EBS R12 -- Problem in XML publisher report outputs (when charts are added)

This blog post will be a little thing for the newbies. I will try to give you the general concept and methods that we use in fixing EBS tech. errors.
Here is the famous 4 steps (Debug,analyze the related log ,search and apply the solution) which need to be taken for fixing a weird problem in EBS. (it may not be weird for anyone :))
This time , we are dealing with the XML BI Publisher, which comes built-in with EBS.
When we talk about XML/BI publisher, most of the time we are actually talking about java.
Also, when we start our analysis for diagnosing the XML/BI Publisher errors, we most of the time, find ourselves reviewing the OPP log.

Note that: For dealing with the XML publisher-related errors, we review the logs in the following sequence.

1)Conc request log 2) OPP(Output Post Processor) log 3)XDO log <after enabling xdo debug>

The problem that we are dealing in this example is an XML Publisher output problem. That is, in this example, we are dealing with a problematic situation where XML Publisher report output(PDF in this case) can not be created, when a chart(graph) is added to a specific report. (custom report)

Here is the usual way of solving these kinds of problems.. ( We find the cause by analyzing the log,  we search it if it is not something that we know, we apply the solution once it is find)

First, we analyze.. This time it is in the opp.log.

OPP LOG:

[12/2/16 3:53:03 PM] [UNEXPECTED] [601115:RT590163] java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
         ...
         ....
         ......   (output truncated)
at oracle.apps.xdo.oa.schema.server.TemplateHelper.runProcessTemplate(TemplateHelper.java:5936)
at oracle.apps.xdo.oa.schema.server.TemplateHelper.processTemplate(TemplateHelper.java:3459)
at oracle.apps.xdo.oa.schema.server.TemplateHelper.processTemplate(TemplateHelper.java:3548)
at oracle.apps.fnd.cp.opp.XMLPublisherProcessor.process(XMLPublisherProcessor.java:302)
at oracle.apps.fnd.cp.opp.OPPRequestThread.run(OPPRequestThread.java:176)
Caused by: oracle.xdo.parser.v2.XPathException: Extension function error: Error invoking 'chart_svg':'java.lang.NoClassDefFoundError: Could not initialize class sun.awt.X11GraphicsEnvironment'
at oracle.xdo.parser.v2.XSLStylesheet.flushErrors(XSLStylesheet.java:1534)
at oracle.xdo.parser.v2.XSLStylesheet.execute(XSLStylesheet.java:521)
at oracle.xdo.parser.v2.XSLStylesheet.execute(XSLStylesheet.java:489)
at oracle.xdo.parser.v2.XSLProcessor.processXSL(XSLProcessor.java:271)
at oracle.xdo.parser.v2.XSLProcessor.processXSL(XSLProcessor.java:155)
at oracle.xdo.parser.v2.XSLProcessor.processXSL(XSLProcessor.java:192)
... 18 more

We find (acutally sense) the root cause by looking at the log. "InvocationTargetException" is generic one, so we don't go with it. 

 On the other hand, we go with the Error invoking 'chart_svg', as it is written in the line starting with "Caused by" and it seems promising: ) 

After choosing our keyword, we go to Oracle Support and use our keyword to do our search.

ORACLE SUPPORT SEARCH KEYWORD: 

Error invoking 'chart_svg' 

A support search like this, I mean a search with correct keyword, brings us to the solution.

 

SOLUTION: 

XML Publisher Report With Pie Chart Error invoking 'chart_svg':'java.lang.NoClassDefFoundError (Doc ID 1992454.1) 

Well, in this case, XML/BI Publisher needs to have a correct DISPLAY set, as it was trying to using "X libraries" to draw the graph/chart that is supposed to be added to the output of the XML publisher report.

So, we stop the apps tier services, modify the context file (DISPLAY context variable), modify the start scripts in $ADMIN_SCRIPTS_HOME directory. (only the ones in which the DISPLAY env variable is set), run autoconfig on apps tier and start the apps tier services.