引言

我們知道Dubbo消費端引用服務(wù)的時候是根據(jù)本地接口為我們生成代理類,對消費端而言不需要關(guān)心具體的實現(xiàn),代理類幫我們處理底層通信的問題。

        ReferenceConfig<IUserService> reference = newReferenceConfig<IUserService>(); 
        reference.setApplication(application);
        reference.setRegistry(registry); // 多個注冊中心可以用setRegistries()
        reference.setInterface(IUserService.class);
        reference.setVersion("1.0.0");

        //此時的userService只是IUserService的一個代理類
        IUserService userService = reference.get(); 

代理類反編譯

public class Proxy0 extends Proxy implements DC {
    public Object newInstance(InvocationHandler var1) {
        return new proxy0(var1);
    }

    public Proxy0() {
    }
}

package com.alibaba.dubbo.common.bytecode;

import com.alibaba.dubbo.common.bytecode.ClassGenerator.DC;
import com.alibaba.dubbo.demo.service.IUserService;
import com.alibaba.dubbo.rpc.service.EchoService;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.List;

public class proxy0 implements DC, IUserService, EchoService {
    public static Method[] methods;
    private InvocationHandler handler;

    public List findAllUserList() {
        Object[] var1 = new Object[0];
        Object var2 = this.handler.invoke(this, methods[0], var1);
        return (List)var2;
    }

    public String findPasswd(String var1) {
        Object[] var2 = new Object[]{var1};
        Object var3 = this.handler.invoke(this, methods[1], var2);
        return (String)var3;
    }

    public void updateUserById(Integer var1) {
        Object[] var2 = new Object[]{var1};
        this.handler.invoke(this, methods[2], var2);
    }

    public Object $echo(Object var1) {
        Object[] var2 = new Object[]{var1};
        Object var3 = this.handler.invoke(this, methods[3], var2);
        return (Object)var3;
    }

    public proxy0() {
    }

    public proxy0(InvocationHandler var1) {
        this.handler = var1;
    }
}

從代碼中可知,具體的方法都是由handler.invoke()來執(zhí)行的,而且該代理類實現(xiàn)了IUserService接口.我們來看一下JavassistProxyFactory：

public class JavassistProxyFactory extends AbstractProxyFactory {

    @SuppressWarnings("unchecked")
    public <T> T getProxy(Invoker<T> invoker, Class<?>[] interfaces) {
        return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker));
    }

    public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) {
        // TODO Wrapper類不能正確處理帶$的類名
        final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
        return new AbstractProxyInvoker<T>(proxy, type, url) {
            @Override
            protected Object doInvoke(T proxy, String methodName, 
                                      Class<?>[] parameterTypes, 
                                      Object[] arguments) throws Throwable {
                return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
            }
        };
    }
}

從代碼中可知,newInstance()方法里包裝了一個InvokerInvocationHandler()對象仿荆。

public class InvokerInvocationHandler implements InvocationHandler {

    private final Invoker<?> invoker;
    
    public InvokerInvocationHandler(Invoker<?> handler){
        this.invoker = handler;
    }

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        String methodName = method.getName();
        Class<?>[] parameterTypes = method.getParameterTypes();
        if (method.getDeclaringClass() == Object.class) {
            return method.invoke(invoker, args);
        }
        if ("toString".equals(methodName) && parameterTypes.length == 0) {
            return invoker.toString();
        }
        if ("hashCode".equals(methodName) && parameterTypes.length == 0) {
            return invoker.hashCode();
        }
        if ("equals".equals(methodName) && parameterTypes.length == 1) {
            return invoker.equals(args[0]);
        }
        return invoker.invoke(new RpcInvocation(method, args)).recreate();
    }

}

具體的邏輯最終交給了Invoker來執(zhí)行厅贪。