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我正在使用 DataNucleus 3.0.0-release JDO 实现将我的 Java 应用程序连接到 MongoDB。

我的 CLASSPATH 中的相关 JAR 如下：

  • datanucleus-api-jdo-3.0.0-release.jar
  • datanucleus-core-3.0.0-release.jar
  • datanucleus-jdo-query-3.0.0-release.jar
  • datanucleus-mongodb-3.0.0-release.jar
  • mongo-java-driver-2.5.2.jar

我坚持的课程如下：

@PersistenceCapable(detachable = "true")
public class Record implements Serializable, Cacheable<String> {

    private static final long serialVersionUID = 9022509306966814904L;

    @PrimaryKey
    @Persistent(defaultFetchGroup = "true", valueStrategy = IdGeneratorStrategy.IDENTITY)
    private String id;

    @Name
    @Persistent(defaultFetchGroup = "true")
    private String name;

    @Name
    @Persistent(defaultFetchGroup = "true")
    private String surname;

    @Persistent(defaultFetchGroup = "true")
    private Date dateOfBirth;

    @Persistent(defaultFetchGroup = "true")
    private Date dateRecorded;

    @Persistent(defaultFetchGroup = "true")
    private String locationId;

    @Persistent(embedded = "true", defaultFetchGroup = "true")
    private CustomLocation customLocation;

    @Persistent(defaultFetchGroup = "true")
    private Category category;

    @Persistent(embedded = "true", defaultFetchGroup = "true")
    private CustomCategory customCategory;

    @Persistent(defaultFetchGroup = "true")
    private String description;

    @Persistent(embeddedElement = "true", defaultFetchGroup = "true")
    private List<StoredImageInfo> images;

    @Persistent(embeddedElement = "true", defaultFetchGroup = "true")
    private List<StoredAudioInfo> audio;

    @Persistent(embeddedElement = "true", defaultFetchGroup = "true")
    private List<StoredFileInfo> files;

    @Persistent(defaultFetchGroup = "true")
    private ModerationMode moderationMode;

    @Persistent(defaultFetchGroup = "true")
    private VisibilityMode visibilityMode;

    @Persistent(embedded = "true", defaultFetchGroup = "true")
    private UserProfileSummary owner;

    @Persistent(embeddedElement = "true", defaultFetchGroup = "true")
    private Map<String, UserProfileSummary> editors;

    @Persistent(embeddedElement = "true", defaultFetchGroup = "true")
    private Map<String, UserProfileSummary> connections;

    @Persistent(embeddedElement = "true", defaultFetchGroup = "true")
    private Map<String, RecordSummary> recordConnections;

    @Persistent(defaultFetchGroup = "true")
    private RecordType type;

    @Persistent(defaultFetchGroup = "true")
    private Date expiry;

    public Record() {
    }

    public Record(Record copy) {
    deepCopy(copy);
    }

    ...
}

和CustomLocation班级：

@PersistenceCapable(embeddedOnly="true")
public class CustomLocation implements Serializable {

    private static final long serialVersionUID = -7754029273366194129L;

    @PrimaryKey
    @Persistent(defaultFetchGroup = "true", valueStrategy = IdGeneratorStrategy.IDENTITY)
    private String id;

    @Persistent(defaultFetchGroup = "true")
    private String city;

    @Persistent(defaultFetchGroup = "true")
    private String countryKey;

    @Persistent(defaultFetchGroup = "true")
    private String locale;

    @SuppressWarnings("unused")
    private CustomLocation() {
        // for serialization
    }
    ...
}

尝试从数据库中获取对象的代码如下：

PersistenceManager pm = MyPersistenceManagerFactory.get().getPersistenceManager();

Record record = null;
try {
    record = pm.getObjectById(Record.class, recordId);
}
catch (JDOObjectNotFoundException onfe) {
    // handle
}
catch (Exception e) {
    // handle
}

以下是产生的错误：

java.lang.NullPointerException
    at org.datanucleus.store.mongodb.fieldmanager.FetchFieldManager.fetchStringField(FetchFieldManager.java:243)
    at org.datanucleus.state.AbstractStateManager.replacingStringField(AbstractStateManager.java:2165)
    at com.myproject.location.domain.CustomLocation.jdoReplaceField(CustomLocation.java)
    at com.myproject.location.domain.CustomLocation.jdoReplaceFields(CustomLocation.java)
    at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:1989)
    at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2009)
    at org.datanucleus.store.mongodb.fieldmanager.FetchFieldManager.fetchObjectField(FetchFieldManager.java:353)
    at org.datanucleus.state.AbstractStateManager.replacingObjectField(AbstractStateManager.java:2182)
    at com.myproject.domain.Record.jdoReplaceField(Record.java)
    at com.myproject.domain.Record.jdoReplaceFields(Record.java)
    at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:1989)
    at org.datanucleus.state.JDOStateManagerImpl.replaceFields(JDOStateManagerImpl.java:2009)
    at org.datanucleus.store.mongodb.MongoDBPersistenceHandler.fetchObject(MongoDBPersistenceHandler.java:600)
    at org.datanucleus.state.JDOStateManagerImpl.loadFieldsFromDatastore(JDOStateManagerImpl.java:1696)
    at org.datanucleus.state.JDOStateManagerImpl.validate(JDOStateManagerImpl.java:3576)
    at org.datanucleus.ObjectManagerImpl.findObject(ObjectManagerImpl.java:3246)
    at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectById(JDOPersistenceManager.java:1731)
    at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectById(JDOPersistenceManager.java:1749)
    at com.myproject.server.GetRecordHandler.execute(GetRecordHandler.java:37)

谁能发现问题所在？

注意：我知道 DataNucleus 3.1.0-release 可用，但我不能使用它，因为它的增强器有问题。

更新：我对这个问题做了一些进一步的测试，结果发现 DataNucleusNullPointerException为那些embedded也被标记为在 中defaultFetchGroup并且值为null.

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