反编译 Dubbo 中的 JDK 动态代理类

反编译的目的：主要是在调用dubbo时，debug 跟进去后发现调用InvokerInvocationHandler.invoke() 方法，稍带有些疑惑，所以进行了代理类的class 流进行输出并反编译。

在 dubbo-demo-consumer中，做如下更改，将动态代理类写入磁盘中，然后反编译观察，加深对动态代理的理解。

public class ProxyGeneratorUtils {
    /**
     * 把代理类的字节码写到硬盘上
     *
     * @param path 保存路径
     */
    public static void writeProxyClassToHardDisk(String path) {
        // 获取代理类的字节码
        byte[] classFile = ProxyGenerator.generateProxyClass("$Proxy11", new Class[]{DemoService.class});

        FileOutputStream out = null;

        try {
            out = new FileOutputStream(path);
            out.write(classFile);
            out.flush();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

上述ProxyGeneratorUtils类使用

对Consumer添加一行代码，如下：

public class Consumer {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"META-INF/spring/dubbo-demo-consumer.xml"});
        context.start();

        DemoService demoService = (DemoService) context.getBean("demoService"); // 获取远程服务代理

        // 输出 class 字节到文件
        ProxyGeneratorUtils.writeProxyClassToHardDisk("f://Proxy$Consumer.class");

        String hello = demoService.sayHello("world"); // 执行远程方法

        System.out.println(hello); // 显示调用结果
    }
}

进入上述文件输出磁盘F ，反编译改文件

import com.alibaba.dubbo.demo.*;
import java.lang.reflect.*;
public final class $Proxy11 extends Proxy implements DemoService
{
    private static Method m1;
    private static Method m3;
    private static Method m2;
    private static Method m0;
    
    public $Proxy11(final InvocationHandler invocationHandler) {
        super(invocationHandler);
    }
    
    public final boolean equals(final Object o) {
        try {
            return (boolean)super.h.invoke(this, $Proxy11.m1, new Object[] { o });
        }
        catch (Error | RuntimeException error) {
            throw;
        }
        catch (Throwable t) {
            throw new UndeclaredThrowableException(t);
        }
    }
    
    public final String sayHello(final String s) {
        try {
            return (String)super.h.invoke(this, $Proxy11.m3, new Object[] { s });
        }
        catch (Error | RuntimeException error) {
            throw;
        }
        catch (Throwable t) {
            throw new UndeclaredThrowableException(t);
        }
    }
    
    public final String toString() {
        try {
            return (String)super.h.invoke(this, $Proxy11.m2, null);
        }
        catch (Error | RuntimeException error) {
            throw;
        }
        catch (Throwable t) {
            throw new UndeclaredThrowableException(t);
        }
    }
    
    public final int hashCode() {
        try {
            return (int)super.h.invoke(this, $Proxy11.m0, null);
        }
        catch (Error | RuntimeException error) {
            throw;
        }
        catch (Throwable t) {
            throw new UndeclaredThrowableException(t);
        }
    }
    
    static {
        try {
            $Proxy11.m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            $Proxy11.m3 = Class.forName("com.alibaba.dubbo.demo.DemoService").getMethod("sayHello", Class.forName("java.lang.String"));
            $Proxy11.m2 = Class.forName("java.lang.Object").getMethod("toString", (Class[])new Class[0]);
            $Proxy11.m0 = Class.forName("java.lang.Object").getMethod("hashCode", (Class[])new Class[0]);
        }
        catch (NoSuchMethodException ex) {
            throw new NoSuchMethodError(ex.getMessage());
        }
        catch (ClassNotFoundException ex2) {
            throw new NoClassDefFoundError(ex2.getMessage());
        }
    }
}

至此可以观察到 sayHello 方法的调用实现逻辑。

转载于:https://www.cnblogs.com/kakacbing/p/8991076.html