Eclipse Warnings: class javax.persistence.* not found

问题

This is my first time really playing around with Java development using Eclipse. I am trying to use EclipseLink's implementation of the JPA. I moved all of my entities into a separate package "entities". I have the persistence.xml in a separate JPA project called "dataModeling".

Everything builds and runs fine.

Just about every project depends on my entities. However, I'm seeing a warning Class javax.persistence.Entity not found - continuing with a stub., etc. showing up because the dependent projects don't reference EclipseLink.

The solution is to go into each dependent project's properties and under Java Build Path > Libraries, click Add Library, then User Library and then select EclipseLink.

However, to me, it doesn't make sense to reference EclipseLink in every project! That's an implementation detail I don't want to burden other projects with. It looks like this is happening because the other projects see the annotations and don't recognize them.

So the real question is: how can I use JPA (via annotations) without every other project needing to reference my JPA implementation?

回答1:

Your pom.xml should contain:

<dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>eclipselink</artifactId>
    <version>2.5.1</version>
</dependency>
<dependency>
    <groupId>org.eclipse.persistence</groupId>
    <artifactId>javax.persistence</artifactId>
    <version>2.0.0</version>
    <scope>compile</scope>
</dependency>

the first one is Eclipse-Link (which you already have), the second one is Persistence API which is lacking.

If you are not using maven - make sure that javax.persistence-2.0.0.jar is on your classpath.

Note that this is version 2.0.0, the newest is 2.1.0

update The project which makes use of EntityManager should have these dependences. Putting entities and persistence.xml in separate jar file still requires the other project that uses it to fulfill above dependencies.

回答2:

Thanks to @neil-stockton and @chris, I was able to figure out what was going on. Most JPA implementations have a copy of the javax.persistence JAR floating around somewhere. Most of them are bundled with everything else, leading to my dependency nightmare. There doesn't appear to be a de facto implementation floating around.

In my case, I used the copy that showed up under my Eclipse plugins directory. These annotations were truly empty in that did not have any unwanted dependencies. The JAR file (javax.persistence._<version>.jar) only showed up after I added the Dali and EclipseLink plugins (one or the other).

来源：https://stackoverflow.com/questions/24812730/eclipse-warnings-class-javax-persistence-not-found