[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2990) Bad usage of ClassLoader.loadClass() for Java6 in SerializationHelper$CustomObjectInputStream - deserialization bottleneck for arrays
Gail Badner (JIRA)
noreply at atlassian.com
Tue Aug 25 20:04:15 EDT 2009
[ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33849#action_33849 ]
Gail Badner commented on HHH-2990:
----------------------------------
https://jira.jboss.org/jira/browse/JBPAPP-906
https://jira.jboss.org/jira/browse/JBPAPP-2277
> Bad usage of ClassLoader.loadClass() for Java6 in SerializationHelper$CustomObjectInputStream - deserialization bottleneck for arrays
> -------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HHH-2990
> URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2990
> Project: Hibernate Core
> Issue Type: Bug
> Affects Versions: 3.2.5
> Environment: Hibernate 3.2.5, Java 6 Sun (any), any platform (tested Linux x64, Mac x64 (J6dp1))
> Reporter: Tom Eicher
> Assignee: Gail Badner
> Fix For: 3.2.x, 3.3.x, 3.5
>
>
> Sun has "clarified" (others say modified) the API of "ClassLoader.loadClass()" and no longer allows this to be called for arrays, e.g. String[].
> ( see: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6500212 and duplicates )
> and states that this has always been very unstable to use/do in the first place.
> So trying to load an array of something using this method results in ClassNotFoundException.
> The correct thing to do is call Class.forName(className,false,myClassLoader); instead of myClassLoader.loadClass(className);
> In SerializationHelper$CustomObjectInputStream.resolveClass() we do
> ClassLoader loader = Thread.currentThread().getContextClassLoader();
> try {
> resolvedClass = loader.loadClass(className);
> log.trace("Class resolved through context class loader");
> }
> catch(ClassNotFoundException e) {
> log.trace("Asking super to resolve");
> resolvedClass = super.resolveClass(v);
> }
> which results in the deserialization process for a String[] always searching String[] in all the application's jars/wars/etc before really loading it.
> The bad thing is, loadClass() is synchronized.
> In our case, we have multiple threads loading database rows containing String[]s, which results in one Thread doing
> INFO | jvm 1 | 2007/11/30 16:56:44 | java.lang.Thread.State: RUNNABLE
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.util.zip.ZipFile.getEntry(Native Method)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.util.zip.ZipFile.getEntry(ZipFile.java:149)
> INFO | jvm 1 | 2007/11/30 16:56:44 | - locked <0x00002aaab4047c20> (a java.util.jar.JarFile)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.util.jar.JarFile.getEntry(JarFile.java:206)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.util.jar.JarFile.getJarEntry(JarFile.java:189)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at sun.misc.URLClassPath$JarLoader.getResource(URLClassPath.java:754)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at sun.misc.URLClassPath.getResource(URLClassPath.java:168)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.net.URLClassLoader$1.run(URLClassLoader.java:192)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.security.AccessController.doPrivileged(Native Method)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
> INFO | jvm 1 | 2007/11/30 16:56:44 | - locked <0x00002aaab4025998> (a org.apache.catalina.loader.StandardClassLoader)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
> INFO | jvm 1 | 2007/11/30 16:56:44 | - locked <0x00002aaab4095a68> (a org.apache.catalina.loader.StandardClassLoader)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1346)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.hibernate.util.SerializationHelper$CustomObjectInputStream.resolveClass(SerializationHelper.java:263)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1575)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.io.ObjectInputStream.readArray(ObjectInputStream.java:1624)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1323)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.hibernate.util.SerializationHelper.deserialize(SerializationHelper.java:210)
> and all other threads doing nothing
> INFO | jvm 1 | 2007/11/30 16:56:44 | java.lang.Thread.State: BLOCKED (on object monitor)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.lang.ClassLoader.loadClass(ClassLoader.java:295)
> INFO | jvm 1 | 2007/11/30 16:56:44 | - waiting to lock <0x00002aaab4095a68> (a org.apache.catalina.loader.StandardClassLoader)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1346)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at org.hibernate.util.SerializationHelper$CustomObjectInputStream.resolveClass(SerializationHelper.java:263)
> INFO | jvm 1 | 2007/11/30 16:56:44 | at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1575)
> (rest of stack trace identical to above)
> This can easily be worked around by setting the compatibility property
> -Dsun.lang.ClassLoader.allowArraySyntax=true
> however a) this workaround might not be around for long and b) most people will never find this bottleneck, therefore will not apply the workaround.
> For our case, we got a 35% performance increase just be setting this property (and not a single loadClass() or ZipFile.getEntry() in any thread dump any more).
> Cheers, Tom.
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