Java threads backed up in XPathContext initialization and DTMManager.newInstance

Environment

• JBoss Enterprise Application Platform (EAP)
  • 6
  • 7

Issue

• Many java threads backed up in XPathContext initialization and resulting DTMManager.newInstance calls, for example:

   java.lang.Thread.State: BLOCKED (on object monitor)
	at java.util.zip.ZipFile$ZipFileInputStream.read(ZipFile.java:676)
	- waiting to lock <0x00000000a1931868> (a java.util.jar.JarFile)
	at java.util.zip.ZipFile$ZipFileInflaterInputStream.fill(ZipFile.java:415)
	at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:158)
	at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:283)
	at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:325)
	at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:177)
	- locked <0x00000000ec1c7a88> (a java.io.InputStreamReader)
	at java.io.InputStreamReader.read(InputStreamReader.java:184)
	at java.io.BufferedReader.fill(BufferedReader.java:154)
	at java.io.BufferedReader.readLine(BufferedReader.java:317)
	- locked <0x00000000ec1c7a88> (a java.io.InputStreamReader)
	at java.io.BufferedReader.readLine(BufferedReader.java:382)
	at org.apache.xml.dtm.ObjectFactory.findJarServiceProviderName(ObjectFactory.java:588)
	at org.apache.xml.dtm.ObjectFactory.lookUpFactoryClassName(ObjectFactory.java:373)
	at org.apache.xml.dtm.ObjectFactory.lookUpFactoryClass(ObjectFactory.java:206)
	at org.apache.xml.dtm.ObjectFactory.createObject(ObjectFactory.java:131)
	at org.apache.xml.dtm.ObjectFactory.createObject(ObjectFactory.java:101)
	at org.apache.xml.dtm.DTMManager.newInstance(DTMManager.java:142)
	at org.apache.xpath.XPathContext.<init>(XPathContext.java:114)
	at org.apache.xpath.XPathContext.<init>(XPathContext.java:321)

or

 java.lang.Thread.State: BLOCKED (on object monitor)
	at java.util.zip.ZipFile.getEntry(ZipFile.java:314)
	- waiting to lock <0x000000041ca4a870> (a java.util.jar.JarFile)
	at java.util.jar.JarFile.getEntry(JarFile.java:240)
	at java.util.jar.JarFile.getJarEntry(JarFile.java:223)
	at org.jboss.modules.JarFileResourceLoader.getJarEntry(JarFileResourceLoader.java:185)
	at org.jboss.modules.JarFileResourceLoader.getResource(JarFileResourceLoader.java:217)
	at org.jboss.modules.ModuleClassLoader.loadResourceLocal(ModuleClassLoader.java:351)
	at org.jboss.modules.ModuleClassLoader$1.loadResourceLocal(ModuleClassLoader.java:103)
	at org.jboss.modules.Module.getResourceAsStream(Module.java:635)
	at org.jboss.modules.ModuleClassLoader.findResourceAsStream(ModuleClassLoader.java:587)
	at org.jboss.modules.ConcurrentClassLoader.getResourceAsStream(ConcurrentClassLoader.java:362)
	at org.apache.xml.dtm.SecuritySupport12$6.run(SecuritySupport12.java:121)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.xml.dtm.SecuritySupport12.getResourceAsStream(SecuritySupport12.java:114)
	at org.apache.xml.dtm.ObjectFactory.findJarServiceProviderName(ObjectFactory.java:551)
	at org.apache.xml.dtm.ObjectFactory.lookUpFactoryClassName(ObjectFactory.java:375)
	at org.apache.xml.dtm.ObjectFactory.lookUpFactoryClass(ObjectFactory.java:208)
	at org.apache.xml.dtm.ObjectFactory.createObject(ObjectFactory.java:133)
	at org.apache.xml.dtm.ObjectFactory.createObject(ObjectFactory.java:103)
	at org.apache.xml.dtm.DTMManager.newInstance(DTMManager.java:137)
	at org.apache.xpath.XPathContext. (XPathContext.java:102)
	at org.apache.xpath.XPathAPI.eval(XPathAPI.java:225)
	at org.apache.xpath.XPathAPI.selectNodeList(XPathAPI.java:167)
	at org.apache.xpath.XPathAPI.selectNodeList(XPathAPI.java:147)
...

Resolution

• If possible, change application code to cache and reuse the XPathContext instance, which is thread-safe, instead of constantly recreating it.
• A more immediate fix would be to add -Dorg.apache.xml.dtm.DTMManager=org.apache.xml.dtm.ref.DTMManagerDefault or -Dcom.sun.org.apache.xml.internal.dtm.DTMManager= com.sun.org.apache.xml.internal.dtm.ref.DTMManagerDefault to the java options, so it does not need to read the jar file contents on every call.

Root Cause

• Content from issues.apache.org is not included.XALANJ-2540
• If the DTMManager class name is not found from the system property set in JVM options or a $JAVA_HOME/jre/lib/xalan.propreties file, then a more expensive jar look up is performed to find the value each time DTMManager.newInstance is called

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