The repository home appears to be already locked by the current process.

Caused by: javax.jcr.RepositoryException: The repository home /home/data/jackrabbit/home appears to be already locked by the current process.
at org.apache.jackrabbit.core.util.RepositoryLock.tryLock(RepositoryLock.java:183)
at org.apache.jackrabbit.core.util.RepositoryLock.acquire(RepositoryLock.java:138)
at org.apache.jackrabbit.core.RepositoryImpl.<init>(RepositoryImpl.java:302)
at org.apache.jackrabbit.core.RepositoryImpl.create(RepositoryImpl.java:673)
at org.apache.jackrabbit.core.TransientRepository$2.getRepository(TransientRepository.java:231)
at org.apache.jackrabbit.core.TransientRepository.startRepository(TransientRepository.java:279)
at org.apache.jackrabbit.core.TransientRepository.login(TransientRepository.java:375)
at com.liferay.portal.jcr.jackrabbit.JCRFactoryImpl.createSession(JCRFactoryImpl.java:67)
at com.liferay.portal.jcr.JCRFactoryUtil.createSession(JCRFactoryUtil.java:43)
at com.liferay.portal.jcr.JCRFactoryUtil.createSession(JCRFactoryUtil.java:47)
at com.liferay.documentlibrary.util.JCRHook.getFileAsStream(JCRHook.java:457)

synchronized (identifier) {
if (null != System.getProperty(identifier))

{ // note that the newly acquired (redundant) file lock // is deliberately *not* released because this could // potentially cause, depending on the implementation, // the previously acquired lock(s) to be released // as well throw new RepositoryException( "The repository home " + directory + " appears to be" + " already locked by the current process."); }

else {
try

{ System.setProperty(identifier, identifier); }

catch (SecurityException e)

{ LOG.warn("Unable to set system property: " + identifier, e); }

}
}

but I already use jdk1.6, anyone can help me?