You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@shindig.apache.org by Ryan Baxter <rb...@gmail.com> on 2014/02/02 18:22:00 UTC
Re: Review Request 17228: Null pointer exception in gadget template processing

-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/17228/#review33399
-----------------------------------------------------------



/trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/DefaultTemplateProcessor.java
<https://reviews.apache.org/r/17228/#comment62854>

    If I remember correctly I believe that the result has all the templates replaced.  The first call to this method is the cached template, so yes it is shared between other threads.



/trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/XmlTemplateLibrary.java
<https://reviews.apache.org/r/17228/#comment62855>

    yeah I agree.  Chun Yan is on vacation for the next few weeks so i will change this before I deliver it.


- Ryan Baxter


On Jan. 28, 2014, 2:10 a.m., ChunYan Zhang wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/17228/
> -----------------------------------------------------------
> 
> (Updated Jan. 28, 2014, 2:10 a.m.)
> 
> 
> Review request for shindig, Dan Dumont, Ryan Baxter, Rich Thompson, Stanton Sievers, and Zhi Hong Yang.
> 
> 
> Bugs: SHINDIG-1893
>     https://issues.apache.org/jira/browse/SHINDIG-1893
> 
> 
> Repository: shindig
> 
> 
> Description
> -------
> 
> During our gadget development, several gadgets are referring to the same gadget template. The rendering of those gadgets is problematic sometimes.
> 
> When the problem occur, the Java stack trace look like this:
> 
> Stack Dump = java.lang.NullPointerException
>        at org.apache.xerces.dom.ParentNode.nodeListItem(Unknown Source)
>        at org.apache.xerces.dom.ParentNode.item(Unknown Source)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processChildNodes(DefaultTemplateProcessor.java:134)
>        at org.apache.shindig.gadgets.templates.tags.TemplateBasedTagHandler.processTemplate(TemplateBasedTagHandler.java:68)
>        at org.apache.shindig.gadgets.templates.tags.TemplateBasedTagHandler.process(TemplateBasedTagHandler.java:58)
>        at org.apache.shindig.gadgets.templates.XmlTemplateLibrary$LibraryTagHandler.process(XmlTemplateLibrary.java:305)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processElementInner(DefaultTemplateProcessor.java:341)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processElement(DefaultTemplateProcessor.java:246)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processNode(DefaultTemplateProcessor.java:154)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processChildNodes(DefaultTemplateProcessor.java:134)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processTemplate(DefaultTemplateProcessor.java:126)
>        at org.apache.shindig.gadgets.rewrite.TemplateRewriter.executeTemplates(TemplateRewriter.java:357)
>        at org.apache.shindig.gadgets.rewrite.TemplateRewriter.rewriteImpl(TemplateRewriter.java:177)
>        at org.apache.shindig.gadgets.rewrite.TemplateRewriter.rewrite(TemplateRewriter.java:129)
>        at org.apache.shindig.gadgets.render.HtmlRenderer.render(HtmlRenderer.java:88)
>        at org.apache.shindig.gadgets.render.Renderer.render(Renderer.java:101)
>        at org.apache.shindig.gadgets.servlet.GadgetRenderingServlet.render(GadgetRenderingServlet.java:112)
>        at org.apache.shindig.gadgets.servlet.GadgetRenderingServlet.doGet(GadgetRenderingServlet.java:90)
>        at javax.servlet.http.HttpServlet.service(HttpServlet.java:575)
> 
> Stack Dump2 =  java.lang.NullPointerException
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processText(DefaultTemplateProcessor.java:174)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processNode(DefaultTemplateProcessor.java:151)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processChildNodes(DefaultTemplateProcessor.java:134)
>        at org.apache.shindig.gadgets.templates.tags.TemplateBasedTagHandler.processTemplate(TemplateBasedTagHandler.java:68)
>        at org.apache.shindig.gadgets.templates.tags.TemplateBasedTagHandler.process(TemplateBasedTagHandler.java:58)
>        at org.apache.shindig.gadgets.templates.XmlTemplateLibrary$LibraryTagHandler.process(XmlTemplateLibrary.java:305)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processElementInner(DefaultTemplateProcess" severity="50" version="1.0.1">
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processElement(DefaultTemplateProcessor.java:247)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processNode(DefaultTemplateProcessor.java:154)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processChildNodes(DefaultTemplateProcessor.java:134)
>        at org.apache.shindig.gadgets.templates.DefaultTemplateProcessor.processTemplate(DefaultTemplateProcessor.java:126)
>        at org.apache.shindig.gadgets.rewrite.TemplateRewriter.executeTemplates(TemplateRewriter.java:358)
>        at org.apache.shindig.gadgets.rewrite.TemplateRewriter.rewriteImpl(TemplateRewriter.java:178)
>        at org.apache.shindig.gadgets.rewrite.TemplateRewriter.rewrite(TemplateRewriter.java:130)
>        at org.apache.shindig.gadgets.render.HtmlRenderer.render(HtmlRenderer.java:88)
>        at org.apache.shindig.gadgets.render.Renderer.render(Renderer.java:101)
>        at org.apache.shindig.gadgets.servlet.GadgetRenderingServlet.render(GadgetRenderingServlet.java:107)
>        at org.apache.shindig.gadgets.servlet.GadgetRenderingServlet.doGet(GadgetRenderingServlet.java:85)
>        at javax.servlet.http.HttpServlet.service(HttpServlet.java:693)
>        at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
> 
> The Xerces implementation is not thread safe and when we are caching the template we can potentially have multiple threads manipulating the same Element object.  This results in random null pointer exceptions as well as other odd exceptions in the code. The solution is to add synchronized to the key XML element.
> 
> 
> Diffs
> -----
> 
>   /trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/DefaultTemplateProcessor.java 1560262 
>   /trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/TemplateLibraryFactory.java 1560262 
>   /trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/XmlTemplateLibrary.java 1560262 
>   /trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/tags/FlashTagHandler.java 1560262 
>   /trunk/java/gadgets/src/main/java/org/apache/shindig/gadgets/templates/tags/TemplateBasedTagHandler.java 1560262 
> 
> Diff: https://reviews.apache.org/r/17228/diff/
> 
> 
> Testing
> -------
> 
> 
> Thanks,
> 
> ChunYan Zhang
> 
>