使用DataNucleus保留用户类型

Question

我正在使用mongodb的datanucleus。我想保留我自己的类型（扩展java.util.Set）但不能。它抛出异常。我该怎么办？

以下是代码：

我的自定义对象是我想要保留的对象的一部分 - CustomSet.java

import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class CustomSet<E> implements Set<E> {
    private final Set<E> hashSet = new HashSet<E>();

    @Override
    public int size() {
        return hashSet.size();
    }

    @Override
    public boolean isEmpty() {
        return hashSet.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
        return hashSet.contains(o);
    }

    @Override
    public Iterator<E> iterator() {
        return hashSet.iterator();
    }

    @Override
    public Object[] toArray() {
        return hashSet.toArray();
    }

    @Override
    public <T> T[] toArray(T[] a) {
        return hashSet.toArray(a);
    }

    @Override
    public boolean add(E e) {
        return hashSet.add(e);
    }

    @Override
    public boolean remove(Object o) {
        return hashSet.remove(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
        return hashSet.containsAll(c);
    }

    @Override
    public boolean addAll(Collection<? extends E> c) {
        return hashSet.addAll(c);
    }

    @Override
    public boolean retainAll(Collection<?> c) {
        return hashSet.retainAll(c);
    }

    @Override
    public boolean removeAll(Collection<?> c) {
        return hashSet.removeAll(c);
    }

    @Override
    public void clear() {
        hashSet.clear();
    }

}

import java.util.Collection; import java.util.HashSet; import java.util.Iterator; import java.util.Set; public class CustomSet<E> implements Set<E> { private final Set<E> hashSet = new HashSet<E>(); @Override public int size() { return hashSet.size(); } @Override public boolean isEmpty() { return hashSet.isEmpty(); } @Override public boolean contains(Object o) { return hashSet.contains(o); } @Override public Iterator<E> iterator() { return hashSet.iterator(); } @Override public Object[] toArray() { return hashSet.toArray(); } @Override public <T> T[] toArray(T[] a) { return hashSet.toArray(a); } @Override public boolean add(E e) { return hashSet.add(e); } @Override public boolean remove(Object o) { return hashSet.remove(o); } @Override public boolean containsAll(Collection<?> c) { return hashSet.containsAll(c); } @Override public boolean addAll(Collection<? extends E> c) { return hashSet.addAll(c); } @Override public boolean retainAll(Collection<?> c) { return hashSet.retainAll(c); } @Override public boolean removeAll(Collection<?> c) { return hashSet.removeAll(c); } @Override public void clear() { hashSet.clear(); } }

我想要保留的My Object - MyDBObject.java

import javax.jdo.annotations.IdGeneratorStrategy;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;

@PersistenceCapable(detachable = "true")
public class MyDBObject {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.UUIDHEX)
    private String id;

    @Persistent
    private String name = null;

    @Persistent
    private CustomSet<String> set = null;

    public MyDBObject(String name, CustomSet<String> set) {
        this.name = name;
        this.set = set;
    }
}

显示问题的测试代码： import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(detachable = "true") public class MyDBObject { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.UUIDHEX) private String id; @Persistent private String name = null; @Persistent private CustomSet<String> set = null; public MyDBObject(String name, CustomSet<String> set) { this.name = name; this.set = set; } }

执行上面的代码后，我收到以下异常：

public class Test {
    private final static PersistenceManagerFactory pmFactory = JDOHelper
            .getPersistenceManagerFactory(new File("appdb.properties"));

    public static void main(String[] args) {
        CustomSet<String> set = new CustomSet<>();
        set.add("Test-1");
        set.add("Test-2");
        set.add("Test-3");
        saveOrUpdate(pmFactory.getPersistenceManager(), new MyDBObject(
                "TestObject", set));
    }

    public static <T> void saveOrUpdate(PersistenceManager pm, T object) {
        Transaction tx = pm.currentTransaction();
        try {
            tx.begin();
            pm.makePersistent(object);
            tx.commit();
        } finally {
            if (tx.isActive()) {
                tx.rollback();
            }
            pm.close();
        }
    }
}

public class Test { private final static PersistenceManagerFactory pmFactory = JDOHelper .getPersistenceManagerFactory(new File("appdb.properties")); public static void main(String[] args) { CustomSet<String> set = new CustomSet<>(); set.add("Test-1"); set.add("Test-2"); set.add("Test-3"); saveOrUpdate(pmFactory.getPersistenceManager(), new MyDBObject( "TestObject", set)); } public static <T> void saveOrUpdate(PersistenceManager pm, T object) { Transaction tx = pm.currentTransaction(); try { tx.begin(); pm.makePersistent(object); tx.commit(); } finally { if (tx.isActive()) { tx.rollback(); } pm.close(); } } }