【dubbo源码分析】5. dubbo消费端 - ProxyFactory使用 Invoker创建消费端调用代理类

最新推荐文章于 2022-04-07 22:36:01 发布

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最新推荐文章于 2022-04-07 22:36:01 发布

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分类专栏： java dubbo 文章标签： dubbo consumer 消费端

本文链接：https://blog.youkuaiyun.com/hao495430759/article/details/79927285

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  首先来看看proxyFactory： 

 private static final ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();

  根据 
 Adaptive类/com.alibaba.dubbo.rpc.ProxyFactory 之 Adaptive类  
 文章可知，proxyFactory的Adaptive类主要方法及逻辑如下： 

public class ProxyFactory$Adaptive implements com.alibaba.dubbo.rpc.ProxyFactory {
	public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.RpcException {
  com.alibaba.dubbo.common.URL url = arg0.getUrl();
		String extName = url.getParameter("proxy", "javassist");
		com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
		return extension.getProxy(arg0);
	}
	public com.alibaba.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1, com.alibaba.dubbo.common.URL arg2) throws com.alibaba.dubbo.rpc.RpcException {
		com.alibaba.dubbo.common.URL url = arg2;
		String extName = url.getParameter("proxy", "javassist");
		com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
		return extension.getInvoker(arg0, arg1, arg2);
	}
}

   由此可知， 
  proxyFactory.getProxy(Invoker invoker)  
  最终交由 JavassistProxyFaactory.getProxy(Invoker) 处理，又因为有ProxyFactory 实例包装类  
  StubProxyFactoryWrapper 
  ，因此 
 

 
  ProxyFactory$Adaptive 
  .getProxy(invoker) 方法中  
  com.alibaba.dubbo.rp 
  c.ProxyFactory extension 
   = new  
  StubProxyFactoryWrapper 
  (JavassistProxyFactory); 
 

 
  因此调用链为  
  StubProxyFactoryWrapper 
  .getProxy() ->  
  JavassistProxyFactory 
  .getProxy() -> return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker)) 
  ; 
 

 
  处理流程图如下： 
 

 
  下面看看 
  JavassistProxyFactory 
  .getProxy(Invoker invoker) 
 

 
  这里需要注意的是，生成的consumer代理除了实现指定接口外，还需要实现EchoService(支持回声测深，用于检查服务是否可用）。接下来就是真正的代理类生成了 
 

 
  我们看Proxy.getProxy(interfaces)方法： 
 

public static Proxy getProxy(Class<?>... ics) {
        return getProxy(ClassHelper.getClassLoader(Proxy.class), ics);
  }
  public static Proxy getProxy(ClassLoader cl, Class<?>... ics) {
........
//关键代码
String pkg = null;
        ClassGenerator ccp = null, ccm = null;
        try {
            ccp = ClassGenerator.newInstance(cl);

            Set<String> worked = new HashSet<String>();
            List<Method> methods = new ArrayList<Method>();

            for (int i = 0; i < ics.length; i++) {
                if (!Modifier.isPublic(ics[i].getModifiers())) {
                    String npkg = ics[i].getPackage().getName();
                    if (pkg == null) {
                        pkg = npkg;
                    } else {
                        if (!pkg.equals(npkg))
                            throw new IllegalArgumentException("non-public interfaces from different packages");
                    }
                }
                ccp.addInterface(ics[i]); //此处循环将方法传入的interfaces添加 （即实现所有传入的接口 implements Interface1,interface2）

                for (Method method : ics[i].getMethods()) {
                    String desc = ReflectUtils.getDesc(method);
                    if (worked.contains(desc))
                        continue;
                    worked.add(desc);

                    int ix = methods.size();
                    Class<?> rt = method.getReturnType();
                    Class<?>[] pts = method.getParameterTypes();

                    StringBuilder code = new StringBuilder("Object[] args = new Object[").append(pts.length).append("];");
                    for (int j = 0; j < pts.length; j++)
                        code.append(" args[").append(j).append("] = ($w)$").append(j + 1).append(";");
                    code.append(" Object ret = handler.invoke(this, methods[" + ix + "], args);");
                    if (!Void.TYPE.equals(rt))
                        code.append(" return ").append(asArgument(rt, "ret")).append(";");

                    methods.add(method);
                    ccp.addMethod(method.getName(), method.getModifiers(), rt, pts, method.getExceptionTypes(), code.toString());  //此处将传入的接口里所有接口方法进行实现(即 @override)
                }
            }

            if (pkg == null)
                pkg = PACKAGE_NAME;

            // create ProxyInstance class.  开始生成consumer接口代理类（生成的代码逻辑见代码1）
            String pcn = pkg + ".proxy" + id;
            ccp.setClassName(pcn);
            ccp.addField("public static java.lang.reflect.Method[] methods;");
            ccp.addField("private " + InvocationHandler.class.getName() + " handler;");
            ccp.addConstructor(Modifier.PUBLIC, new Class<?>[]{InvocationHandler.class}, new Class<?>[0], "handler=$1;");
            ccp.addDefaultConstructor();
            Class<?> clazz = ccp.toClass();
            clazz.getField("methods").set(null, methods.toArray(new Method[0]));

            // create Proxy class.  此处代码逻辑开始生成 抽象类 Proxy  的实现类（代码见 代码2）
            String fcn = Proxy.class.getName() + id;
            ccm = ClassGenerator.newInstance(cl);
            ccm.setClassName(fcn);
            ccm.addDefaultConstructor();
            ccm.setSuperClass(Proxy.class);
            ccm.addMethod("public Object newInstance(" + InvocationHandler.class.getName() + " h){ return new " + pcn + "($1); }");
            Class<?> pc = ccm.toClass();
            proxy = (Proxy) pc.newInstance();
        } catch (RuntimeException e) {
            throw e;
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage(), e);
        } finally {
            // release ClassGenerator
            if (ccp != null)
                ccp.release();
            if (ccm != null)
                ccm.release();
            synchronized (cache) {
                if (proxy == null)
                    cache.remove(key);
                else
                    cache.put(key, new WeakReference<Proxy>(proxy));
                cache.notifyAll();
            }
        }
        return proxy;
｝

