高级Spring之cglib 代理进阶

素颜马尾好姑娘i 2024-03-27 11:06 57阅读 0赞

#### 演示 - 模拟 cglib 代理 ####

代理类准备：

public class Proxy extends Target {
    
        private MethodInterceptor methodInterceptor;
    
        public void setMethodInterceptor(MethodInterceptor methodInterceptor) {
            this.methodInterceptor = methodInterceptor;
        }
    
        static Method save0;
        static Method save1;
        static Method save2;
        static MethodProxy save0Proxy;
        static MethodProxy save1Proxy;
        static MethodProxy save2Proxy;
        static {
            try {
                save0 = Target.class.getMethod("save");
                save1 = Target.class.getMethod("save", int.class);
                save2 = Target.class.getMethod("save", long.class);
                save0Proxy = MethodProxy.create(Target.class, Proxy.class, "()V", "save", "saveSuper");
                save1Proxy = MethodProxy.create(Target.class, Proxy.class, "(I)V", "save", "saveSuper");
                save2Proxy = MethodProxy.create(Target.class, Proxy.class, "(J)V", "save", "saveSuper");
            } catch (NoSuchMethodException e) {
                throw new NoSuchMethodError(e.getMessage());
            }
        }
    
        // >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 带原始功能的方法
        public void saveSuper() {
            super.save();
        }
        public void saveSuper(int i) {
            super.save(i);
        }
        public void saveSuper(long j) {
            super.save(j);
        }
        // >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> 带增强功能的方法
        @Override
        public void save() {
            try {
                methodInterceptor.intercept(this, save0, new Object[0], save0Proxy);
            } catch (Throwable e) {
                throw new UndeclaredThrowableException(e);
            }
        }
    
        @Override
        public void save(int i) {
            try {
                methodInterceptor.intercept(this, save1, new Object[]{i}, save1Proxy);
            } catch (Throwable e) {
                throw new UndeclaredThrowableException(e);
            }
        }
    
        @Override
        public void save(long j) {
            try {
                methodInterceptor.intercept(this, save2, new Object[]{j}, save2Proxy);
            } catch (Throwable e) {
                throw new UndeclaredThrowableException(e);
            }
        }
    }

测试：

public class A14Application {
        public static void main(String[] args) throws InvocationTargetException {
    
            Target target = new Target();
            Proxy proxy = new Proxy();
            
            proxy.setCallbacks(new Callback[]{(MethodInterceptor) (p, m, a, mp) -> {
                System.out.println("proxy before..." + mp.getSignature());
                // ⬇️调用目标方法(三种)
    //            Object result = m.invoke(target, a);  // ⬅️反射调用
    //            Object result = mp.invoke(target, a); // ⬅️非反射调用, 结合目标用
                Object result = mp.invokeSuper(p, a);   // ⬅️非反射调用, 结合代理用
                System.out.println("proxy after..." + mp.getSignature());
                return result;
            }});
            
            // ⬇️调用代理方法
            proxy.save();
        }
    }

> ***注意***
> 
>  *  调用 Object 的方法, 后两种在 jdk >= 9 时都有问题, 需要 --add-opens java.base/java.lang=ALL-UNNAMED

结果：

![bd46f7d2f08b48f5bb865a156bca3bab.png][]

和 jdk 动态代理原理查不多

1.  回调的接口换了一下，InvocationHandler 改成了 MethodInterceptor
2.  调用目标时有所改进，见下面代码片段
    
    1.  method.invoke 是反射调用，必须调用到足够次数才会进行优化
    2.  methodProxy.invoke 是不反射调用，它会正常（间接）调用目标对象的方法（Spring 采用）
    3.  methodProxy.invokeSuper 也是不反射调用，它会正常（间接）调用代理对象的方法，可以省略目标对象

[bd46f7d2f08b48f5bb865a156bca3bab.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/823d459f99e046bc861561e8f33af0dd.png