OPENJPA-1993: Deadlock Potential with XML ORM Processing

git-svn-id: https://svn.apache.org/repos/asf/openjpa/branches/1.0.x@1099630 13f79535-47bb-0310-9956-ffa450edef68

openjpa-kernel/src/main/java/org/apache/openjpa/conf/Compatibility.java

@@ -31,6 +31,7 @@ public class Compatibility {
     private boolean _quotedNumbers = false;
     private boolean _nonOptimisticVersionCheck = false;
     private boolean _flushBeforeDetach = true; 
+    private boolean _overrideContextClassloader = false;
 
     /**
      * Whether to require exact identity value types when creating object
@@ -192,4 +193,22 @@ public class Compatibility {
         _flushBeforeDetach = beforeDetach;
     }
 
+    /**
+     * Whether to temporally override the thread's Context Classloader when processing
+     * ORM XML documents to avoid deadlock potential with certain Classloader hierarchy
+     * configurations.  Defaults to false.
+     */
+    public boolean getOverrideContextClassloader() {
+        return _overrideContextClassloader;
+    }
+
+    /**
+     * Whether to temporally override the thread's Context Classloader when processing
+     * ORM XML documents to avoid deadlock potential with certain Classloader hierarchy
+     * configurations.  Defaults to false.
+     */
+    public void setOverrideContextClassloader(boolean overrideContextClassloader) {
+        _overrideContextClassloader = overrideContextClassloader;
+    }
+
 }

openjpa-lib/src/main/java/org/apache/openjpa/lib/meta/XMLMetaDataParser.java

@@ -106,6 +106,16 @@ public abstract class XMLMetaDataParser extends DefaultHandler
     private int _depth = -1;
     private int _ignore = Integer.MAX_VALUE;
     
+    private boolean _overrideContextClassloader = false;
+    
+    public boolean getOverrideContextClassloader() {
+    	return _overrideContextClassloader;
+    }
+    
+    public void setOverrideContextClassloader(boolean overrideCCL) {
+    	_overrideContextClassloader = overrideCCL;
+    }
+
     /**
      * Whether to parse element text.
      */
@@ -349,7 +359,19 @@ public abstract class XMLMetaDataParser extends DefaultHandler
         // parse the metadata with a SAX parser
         try {
             _sourceName = sourceName;
-            SAXParser parser = XMLFactory.getSAXParser(validating, true);
+            SAXParser parser = null;
+            ClassLoader oldLoader = null;
+
+            try {
+                if (_overrideContextClassloader == true) {
+
+                    oldLoader = (ClassLoader) AccessController.doPrivileged(
+                        J2DoPrivHelper.getContextClassLoaderAction());
+                    AccessController.doPrivileged(J2DoPrivHelper.setContextClassLoaderAction(
+                        XMLMetaDataParser.class.getClassLoader()));
+                }
+
+                parser = XMLFactory.getSAXParser(validating, true);
                 Object schema = null;
                 if (validating) {
                     schema = schemaSource;
@@ -379,6 +401,19 @@ public abstract class XMLMetaDataParser extends DefaultHandler
                 IOException ioe = new IOException(se.toString());
                 JavaVersions.initCause(ioe, se);
                 throw ioe;
+            } finally {
+                if (_overrideContextClassloader == true && oldLoader != null) {
+                    // Restore the old ContextClassloader
+                    try {
+                        AccessController.doPrivileged(J2DoPrivHelper.setContextClassLoaderAction(oldLoader));
+                    } catch (Throwable t) {
+                        if (_log != null && _log.isTraceEnabled()) {
+                            _log.trace(_loc.get("restore-contextclassloader-failed"));
+                        }
+                    }
+                    
+                }
+            }
         } finally {
             reset();
         }

openjpa-lib/src/main/java/org/apache/openjpa/lib/util/J2DoPrivHelper.java

@@ -789,6 +789,24 @@ public abstract class J2DoPrivHelper {
         };
     }
    
+    /**
+     * Return a PrivilegeAction object for Thread.currentThread
+     *   .setContextClassLoader().
+     * 
+     * Requires security policy:
+     *   'permission java.lang.RuntimePermission "setContextClassLoader";'
+     *   
+     * @return ClassLoader
+     */
+    public static final PrivilegedAction setContextClassLoaderAction(final ClassLoader loader) {
+        return new PrivilegedAction() {
+            public Object run() {
+                Thread.currentThread().setContextClassLoader(loader);
+                return Boolean.TRUE;
+            }
+        };
+    } 
+
     /**
      * Return a PrivilegedAction object for new Thread().
      * 

openjpa-lib/src/main/resources/org/apache/openjpa/lib/meta/localizer.properties

@@ -25,6 +25,8 @@ cant-diff-elems: Unable to differentiate between given package and class \
 	elements for class arg parsing.  No element can be a complete prefix of \
 	another.
 class-arg: Error extracting class information from "{0}".
+restore-contextclassloader-failed: An error occurred restoring the Thread's \
+    context classloader.
 parse-error: An error was encountered while parsing element "{0}".  Make sure \
 	the metadata file is correctly formatted.
 no-file: No source file found for "{0}".

openjpa-persistence/src/main/java/org/apache/openjpa/persistence/XMLPersistenceMetaDataParser.java

@@ -235,6 +235,14 @@ public class XMLPersistenceMetaDataParser
         if (repos != null
             && (repos.getValidate() & repos.VALIDATE_RUNTIME) != 0)
             setParseComments(false);
+        
+        if (repos != null) {
+            // Determine if the Thread Context Classloader needs to be temporally overridden to the Classloader
+            // that loaded the OpenJPA classes, to avoid a potential deadlock issue with the way Xerces
+            // handles parsers and classloaders.
+            this.setOverrideContextClassloader(repos.getConfiguration().getCompatibilityInstance().
+                getOverrideContextClassloader());
+        }
     }
 
     /**