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POGroovy HTTP Builder: Empty POST response causes SAXParseException
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  1. POGroovy HTTP Builder: Empty POST response causes SAXParseException
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    copied!<p>I am implementing REST client for YouTrack API. I am getting an exception whenever my POST requests return empty response (there's just a valid header). The HTTP status code is 200. That's the stacktrace:</p> <pre><code>[Fatal Error] :-1:-1: Premature end of file. gru 03, 2013 10:34:49 AM groovyx.net.http.HTTPBuilder doRequest WARNING: Error parsing 'application/xml; charset=UTF-8' response org.xml.sax.SAXParseException; Premature end of file. at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source) at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source) at groovy.util.XmlSlurper.parse(XmlSlurper.java:181) at groovy.util.XmlSlurper.parse(XmlSlurper.java:234) at groovyx.net.http.ParserRegistry.parseXML(ParserRegistry.java:267) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90) at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1085) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:952) at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:909) at groovy.lang.Closure.call(Closure.java:423) at groovy.lang.Closure.call(Closure.java:439) at groovyx.net.http.HTTPBuilder.parseResponse(HTTPBuilder.java:561) at groovyx.net.http.HTTPBuilder.doRequest(HTTPBuilder.java:494) at groovyx.net.http.RESTClient.post(RESTClient.java:140) at groovyx.net.http.RESTClient$post.callCurrent(Unknown Source) at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141) at groovy.YouTrackRest.releaseVersion(YouTrackRest.groovy:66) at groovy.YouTrackRest$releaseVersion$0.call(Unknown Source) at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:45) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108) at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116) at YouTrack.run(YouTrack.groovy:13) [...] </code></pre> <p>I have debugged and found out what's the direct cause for that. I noticed that in groovyx.net.http.HTTPBuilder:492 before parsing it is checked whether response is empty but in my case the call entity.getContentLength() returns -1. After <a href="http://hc.apache.org/httpcomponents-core-ga/httpcore/apidocs/org/apache/http/entity/BasicHttpEntity.html#getContentLength%28%29" rel="nofollow">Apache documentation for HttpEntity</a> the number of bytes of the content, or a negative number if unknown</p> <p>My client implementation is very plain. I have worked the problem around by catching the HttpResponseException and asserting statusCode 200. I am still getting the stacktrace in my console, but that's probably just the logger setting. </p> <p>My implementation:</p> <pre><code>import groovyx.net.http.RESTClient class YouTrackRest extends RESTClient { [...] def activateVersion(versionNumber) { try { post( path: getVersionPath(versionNumber), body: [ colorIndex: ACTIVE_COLOR_INDEX, released: false, releaseDate: null, archived: false, newName: versionNumber ] ) } catch (HttpResponseException ex) { assert ex.response.status == 200 } } </code></pre> <hr> <p><strong>EDIT:</strong> These are the response headers</p> <pre><code>Server: nginx Date: Fri, 06 Dec 2013 10:36:10 GMT Content-Type: application/xml; charset=UTF-8 Transfer-Encoding: chunked Connection: keep-alive Vary: Accept-Encoding Set-Cookie: JSESSIONID=ny2s3cxwsvveya6vgwj2fmig;Path=/youtrack Expires: Thu, 01 Jan 1970 00:00:00 GMT Cache-Control: no-cache, no-store, no-transform, must-revalidate </code></pre> <p>Present <code>Transfer-Encoding: chunked</code> header explains missing 'Content-Length' header. That has to be the reason for unknown Content Length. Now, according to <a href="http://en.wikipedia.org/wiki/Chunked_transfer_encoding" rel="nofollow">Wikipedia</a> <em>The data transfer is terminated by a final chunk of length zero</em>. So maybe is this case the first chunk is also the last one? </p> <p>Both, the Web Server and the Http client library are third party for me. I would like to raise an issue by whoever misbehaves: </p> <ul> <li>either YouTrack REST WS <em>promisses</em> XML and returns nothing</li> <li>or <code>groovyx.net.http.HTTPBuilder</code> fails to process chunked encoded responses.</li> </ul> <p>I will be very helpful for some expertise to help me understand the problem. </p>
 

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