Datanucleus RDBMS JPA jar依赖

Question

我配置并使用Datanucleus JPA连接到MySQL。我用datanucleus-enhancer-plugin编译了类和增强的实体。我可以使用mvn exec:java运行我的应用程序，也可以在使用lib (jar依赖项)创建存档之后运行它。

当我创建一个jar (带有依赖项的jar)时，问题出现了。我得到了这个错误：

javax.persistence.PersistenceException: Explicit persistence provider error(s) occurred for "mysql" after trying the following discovered implementations: org.datanucleus.api.jpa.PersistenceProviderImpl from provider: org.datanucleus.api.jpa.PersistenceProviderImpl
    at javax.persistence.Persistence.createPersistenceException(Persistence.java:244)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:186)
    at cantina.crawler.util.JpaUtil.getRdbmsEntityManager(JpaUtil.java:29)
    at cantina.crawler.bolt.SiteDetectorBolt.prepare(SiteDetectorBolt.java:32)
    at backtype.storm.daemon.executor$fn__4050$fn__4059.invoke(executor.clj:610)
    at backtype.storm.util$async_loop$fn__465.invoke(util.clj:375)
    at clojure.lang.AFn.run(AFn.java:24)
    at java.lang.Thread.run(Thread.java:722)
Caused by: org.datanucleus.exceptions.NucleusException: Error creating handler of type "persistence" for metadata parsing : MetaData handler plugin "persistence" was not found. Please check your CLASSPATH and plugin specification.
    at org.datanucleus.metadata.xml.MetaDataParser.parseMetaDataStream(MetaDataParser.java:269)
    at org.datanucleus.metadata.xml.MetaDataParser.parseMetaDataURL(MetaDataParser.java:137)
    at org.datanucleus.metadata.MetaDataUtils.parsePersistenceFiles(MetaDataUtils.java:956)
    at org.datanucleus.api.jpa.JPAEntityManagerFactory.<init>(JPAEntityManagerFactory.java:342)
at org.datanucleus.api.jpa.PersistenceProviderImpl.createEntityManagerFactory(PersistenceProviderImpl.java:91)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:152)
... 6 more
Caused by: org.datanucleus.exceptions.NucleusUserException: MetaData handler plugin "persistence" was not found. Please check your CLASSPATH and plugin specification.
    at org.datanucleus.metadata.xml.MetaDataParser.parseMetaDataStream(MetaDataParser.java:263)
... 11 more

我解压了jar，datanucleus-core文件就在那里。我搞不懂发生了什么事。

Answer 1

在更改jar文件时，您不必费心去关注MANIFEST.MF和plugin.xml文件。OSGi的打包允许(基于DataNucleus的)插件机制识别插件和功能。您已经通过玩弄那些jars禁用了它，因此请承担相应的后果。

解决方案:要么按照提供的方式使用jars，要么正确地合并它们(在这种情况下，这是您的责任)