NullPointerException in JDOPersistenceManager.getObjectById() using DataNucleus 3.0.0-release

问题

I am using DataNucleus 3.0.0-release JDO implementation to connect my Java app to MongoDB.

The related JARs in my CLASSPATH are as follows:

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

The class that I am persisting is as follows:

@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);
    }

    ...
}

And the CustomLocation class:

@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
    }
    ...
}

The code that tries to fetch the object from the DB is as follows:

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

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

The following is the resulting error:

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)

Can anyone spot what the problem is?

Note: I know that DataNucleus 3.1.0-release is available, but I can't use it because of a problem with its enhancer.

UPDATE: I have done some further testing of this issue and it turns out that DataNucleus throws a NullPointerException for those embedded fields that are also marked as being in the defaultFetchGroup and have a value of null.

来源：https://stackoverflow.com/questions/11842527/nullpointerexception-in-jdopersistencemanager-getobjectbyid-using-datanucleus

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java

mongodb

jdo

datanucleus