {
    @Override
    public int accept(Method method) {
        if ("select".equals(method.getName())) {
            return 0;   // Callback 列表第1个拦截器
        }
        return 1;   // Callback 列表第2个拦截器，return 2 则为第3个，以此类推
    }
}

public class CglibTest2 {
    public static void main(String[] args) {
        LogInterceptor logInterceptor = new LogInterceptor();
        LogInterceptor2 logInterceptor2 = new LogInterceptor2();
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(UserDao.class);   // 设置超类，cglib是通过继承来实现的
        enhancer.setCallbacks(new Callback[]{logInterceptor, logInterceptor2, NoOp.INSTANCE});   // 设置多个拦截器，NoOp.INSTANCE是一个空拦截器，不做任何处理
        enhancer.setCallbackFilter(new DaoFilter());

        UserDao proxy = (UserDao) enhancer.create();   // 创建代理类
        proxy.select();
        proxy.update();
    }
}