Export utility throw an exception when exporting documents

I use xwiki-enterprise-jetty-hsqldb-2.2-milestone-2.zip, and imported my old pages selectively.

But now, the export utility failed to output an valid zip file. It should be around 20Mbytes, but now it returns a file of 11Mbytes. And there is an error in the log.

In 2.1.1, I have the same problem if I select "backup pack(preserve author)".

simba@wireless:~/XWiki Enterprise/webapps/xwiki$ 2010-01-29 21:46:17,158 http://192.168.1.213:8080/xwiki/bin/export/XWiki/Export?editor=globaladmin&section=Export WARN web.XWikiAction - Uncaught exception: Error number 0 in 11: Uncaught exception
Wrapped Exception: Java heap space
com.xpn.xwiki.XWikiException: Error number 0 in 11: Uncaught exception
Wrapped Exception: Java heap space
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:238)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:115)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.xpn.xwiki.wysiwyg.server.filter.ConversionFilter.doFilter(ConversionFilter.java:152)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:118)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.xpn.xwiki.plugin.webdav.XWikiDavFilter.doFilter(XWikiDavFilter.java:68)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.xpn.xwiki.web.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:295)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:112)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:536)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:930)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:747)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:405)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

Wrapped Exception:

java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:2882)
at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:100)
at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:390)
at java.lang.StringBuffer.append(StringBuffer.java:224)
at java.io.StringWriter.write(StringWriter.java:84)
at org.dom4j.io.XMLWriter.writeElement(XMLWriter.java:962)
at org.dom4j.io.XMLWriter.writeNode(XMLWriter.java:1301)
at org.dom4j.io.XMLWriter.writeElementContent(XMLWriter.java:1136)
at org.dom4j.io.XMLWriter.writeElement(XMLWriter.java:954)
at org.dom4j.io.XMLWriter.writeNode(XMLWriter.java:1301)
at org.dom4j.io.XMLWriter.writeElementContent(XMLWriter.java:1136)
at org.dom4j.io.XMLWriter.writeElement(XMLWriter.java:954)
at org.dom4j.io.XMLWriter.writeNode(XMLWriter.java:1301)
at org.dom4j.io.XMLWriter.write(XMLWriter.java:344)
at com.xpn.xwiki.doc.XWikiDocument.toXML(XWikiDocument.java:3172)
at com.xpn.xwiki.doc.XWikiDocument.toXML(XWikiDocument.java:3228)
at com.xpn.xwiki.plugin.packaging.Package.addToZip(Package.java:941)
at com.xpn.xwiki.plugin.packaging.Package.export(Package.java:332)
at com.xpn.xwiki.plugin.packaging.PackageAPI.export(PackageAPI.java:212)
at com.xpn.xwiki.plugin.packaging.PackageAPI.backupWiki(PackageAPI.java:261)
at com.xpn.xwiki.web.ExportAction.exportXAR(ExportAction.java:262)
at com.xpn.xwiki.web.ExportAction.render(ExportAction.java:60)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:214)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:115)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)