本文记录了一次使用Spring框架进行远程调用时遇到的HessianProtocolException异常的排查过程，通过更改方法名解决了问题，并提出了改进远程服务调用的设计思路。
由于昨天做了一个远程调用架构的项目工程模板demo，虽然大体上可以跑起来了，但有些地方还是有异常。今天决定找出原因。
在办公室的电脑里，我只有spring1.2.9。可能跟之前的spring2.0有点差距，但在spring1.29上也有一点问题。先把这些问题搞定再说。
问题是这样的，登陆的时候老是抛出异常。见如下：
2008
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3
-
24
1
:
48
:
26
org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service()
for
servlet remoting threw exceptioncom.caucho.hessian.io.HessianProtocolException: expected string at z at com.caucho.hessian.io.HessianInput.error(HessianInput.java:
1226
) at com.caucho.hessian.io.HessianInput.expect(HessianInput.java:
1221
) at com.caucho.hessian.io.HessianInput.readString(HessianInput.java:
543
) at com.caucho.hessian.io.BasicDeserializer.readObject(BasicDeserializer.java:
166
) at com.caucho.hessian.io.HessianInput.readObject(HessianInput.java:
699
) at com.caucho.hessian.server.HessianSkeleton.invoke(HessianSkeleton.java:
181
) at org.springframework.remoting.caucho.HessianServiceExporter.handleRequest(HessianServiceExporter.java:
91
) at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:
44
) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:
740
) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:
684
) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:
394
) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:
358
) at javax.servlet.http.HttpServlet.service(HttpServlet.java:
710
) at javax.servlet.http.HttpServlet.service(HttpServlet.java:
803
) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:
290
) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:
206
) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:
230
) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:
175
) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:
128
) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:
104
) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:
109
) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:
261
) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:
844
) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:
581
) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:
447
) at java.lang.Thread.run(Thread.java:
619
)
2008
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3
-
24
1
:
48
:
26
org.apache.catalina.core.StandardWrapperValve invoke严重: Servlet.service()
for
servlet petstore threw exceptioncom.caucho.hessian.io.HessianProtocolException: at com.caucho.hessian.client.HessianProxy.invoke(HessianProxy.java:
171
) at $Proxy0.getAccount(Unknown Source) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:
39
) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:
25
) at java.lang.reflect.Method.invoke(Method.java:
597
) at org.springframework.remoting.caucho.HessianClientInterceptor.invoke(HessianClientInterceptor.java:
115
) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:
169
) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:
169
) at $Proxy1.getAccount(Unknown Source) at org.springframework.samples.jpetstore.web.spring.OrderFormController.formBackingObject(OrderFormController.java:
45
) at org.springframework.web.servlet.mvc.AbstractFormController.getErrorsForNewForm(AbstractFormController.java:
341
) at org.springframework.web.servlet.mvc.AbstractFormController.showNewForm(AbstractFormController.java:
322
) at org.springframework.web.servlet.mvc.AbstractFormController.handleRequestInternal(AbstractFormController.java:
262
) at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:
153
) at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:
44
) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:
740
) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:
684
) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:
394
) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:
348
) at javax.servlet.http.HttpServlet.service(HttpServlet.java:
690
) at javax.servlet.http.HttpServlet.service(HttpServlet.java:
803
) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:
290
) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:
206
) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:
230
) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:
175
) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:
128
) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:
104
) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:
109
) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:
261
) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:
844
) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:
581
) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:
447
) at java.lang.Thread.run(Thread.java:
619
)
百思不得其解！为什么总是执行getAccount(String username, String password)时候抛出异常！？
由于对aop不是很了解，只能是我猜，我猜，我猜猜！是不是代理类出现问题了？再看看源代码，发现方法getAccount被重载了。而且异常信息中有at $Proxy0.getAccount(Unknown Source)。 我想是不是把一个重命名，比如getNewAccount。
一试，果然是这样！
我想，如果存在这样的问题。我们是不是可以参考spring的org.springframework.web.servlet.DispatcherServlet设计，给每个远程业务接口分配一个serviceId，只代理一个叫远程请求分发器的接口RemoteRequestDispatcher，在服务器端RemoteRequestDispatcher的实现类负责根据serviceId将请求转发给相应的类处理。
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