[FOP-2762] Serialisation issues when accessibility enabled and conserve-memory enabled

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.1, 2.2
• Component/s: renderer/afp, renderer/pdf
• Flags: Important
• Assignee: Simon Steiner
• Reporter: Vincent Bonnefoy
• Created: 28/Nov/17 17:15
• Updated: 04/Jul/19 13:49
• Resolved: 04/Jul/19 13:49

Description

When rendering PDF or AFP using the conserve-memory and accessibility flag "on" a serialisation error is thrown.

I'm using the "representation of document in intermediate format XML" and get the following error when the CachedRenderPagesModel.java class is trying to save the page to disk.

SEVERE: Error while serializing page 1. Reason: java.io.NotSerializableException: org.apache.fop.render.intermediate.IFStructureTreeBuilder$IFStructureTreeElement
java.io.NotSerializableException: org.apache.fop.render.intermediate.IFStructureTreeBuilder$IFStructureTreeElement

It then leads to a NullPointerException when later the process tries to retrieve the page.

I saw the same behaviour when the output is set as "pdf" and uses the PDFStructElem.java object even though that's not the mode I'm using that also needs to be fixed.

SEVERE: Error while serializing page 1. Reason: java.io.NotSerializableException: org.apache.fop.pdf.PDFStructElem$Placeholder
java.io.NotSerializableException: org.apache.fop.pdf.PDFStructElem$Placeholder

I'm using fop within a java application but I reproduced using fop binaries:

• name.xml - comes from the fop website
• name2fo.xsl - comes from the fop website
  A page citation reference has been added to force the conserve-memory flag to serialise the page to disk for unresolved references.
• cfg-accessibility.xml - comes from the fop website
  2 renderer have been added, PDF and AFP, since that's the ones I'm using.
  The <accessibility>true</accessibility> flag has been turned on

fop -xml name.xml -xsl name2fo.xsl -c cfg-accessibility.xml out.pdf -conserve