OSGi + JPA（postgresql）

Question

我尝试在 OSGi 中使用 JPA 并遇到此异常：

 javax.persistence.PersistenceException: No Persistence provider for EntityManager named test 

META-INF 中有简单的实体类，文件“persistence.xml”：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="test" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>org.test.Room</class>
    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:postgresql://localhost:5432/test"/>
      <property name="javax.persistence.jdbc.password" value="12345"/>
      <property name="javax.persistence.jdbc.driver" value="org.postgresql.Driver"/>
      <property name="javax.persistence.jdbc.user" value="postgres"/>

    </properties>
  </persistence-unit>
</persistence>

Activator：

package org.test;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

public class Activator implements BundleActivator {

    private static BundleContext context;
    static BundleContext getContext() {
        return context;
    }

    public void start(BundleContext bundleContext) throws Exception {
        Activator.context = bundleContext;
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("test");
    }

    public void stop(BundleContext bundleContext) throws Exception {
        Activator.context = null;
    }
}

Manifest.mf：

Manifest-Version: 1.0
Bundle-ManifestVersion: 2
Bundle-Name: Test
Bundle-SymbolicName: org.test
Bundle-Version: 1.0.0.qualifier
Bundle-Activator: org.test.Activator
Import-Package: javax.persistence;version="2.0.3", 
 org.osgi.framework;version="1.3.0",
 org.postgresql;version="8.3.604"
Bundle-RequiredExecutionEnvironment: JavaSE-1.7

和错误：

org.osgi.framework.BundleException：异常 包 org.test 的 org.test.Activator.start()。在

org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:734)

<块引用>

在 org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:683) 在 org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:381) 在 org.eclipse.osgi.framework.internal.core.AbstractBundle.resume(AbstractBundle.java:389) 在 org.eclipse.osgi.framework.internal.core.Framework.resumeBundle(Framework.java:1131) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:559) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:544) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.incFWSL(StartLevelManager.java:457) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:243) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:438) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:1) 在 org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230) 在 org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:340) 引起原因：javax.persistence.PersistenceException：无持久性 EntityManager 的提供者名为 test at javax.persistence.Persistence.createEntityManagerFactory（未知 来源）位于 javax.persistence.Persistence.createEntityManagerFactory（未知 来源）位于 org.test.Activator.start(Activator.java:23) 处 org.eclipse.osgi.framework.internal.core.BundleContextImpl$1.run(BundleContextImpl.java:711) 在 java.security.AccessController.doPrivileged（本机方法）处 org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:702) ... 12个更多根异常： javax.persistence.PersistenceException：没有名为 test 的 EntityManager 的持久性提供程序 javax.persistence.Persistence.createEntityManagerFactory（未知 来源）位于 javax.persistence.Persistence.createEntityManagerFactory（未知 来源）位于 org.test.Activator.start(Activator.java:23) 处 org.eclipse.osgi.framework.internal.core.BundleContextImpl$1.run(BundleContextImpl.java:711) 在 java.security.AccessController.doPrivileged（本机方法）处 org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:702) 在 org.eclipse.osgi.framework.internal.core.BundleContextImpl.start(BundleContextImpl.java:683) 在 org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:381) 在 org.eclipse.osgi.framework.internal.core.AbstractBundle.resume(AbstractBundle.java:389) 在 org.eclipse.osgi.framework.internal.core.Framework.resumeBundle(Framework.java:1131) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:559) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:544) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.incFWSL(StartLevelManager.java:457) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:243) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:438) 在 org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:1) 在 org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230) 在 org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:340)

persistence.xml 在一个简单的 java 项目中可以正常工作，但是在 OSGi 插件中我遇到了这个问题。怎么了？

Answer 1

您需要将 persistence.xml 路径添加为 MANIFEST.MF 标头，如下所示：

Meta-Persistence: META-INF/persistence.xml

尽管对于 EclipseLink，可能需要以下标头（标头值是逗号分隔的 PU 名称列表）：

JPA-PersistenceUnits: test