Autodetect classes in Hibernate from jar

问题

I have a JavaEE project with several entities with the following persistence.xml file:

...
<properties>
    <!-- Scan for annotated classes -->
    <property name="hibernate.archive.autodetection" value="class"/>
...

And it seems to work. The project is then deployed as a JAR to two different projects. In one them, the persistence.xml file is basically the same as the one above, i.e. uses the autodetection feature of Hibernate. However, it does not seem to work (because I think it needs to load search for the entities in a jar). When I tried manually listing all the entities in both xml files, everything works correctly.

Edit: It works with jar-file but only with the absolute path to the jar. Pretty useless for a team project.

回答1:

If I read you correctly, in the case where it does not work, the entities are in a different JAR than the persistence.xml that's used, right?

I think you're correct that's the problem. You need to tell Hibernate which JAR(s) to scan using the jar-file element. See the explanation and examples in the Hibernate docs here

回答2:

I think Hibernate only scans for JPA Entities inside jar files, and not in classes/ folders for example, or it only scans in the jar with the persistence.xml, or something like that. Instead of trying to bend the Hibernate scanner, I felt it would be easier to scan for entities myself. It is a lot easier than I anticipated.

 val entities = mutableListOf<Class<*>>()
AnnotationDetector(object : AnnotationDetector.TypeReporter {
    override fun reportTypeAnnotation(annotation: Class<out Annotation>?, className: String?) {
        entities.add(Class.forName(className))
    }

    override fun annotations(): Array<out Class<out Annotation>> = arrayOf(Entity::class.java)
}).detect("com.github")

VaadinOnKotlin.entityManagerFactory = Persistence.createEntityManagerFactory("sample", mapOf(AvailableSettings.LOADED_CLASSES to entities))

I have used the detector which is built-in in the atmosphere jar file; but you can use perhaps https://github.com/rmuller/infomas-asl or others as stated here: Scanning Java annotations at runtime The full code example is located here: https://github.com/mvysny/vaadin-on-kotlin/blob/master/vok-example-crud/src/test/java/com/github/vok/example/crud/Server.kt

None of the following helped: adding

<exclude-unlisted-classes>false</exclude-unlisted-classes>

to the persistence.xml file did nothing (according to doc it is ignored in JavaSE anyway); adding

<property name="hibernate.archive.autodetection" value="class, hbm" />

to the persistence.xml file did nothing (I'm not using hbm anyways). Don't waste your time trying to add those, they won't enable proper auto-scan.

回答3:

Using the empty element <jar-file></jar-file> works e.g. with WildFly 8.2.1.Final (Hibernate 4.3.7.Final) :) as mentioned here. (<property name="hibernate.archive.autodetection" value="class, hbm" /> did not work)

(but it did not work outside of WildFly for Eclipse-run JUnit tests where we had to remove it. Which is not a problem since the libraries are already in the classpath. The error was something like: java.net.URISyntaxException: Expected scheme-specific part at index 5: file:> => <java.lang.IllegalArgumentException: Unable to visit JAR file:. Cause: Expected scheme-specific part at index 5: file:> => <javax.persistence.PersistenceException: Unable to build entity manager factory)

来源：https://stackoverflow.com/questions/18012532/autodetect-classes-in-hibernate-from-jar