[FIXED] JPA/Hibernate finds no mapped classes after deployment

Issue

Short Version

I've got a Java-project which uses JPA 2.0 with Hibernate 4.3.4. All is fine when I run it inside Eclipse. But when I let Eclipse export a runnable JAR, the trouble begins and the program crashes due to a seemingly missing persistence unit...

javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyDBManager
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:61)

... or seemingly unmapped classes...

3024 Thread-4| FATAL DbManager : DBManager could not load countries from database.
java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: Country is not mapped [SELECT x FROM Country x]
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1750)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1677)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1683)
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:331)

Background

Depending on the kind of export (extracting vs. packaging vs. copying libraries), I run into different errors which resist solving. The furthest I get is with the last approach, which is also the one I have to choose for license reasons, so let's focus on that one.

In this case the exported JAR fails to look into its persistence.xml. I will specify that later but first some background information...

Folder Structure

• some_folder
  • myproject_lib
  • myproject.jar
    • root of my project's package structure
    • meta-inf
      • persistence.xml

File persistence.xml

<persistence xmlns="http://java.sun.com/xml/ns/persistence" version="2.0">
    <persistence-unit name="MyDBManager" transaction-type="RESOURCE_LOCAL">
        <!-- <exclude-unlisted-classes>false</exclude-unlisted-classes> -->
        <!-- <class>isi.eload.core.Country</class> -->
        <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
            <!-- Do not define a connection here - this is done by the DbManager according to the command line arguments -->
            <property name="hibernate.id.new_generator_mappings" value="true" />
            <!-- <property name="hibernate.archive.autodetection" value="class, hbm" /> -->
        </properties>
    </persistence-unit>
</persistence>

I played around with the commented lines, once I felt that the xml is actually processed (see below) but that didn't help.

JPA/Hibernate JARs

Essentially the ones from the 4.3.4 Final Release:

• antlr-2.7.7
• dom4j-1.6.1
• hibernate-commons-annotations-4.0.4.Final
• hibernate-core-4.3.4.Final
• hibernate-entitymanager-4.3.4.Final
• hibernate-jpa-2.1-api-1.0.0.Final
• jandex-1.1.0.Final
• javassist-3.18.1-GA
• jboss-logging-3.1.3.GA
• jboss-logging-annotations-1.2.0.Beta1
• jboss-transaction-api_1.2_spec-1.0.0.Final

.

Failing with persistence.xml

Packaged meta-inf

As I hinted at before, the exported JAR fails to properly process the persistence.xml. When I execute it in the above folder structure, the following exception is thrown:

javax.persistence.PersistenceException: No Persistence provider for EntityManager named MyDBManager
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:61)

This exception is usually thrown when the file was found but the persistence unit name given to Persistence.createEntityManagerFactory does not match any persistence unit declared in the files. But this is definitely not the case here! I have no good idea, why this exception is thrown.

When I edit the JAR file (though I'm not sure that such tampering is not causing problems on its own) and empty or remove the persistence.xml, the error stays the same.

Another meta-inf

My first response was to copy a meta-inf folder next to the JAR:

• myproject_lib
• myproject.jar
  • ... unchanged ...
• meta-inf
  • persistence.xml

This seems to work, as an entity manager factory can now be created. But then no Entities are found and I think this is related to the fact that the persistence.xml, which is actually used, is not "on the same class path" as the JAR file.

Is there a link or an idea for how I can fix this? Preferably by forcing the JAR file to use the meta-inf folder which it contains itself.

Solution

META-INF needs to be in upper case. If Java is attempting to access the filesystem on Windows (or OS X in that regard) META-INF/persistence.xml will be automatically translated to meta-inf/persistence.xml by the operating system. Once you package it up to a JAR it becomes case sensitive and stops working.

Answered By - anttix