ExtensionsFilter is not THREAD SAFE
-----------------------------------
Key: MYFACES-1137
URL: http://issues.apache.org/jira/browse/MYFACES-1137
Project: MyFaces
Type: Bug
Components: Tomahawk
Versions: Nightly
Environment: JDK 1.5, OC4J
Reporter: Claudio Tasso
Priority: Critical
Using Tomahawk I experimented some problems with the ExtensionFilter, in
particular some errors occur when the MyFaces javascript is written inside the
body of the response.
This is the typical error message:
java.lang.StringIndexOutOfBoundsException
at java.lang.StringBuffer.insert(StringBuffer.java:905)
at
org.apache.myfaces.renderkit.html.util.DefaultAddResource.writeMyFacesJavascriptBeforeBodyEnd(DefaultAddResource.java:658)
at
org.apache.myfaces.component.html.util.ExtensionsFilter.doFilter(ExtensionsFilter.java:138)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview
4].server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:699)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview
4].server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:397)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview
4].server.http.HttpRequestHandler.doProcessRequest(HttpRequestHandler.java:833)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview
4].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:430)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview
4].server.http.HttpRequestHandler.serveOneRequest(HttpRequestHandler.java:216)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview 4].server.http.HttpRequestHandler.run(HttpRequestHandler.java:119)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview 4].server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)
at
oracle.oc4j.network.ServerSocketReadHandler$SafeRunnable.run(ServerSocketReadHandler.java:215)
at com.evermind[Oracle Containers for J2EE 10g (10.1.3.0.0) - Developer
Preview
4].util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:303)
at java.lang.Thread.run(Thread.java:534)
This error occurs randomly. Looking at the AddResourceFactory code, I see that
only one AddResource instace exists and this instance is shared among the
servlet threads.
The ExtensionFilter calulates the beforeBodyEndPosition value (which is a
DefaultAddResource property) and then this value is used for writing inside a
StringBuffer which should contain the response body.
This is the code in ExtensionFilter the I'm talking about:
addResource.parseResponse(extendedRequest, extendedResponse.toString(),
servletResponse);
addResource.writeMyFacesJavascriptBeforeBodyEnd(extendedRequest,
servletResponse);
The problem is that a typical race condition seems to happen.
The beforeBodyEndPosition value is calulated for Thread1, which is suspended.
Then, Thread 2 starts and it modifies the beforeBodyEndPosition value. When
Thread2 terminates, Thread1 resumes and it tries to write inside its body
response at an index which is no more valid.
The reason of this behaviour is (according to me) the following: there is just
one instance of DefaultAddResource, so the execution of
AddResource.parseResponse and AddResource.writeMyFacesJavascriptBeforeBodyEnd
should be atomic.
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