hession client server exception

RPC异常处理概述

RPC异常处理指是，当客户端调用远端的服务，若是服务执行过程当中发生异常，这个异常可否序列到客户端？

若是服务在执行过程当中可能发生异常，那么在服务接口的声明中，就该声明该接口可能抛出的异常。

在Hessian中，服务器端发生异常，能够将异常信息从服务器端序列化到客户端，由于Exception自己是实现了Serializable的，所以，咱们在自定义异常时，不须要显式的让自定义的

异常实现Serializable接口

举例

继续以【RPC框架Hessian二】中的代码为例，修改服务的save方法，刻意的让服务器端的代码抛出异常(抛出的是运行时异常，受检异常与此相似)

package com.tom.hessian.server;

import com.tom.hessian.common.ComplexModel;
import com.tom.hessian.common.IComplexModelService;

import java.util.HashMap;
import java.util.Map;

/**
 * Created by yuzhitao on 14-9-2.
 */
public class ComplexModelService implements IComplexModelService {
  private Map<Integer,ComplexModel> models = new HashMap<Integer, ComplexModel>();
  @Override
  public void save(ComplexModel model) {
    if (model.getId() == null){
      throw new IllegalArgumentException("id could not be null");
    }

    if (model.getId() == 1) { //客户端的model的id为1，所以会发生unchecked exception
      throw new IllegalArgumentException("id could not be 1");
    }

    models.put(model.getId(), model);
  }

  @Override
  public ComplexModel read(Integer modelId) {
    return models.get(modelId);
  }
}

当客户端的model的id为1时，调用save方法，抛出

if (model.getId() == 1) { //客户端的model的id为1，所以会发生unchecked exception
            throw new IllegalArgumentException("id could not be 1");
        }

此时服务器端没有抛出异常，而客户端抛出异常：

Exception in thread "main" java.lang.IllegalArgumentException: id could not be 1
  at com.tom.hessian.server.ComplexModelService.save(ComplexModelService.java:21)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:606)
  at com.caucho.hessian.server.HessianSkeleton.invoke(HessianSkeleton.java:302)
  at com.caucho.hessian.server.HessianSkeleton.invoke(HessianSkeleton.java:198)
  at com.caucho.hessian.server.HessianServlet.invoke(HessianServlet.java:399)
  at com.caucho.hessian.server.HessianServlet.service(HessianServlet.java:379)
  at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
  at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
  at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
  at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
  at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:726)
  at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
  at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:206)
  at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
  at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:139)
  at org.mortbay.jetty.Server.handle(Server.java:324)
  at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
  at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:842)
  at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:648)
  at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
  at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
  at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
  at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:450)

Hessian服务器端异常处理源代码分析

在Hessian的HessianSkeleton类的invoke方法中，经过反射调用服务代码：

try {
      result = method.invoke(service, values); //调用的服务端类、参数和方法
    } catch (Exception e) { //捕获异常
      Throwable e1 = e;
      if (e1 instanceof InvocationTargetException)
        e1 = ((InvocationTargetException) e).getTargetException();

      log.log(Level.FINE, this + " " + e1.toString(), e1);

      out.writeFault("ServiceException", 
        escapeMessage(e1.getMessage()), 
        e1);//将异常信息序列到客户端
      out.close();
      return;
    }