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List:       esb-java-dev
Subject:    Re: [esb-java-dev] Re: Feedback Hessian-Support in SNAPSHOT-Build
From:       Ruwan Linton <ruwan () wso2 ! com>
Date:       2008-03-31 10:52:41
Message-ID: 47F0BFA9.6050407 () wso2 ! com
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Hi Eric,
>
> good question. Here is what the Hessian client basically does (somewhere
> in HessianProxy.invoke...)
>
>
>     try {
>       if (! _factory.isOverloadEnabled()) {
>       }
>       else if (args != null)
>         methodName = methodName + "__" + args.length;
>       else
>         methodName = methodName + "__0";
>
>       conn = sendRequest(methodName, args);
>
>       if (conn instanceof HttpURLConnection) {
> 	httpConn = (HttpURLConnection) conn;
>         int code = 500;
>
>         try {
>           code = httpConn.getResponseCode();
>         } catch (Exception e) {
>         }
>
>         if (code != 200) {
>           StringBuffer sb = new StringBuffer();
>           int ch;
>
>           try {
>             is = httpConn.getInputStream();
>
>             if (is != null) {
>               while ((ch = is.read()) >= 0)
>                 sb.append((char) ch);
>
>               is.close();
>             }
>
>             is = httpConn.getErrorStream();
>             if (is != null) {
>               while ((ch = is.read()) >= 0)
>                 sb.append((char) ch);
>             }
>           } catch (FileNotFoundException e) {
>             throw new HessianRuntimeException(String.valueOf(e));
>           } catch (IOException e) {
> 	    if (is == null)
> 	      throw new HessianProtocolException(code + ": " + e, e);
>           }
>
>           if (is != null)
>             is.close();
>
>           throw new HessianProtocolException(code + ": " +
> sb.toString());
>         }
>       }
>
>       is = conn.getInputStream();
>
>       AbstractHessianInput in = _factory.getHessianInput(is);
>
>       return in.readReply(method.getReturnType());
>     } catch (HessianProtocolException e) {
>       throw new HessianRuntimeException(e);
>     } finally {
>       try {
> 	if (is != null)
> 	  is.close();
>       } catch (Throwable e) {
>       }
>       
>       try {
> 	if (httpConn != null)
> 	  httpConn.disconnect();
>       } catch (Throwable e) {
>       }
>     }
>
>
> So if I understand the code correctly, you are right about your
> assumption. Though the code is capable to handle HTTP 500 and extract
> it's error details, normal hessian faults should be received via HTTP
> 200.
>   
Yes, exactly.
> Then the HessianInput.readReply should take care of errors as described
> in the spec. 
>
> Here is the respective code:
>
> public Object readReply(Class expectedClass)
>     throws Throwable
>   {
>     int tag = read();
>     
>     if (tag != 'r')
>       error("expected hessian reply");
>
>     int major = read();
>     int minor = read();
>
>     tag = read();
>     if (tag == 'f')
>       throw prepareFault();
>     else {
>       _peek = tag;
>     
>       Object value = readObject(expectedClass);
>       
>       completeValueReply();
>       
>       return value;
>     }
>   }
>
>   private Throwable prepareFault()
>     throws IOException
>   {
>     HashMap fault = readFault();
>
>     Object detail = fault.get("detail");
>     String message = (String) fault.get("message");
>
>     if (detail instanceof Throwable) {
>       _replyFault = (Throwable) detail;
>       
>       if (message != null && _detailMessageField != null) {
> 	try {
> 	  _detailMessageField.set(_replyFault, message);
> 	} catch (Throwable e) {
> 	}
>       }
> 	
>       return _replyFault;
>     }
>
>     else {
>       String code = (String) fault.get("code");
>         
>       _replyFault = new HessianServiceException(message, code, detail);
>
>       return _replyFault;
>     }
>   }
>
> So now I have a few basic questions in mind (brainstorming):
>
> a) Should WSO ESB try to handle HTTP 500 of content type text/html
> correctly (try to extract error message)?
>   
We can do this, I am in the process of getting a sample to work with 
HTML 500 responses.
> I have to contact our developers and ask them why we use our own version
> of HessianProxy called JHessianProxy. There I found the following
> handling of http status:
>
> if (code != HttpStatus.SC_OK) {
>     throw new HessianRuntimeException(
>         postMethod.getStatusLine().toString());
> }
>
> They used the Apache HTTPClient to send the Hessian requests.
>
>
> b) Is it correct that an HTTP 500 response of content type txt/html is
> send if an IOException is raised within the service method?
>
> Acording to the servlet spec HTTP 500 seems to be correct. I could not
> find much about the content type problem.
>   
I think here the problem is Servlet container is the one who receives 
the IOExceptions, so the servlet engine posts a HTTP 500 with text/html 
content.
> c) Is it correct to throw a subclass of IOException if the Hessian
> implementations wants to signal a protocol violation?
>
> I don't think so. But I don't think that counts as you can't control
> what somebody might throw within a servlets service method.
>   
Well, I don't know the exact answer for this? May be you can ask this 
from the hessian list?
>> BTW: I found the root cause for the blocking behavior and fixed it,
>> still ESB cannot handle the HTML fault for the Hessian requests, but
>>     
> now
>   
>> ESB doesn't block :-)
>>     
>
> That sounds great! This is what bothered me most.
>   
I will test the ESB for some more scenarios and let you know tomorrow, 
after making a build available to you.

Thanks,
Ruwan
> Regards,
>    Eric
>
>
>   


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