最终生成的消费端服务代理类（代码1 ）如下：

package com.alibaba.dubbo.common.bytecode;

import com.alibaba.dubbo.demo.DemoService;
import com.alibaba.dubbo.rpc.service.EchoService;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

// 见com.alibaba.dubbo.common.bytecode.Proxy.getProxy
public class proxy0 implements ClassGenerator.DC, EchoService, DemoService {
  // methods包含proxy0实现的所有接口方法（去重）
  public static Method[] methods;   //methods = {syaHello,$echo}
  private InvocationHandler handler;

  public String sayHello(String arg0) {
    Object[] args = new Object[1];
    args[0] = arg0;
    Object localObject = this.handler.invoke(this, methods[0], args);
    return (String)localObject;
  }

  public Object $echo(Object arg0) {
    Object[] args = new Object[1];
    args[0] = arg0;
    Object localObject = this.handler.invoke(this, methods[1], args);
    return (Object)localObject;
  }

  public proxy0() {
  }

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

和抽象类Proxy的子类（代码2 ）：

com.alibaba.dubbo.common.bytecode.Proxy0 extends Proxy {
public Proxy0(){
}
	
public Object newInstance(java.lang.reflect.InvocationHandler h){ 
		return new com.alibaba.dubbo.common.bytecode.proxy0($1);  //$1 即为方法入参1
	}
}

因此

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

   首先 
  Proxy.getProxy(interfaces) 会先返回抽象类 
  Proxy的 实现类 Proxy0 （ 
  见代码2 
  ）；接着调用 
  newInstance(InvokerInvocationHandler handler) 
 

   返回consumer服务代理类 
  new com.alibaba.dubbo.common.bytecode.proxy0( 
  new InvokerInvocationHandler(invoker) 
  )  
 

   因此最终返回至 StubProxyFactoryWrapper 的 T proxy = proxyFactory.getProxy(invoker); 为 
  new com.alibaba.dubbo.common.bytecode.proxy0( 
  new InvokerInvocationHandler(invoker) 
  ) ; 
 

 
  proxy0 包含了DemoService服务接口的方法实现（ 
  见代码1）

   下面来看StubProxyFactoryWrapper 在获取到 consumer服务代理后进行哪些改造： 
 

public <T> T getProxy(Invoker<T> invoker) throws RpcException {
        T proxy = proxyFactory.getProxy(invoker);//获取consumer服务代理类
        if (GenericService.class != invoker.getInterface()) {
            String stub = invoker.getUrl().getParameter(Constants.STUB_KEY, invoker.getUrl().getParameter(Constants.LOCAL_KEY)); //url中设置了 stub参数
            if (ConfigUtils.isNotEmpty(stub)) {
                Class<?> serviceType = invoker.getInterface();
                if (ConfigUtils.isDefault(stub)) {
                    if (invoker.getUrl().hasParameter(Constants.STUB_KEY)) {  //设置了stub则构造  interfaceStub 
                        stub = serviceType.getName() + "Stub";
                    } else {
                        stub = serviceType.getName() + "Local";   //否则构造 interfeceLocal
                    }
                }
                try {
                    Class<?> stubClass = ReflectUtils.forName(stub);   //生成Stub的Class
                    if (!serviceType.isAssignableFrom(stubClass)) {
                        throw new IllegalStateException("The stub implementation class " + stubClass.getName() + " not implement interface " + serviceType.getName());
                    }
                    try {
                        Constructor<?> constructor = ReflectUtils.findConstructor(stubClass, serviceType);  //构建Stub instance
                        proxy = (T) constructor.newInstance(new Object[]{proxy});
                        //export stub service
                        URL url = invoker.getUrl();
                        if (url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT)) {
                            url = url.addParameter(Constants.STUB_EVENT_METHODS_KEY, StringUtils.join(Wrapper.getWrapper(proxy.getClass()).getDeclaredMethodNames(), ","));
                            url = url.addParameter(Constants.IS_SERVER_KEY, Boolean.FALSE.toString());
                            try {
                                export(proxy, (Class) invoker.getInterface(), url);
                            } catch (Exception e) {
                                LOGGER.error("export a stub service error.", e);
                            }
                        }
                    } catch (NoSuchMethodException e) {
                        throw new IllegalStateException("No such constructor \"public " + stubClass.getSimpleName() + "(" + serviceType.getName() + ")\" in stub implementation class " + stubClass.getName(), e);
                    }
                } catch (Throwable t) {
                    LOGGER.error("Failed to create stub implementation class " + stub + " in consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", cause: " + t.getMessage(), t);
                    // ignore
                }
            }
        }
        return proxy;
    }

    public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) throws RpcException {
        return proxyFactory.getInvoker(proxy, type, url);
    }

    private <T> Exporter<T> export(T instance, Class<T> type, URL url) {
        return protocol.export(proxyFactory.getInvoker(instance, type, url));
    }

   以上分析得出，最终返回至ReferenceConfig 的 ref=createProxy(map) -> return proxyFactory.getProxy(Invoker); 即为 
  new com.alibaba.dubbo.common.bytecode.proxy0( 
  new InvokerInvocationHandler(invoker) 
  ) 
 

   DemoService 引用构建完毕 
 