一、接口定义

定义接口

public interface IUserApi {
    String queryUserInfo();
}

实现接口

public class UserApi implements IUserApi {
    public String queryUserInfo() {
        return "查询用户信息！";
    }
}

二、JDK代理方式

public class JDKProxy {
    public static <T> T getProxy(Class clazz) throws Exception {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        return (T) Proxy.newProxyInstance(classLoader, new Class[]{clazz}, new InvocationHandler() {
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                System.out.println(method.getName() + " 你被代理了，By JDKProxy！");
                return "查询用户信息！";
            }
        });
    }
}
@Test
public void test_JDKProxy() throws Exception {
    IUserApi userApi = JDKProxy.getProxy(IUserApi.class);
    String invoke = userApi.queryUserInfo();
    logger.info("测试结果：{}", invoke);
}

三、 CGLIB代理方式

public class CglibProxy implements MethodInterceptor {
    public Object newInstall(Object object) {
        return Enhancer.create(object.getClass(), this);
    }
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("我被CglibProxy代理了");
        return methodProxy.invokeSuper(o, objects);
    }
}
@Test
public void test_CglibProxy() throws Exception {
    CglibProxy cglibProxy = new CglibProxy();
    UserApi userApi = (UserApi) cglibProxy.newInstall(new UserApi());
    String invoke = userApi.queryUserInfo();
    logger.info("测试结果：{}", invoke);
}

四、ASM代理方式

public class ASMProxy extends ClassLoader {
    public static <T> T getProxy(Class clazz) throws Exception {
        ClassReader classReader = new ClassReader(clazz.getName());
        ClassWriter classWriter = new ClassWriter(classReader, ClassWriter.COMPUTE_MAXS);
        classReader.accept(new ClassVisitor(ASM5, classWriter) {
            @Override
            public MethodVisitor visitMethod(int access, final String name, String descriptor, String signature, String[] exceptions) {
                // 方法过滤
                if (!"queryUserInfo".equals(name))
                    return super.visitMethod(access, name, descriptor, signature, exceptions);
                final MethodVisitor methodVisitor = super.visitMethod(access, name, descriptor, signature, exceptions);
                return new AdviceAdapter(ASM5, methodVisitor, access, name, descriptor) {
                    @Override
                    protected void onMethodEnter() {
                        // 执行指令；获取静态属性
                        methodVisitor.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
                        // 加载常量 load constant
                        methodVisitor.visitLdcInsn(name + " 你被代理了，By ASM！");
                        // 调用方法
                        methodVisitor.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
                        super.onMethodEnter();
                    }
                };
            }
        }, ClassReader.EXPAND_FRAMES);
        byte[] bytes = classWriter.toByteArray();
        return (T) new ASMProxy().defineClass(clazz.getName(), bytes, 0, bytes.length).newInstance();
    }
}
@Test
public void test_ASMProxy() throws Exception {
    IUserApi userApi = ASMProxy.getProxy(UserApi.class);
    String invoke = userApi.queryUserInfo();
    logger.info("测试结果：{}", invoke);
}

五、Byte-Buddy代理方式

public class ByteBuddyProxy {
    public static <T> T getProxy(Class clazz) throws Exception {
        DynamicType.Unloaded<?> dynamicType = new ByteBuddy()
                .subclass(clazz)
                .method(ElementMatchers.<MethodDescription>named("queryUserInfo"))
                .intercept(MethodDelegation.to(InvocationHandler.class))
                .make();
        return (T) dynamicType.load(Thread.currentThread().getContextClassLoader()).getLoaded().newInstance();
    }
}
@RuntimeType
public static Object intercept(@Origin Method method, @AllArguments Object[] args, @SuperCall Callable<?> callable) throws Exception {
    System.out.println(method.getName() + " 你被代理了，By Byte-Buddy！");
    return callable.call();
}
@Test
public void test_ByteBuddyProxy() throws Exception {
    IUserApi userApi = ByteBuddyProxy.getProxy(UserApi.class);
    String invoke = userApi.queryUserInfo();
    logger.info("测试结果：{}", invoke);
}

六、Javassist代理方式

public class JavassistProxy extends ClassLoader {
    public static <T> T getProxy(Class clazz) throws Exception {
        ClassPool pool = ClassPool.getDefault();
        // 获取类
        CtClass ctClass = pool.get(clazz.getName());
        // 获取方法
        CtMethod ctMethod = ctClass.getDeclaredMethod("queryUserInfo");
        // 方法前加强
        ctMethod.insertBefore("{System.out.println(\"" + ctMethod.getName() + " 你被代理了，By Javassist\");}");
        byte[] bytes = ctClass.toBytecode();
        return (T) new JavassistProxy().defineClass(clazz.getName(), bytes, 0, bytes.length).newInstance();
    }
}
@Test
public void test_JavassistProxy() throws Exception {
    IUserApi userApi = JavassistProxy.getProxy(UserApi.class)
    String invoke = userApi.queryUserInfo();
    logger.info("测试结果：{}", invoke);
}