Is it possible to have persistence.xml in a location other than META-INF?

This solution worked for me

    Thread.currentThread().setContextClassLoader(new ClassLoader() {
        @Override
        public Enumeration<URL> getResources(String name) throws IOException {
            if (name.equals("META-INF/persistence.xml")) {
                return Collections.enumeration(Arrays.asList(new File("conf/persistence.xml")
                        .toURI().toURL()));
            }
            return super.getResources(name);
        }
    });
    Persistence.createEntityManagerFactory("test");

The createEntityManagerFactory methods search for persistence.xml files within the META-INF directory of any CLASSPATH element. if your CLASSPATH contains the conf directory, you could place an EntityManagerFactory definition in conf/META-INF/persistence.xml

The ClassLoader may be a URLClassLoader, so try it this way:

        final URL alternativePersistenceXmlUrl = new File("conf/persistence.xml").toURI().toURL();

    ClassLoader output;

    ClassLoader current = Thread.currentThread().getContextClassLoader();

    try{

        URLClassLoader parent = (URLClassLoader)current;

        output = new URLClassLoader(parent.getURLs(), parent){

            @Override
            public Enumeration<URL> getResources(String name) throws IOException {

                if (name.equals("META-INF/persistence.xml")) {

                    return Collections.enumeration(Arrays.asList(alternativePersistenceXmlUrl));
                }

                return super.getResources(name);
            }
        };
    }catch(ClassCastException ignored) {

        output = new ClassLoader() {

            @Override
            public Enumeration<URL> getResources(String name) throws IOException {

                if (name.equals("META-INF/persistence.xml")) {

                    return Collections.enumeration(Arrays.asList(alternativePersistenceXmlUrl));
                }

                return super.getResources(name);
            }
        };
    }

It should work. Works for me under certain test etc conditions. Please this is a hack and should not be used in production.

If you are using EclipseLink you can set the persistence.xml location with the persistence unit property, "eclipselink.persistencexml".

properties.put("eclipselink.persistencexml", "/org/acme/acme-persistence.xml");
EntityManagerFactory factory = Persistence.createEntityManagerFactory("acme", properties);