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我正在尝试制作数据核，与 Mongodb 一起工作（使用 JDO）。成功后

mvn clean compile
mvn exec:java

当我第一次运行时它失败了

caused by: org.datanucleus.exceptions.NucleusUserException: Found Meta-Data for class com.samples.jdo.mongodb.Account but this class is either not enhanced or you have multiple copies of jdo-api.jar in your CLASSPATH!! Make sure all persistable classes are enhanced before running DataNucleus and/or the CLASSPATH is correct.

但是如果我再次运行它就可以正常工作，并且我可以看到数据也保存在 mongodb 中。

        // Create a PersistenceManagerFactory for this datastore
    PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory("datanucleus.properties", this.getClass().getClassLoader());
    JDOMetadata jdomd = pmf.newMetadata(); 
    PackageMetadata pmd = jdomd.newPackageMetadata("com.samples.jdo.mongodb");
    ClassMetadata cmd1 = pmd.newClassMetadata(Account.class);
    cmd1.setTable("Account").setIdentityType(javax.jdo.annotations.IdentityType.DATASTORE);
    cmd1.setPersistenceModifier(ClassPersistenceModifier.PERSISTENCE_CAPABLE);

    ClassMetadata cmd2 = pmd.newClassMetadata(Login.class); 
    cmd2.setTable("LOGIN").setIdentityType(javax.jdo.annotations.IdentityType.DATASTORE);
    cmd2.setPersistenceModifier(ClassPersistenceModifier.PERSISTENCE_CAPABLE);


        PersistenceManager pm = pmf.getPersistenceManager();
        Account acct = new Account("firstname","lastname", 3);
        Login login = new Login("flastname", "xxxx");
        acct.setLogin(login);

        final JDOEnhancer enhancer = JDOHelper.getEnhancer(); 
        enhancer.setVerbose(true); 
        enhancer.registerMetadata(jdomd);
        enhancer.setClassLoader(this.getClass().getClassLoader());
        String[] classes = {"com.samples.jdo.mongodb.Account","com.samples.jdo.mongodb.Login" };
        enhancer.addClasses(classes); 
        enhancer.enhance(); 

        pmf.registerMetadata(jdomd);            
        pm.makePersistent(acct);

有任何想法吗？

谢谢

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