OPENJPA-2922 disable JNDI lookup of EMF by default

To use this feature please set the following
system.property to true: emf_via_jndi_enabled

openjpa-kernel/src/main/resources/org/apache/openjpa/kernel/localizer.properties

@@ -137,6 +137,9 @@ end-trans-error: An exception occurred while ending the transaction.  This \
 not-bound: The file named "{0}" could not be found.
 naming-exception: A NamingException was thrown while obtaining the \
 	factory at "{0}" from JNDI.
+jndi-disabled-exception: Accessing the EntityManagerFactory via JNDI has been \
+    disabled. Set the system property {0} to 'true' if you want to use this \
+    feature.
 attach-deleted: The object "{0}" with id "{1}" has been deleted and \
 	cannot be attached.
 not-detachable: The class "{0}" does not declare the "detachable" metadata \

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

@@ -34,6 +34,7 @@
 import org.apache.openjpa.lib.conf.ConfigurationProvider;
 import org.apache.openjpa.lib.util.Localizer;
 import org.apache.openjpa.util.ImplHelper;
+import org.apache.openjpa.util.UserException;
 
 /**
  * Static helper methods for JPA users.
@@ -44,6 +45,11 @@
  */
 public class OpenJPAPersistence {
 
+    /**
+     * Set this System property to 'true' if you want to enable the EntityManager via JNDI
+     */
+    private static final String EMF_VIA_JNDI_ENABLED = "emf_via_jndi_enabled";
+
     private static final Localizer _loc =
         Localizer.forPackage(OpenJPAPersistence.class);
 
@@ -137,6 +143,10 @@ public static OpenJPAEntityManagerFactory getEntityManagerFactory(Map map) {
      */
     public static OpenJPAEntityManagerFactory createEntityManagerFactory
         (String jndiLocation, Context context) {
+        if (!"true".equalsIgnoreCase(System.getProperty(EMF_VIA_JNDI_ENABLED))) {
+            throw new UserException(_loc.get("jndi-disabled-exception", EMF_VIA_JNDI_ENABLED));
+        }
+
         if (jndiLocation == null)
             throw new NullPointerException("jndiLocation == null");