what is the right path to refer a jar file in jpa persistence.xml in a web app?

Solution 1:

Taking a look at jsr always works!

8.2.1.6.3 Jar Files

One or more JAR files may be specified using the jar-file elements instead of, or in addition to the mapping files specified in the mapping-file elements. If specified, these JAR files will >be searched for managed persistence classes, and any mapping metadata annotations found on them will be pro-cessed, or they will be mapped using the mapping annotation defaults defined by this specification. Such JAR files are specified relative to the directory or jar file that contains the root of the persis-tence unit.

The following examples illustrate the use of the jar-file element to reference additional persistence classes. These examples use the convention that a jar file with a name terminating in “PUnit” contains the persistence.xml file and that a jar file with a name terminating in “Entities” contains additional persistence classes.

Example 1:
app.ear  
   lib/earEntities.jar  
   earRootPUnit.jar (with META-INF/persistence.xml )  
persistence.xml contains:  
   <jar-file>lib/earEntities.jar</jar-file>  

Example 2:
app.ear
   lib/earEntities.jar
   lib/earLibPUnit.jar (with META-INF/persistence.xml )
persistence.xml contains:
   <jar-file>earEntities.jar</jar-file>

Example 3:
app.ear
   lib/earEntities.jar
   ejbjar.jar (with META-INF/persistence.xml )
persistence.xml contains:
   <jar-file>lib/earEntities.jar</jar-file>

Example 4:
app.ear
    war1.war
       WEB-INF/lib/warEntities.jar
       WEB-INF/lib/warPUnit.jar (with META-INF/persistence.xml )
persistence.xml contains:
    <jar-file>warEntities.jar</jar-file>

Example 5:
app.ear
   war2.war
      WEB-INF/lib/warEntities.jar
      WEB-INF/classes/META-INF/persistence.xml
persistence.xml contains:
   <jar-file>lib/warEntities.jar</jar-file>

Example 6:
app.ear
    lib/earEntities.jar
    war2.war
    WEB-INF/classes/META-INF/persistence.xml
 persistence.xml contains:
    <jar-file>../../lib/earEntities.jar</jar-file>

Example 7:
app.ear
   lib/earEntities.jar
   war1.war
   WEB-INF/lib/warPUnit.jar (with META-INF/persistence.xml )
persistence.xml contains:
   <jar-file>../../../lib/earEntities.jar</jar-file>

As you see there is no example for war files, all war files in the examples above are inside ear files!
But I tested in war files and it works just when I specify the absolute path of jar files and it is not a good approach for production environment!

Solution 2:

just in case someone else stumbles upon this: the jar-file-statement is only valid. when the persistence-unit is deployed as part of an Enterprise Archives (.ear) - in every other case (.war), the persistence.xml must reside in /META-INF/ and cannot refrence classes that live outside the persistence-unit (see: http://javahowto.blogspot.com/2007/06/where-to-put-persistencexml-in-web-app.html). So, as far as I know, there is no way to have a persistence.xml living in WEB-INF/classes/META-INF that references classes that do not live in WEB-INF/classes.

Solution 3:

war2.war
      WEB-INF/lib/warEntities.jar
      WEB-INF/classes/META-INF/persistence.xml
persistence.xml contains:
   <jar-file>lib/warEntities.jar</jar-file>

this format works for war file. Im using Wildlfy 8.2.0 and JPA 2.1