java - 在 Google App Engine 中使用 JDO 定义的集合中保留任意顺序

Question

我正在将我的代码迁移到 Java7 和最新的 Datanucleus App Engine 插件，但我遇到了顺序问题。

我有一个祖先类，它拥有一些需要维护用户定义的特定顺序的子类。所以我使用了没有任何@Extension 的@Order 注释。 使用以前的 JDO 版本一切正常，现在我的单元测试失败了，因为它不再找到这个 _INTEGER_IDX 属性。

我按照此文档创建了一个简单的测试项目 Owned one-to-many relationship为了从一个新的例子开始但它仍然不起作用: GitHub-project .

我在这里总结了这个模型:

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Book {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true")
    private String key = null;

    @Persistent
    private String title = null;

    @Persistent(mappedBy="book")
    @Order
    private List<Chapter> chapters = null;

..和..

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Chapter {
    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    @Extension(vendorName="datanucleus", key="gae.encoded-pk", value="true")
    private String key = null;

    @Persistent
    private String name = null;

    @Persistent
    private Book book = null;

.. 这是失败的单元测试:

@Test
public void testJdoDependingEntities() throws EntityNotFoundException {
    PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory("transactions-optional");

    PersistenceManager pm = pmf.getPersistenceManager();

    Book bookJdo = null;

    try {
        pm.currentTransaction().begin();

        bookJdo = new Book("myTitle");
        Chapter cpt1 = new Chapter("myname1");
        Chapter cpt2 = new Chapter("myname2");
        Chapter cpt3 = new Chapter("myname3");
        Chapter cpt4 = new Chapter("myname4");
        Chapter cpt5 = new Chapter("myname5");
        Chapter cpt6 = new Chapter("myname6");

        bookJdo.getChapters().add(cpt1);
        cpt1.setBook(bookJdo);
        bookJdo.getChapters().add(cpt2);
        cpt2.setBook(bookJdo);
        bookJdo.getChapters().add(cpt3);
        cpt3.setBook(bookJdo);
        bookJdo.getChapters().add(cpt4);
        cpt4.setBook(bookJdo);
        bookJdo.getChapters().add(cpt5);
        cpt5.setBook(bookJdo);
        bookJdo.getChapters().add(cpt6);
        cpt6.setBook(bookJdo);

        pm.makePersistent(bookJdo);

        pm.currentTransaction().commit();
    } catch(Exception e) {
        e.printStackTrace();
    }
    finally {
        if(pm.currentTransaction().isActive()) {
            pm.currentTransaction().rollback();
        }
        pm.close();
    }

    Entity book = datastore.get(KeyFactory.stringToKey(bookJdo.getKey()));
    assertEquals("myTitle", book.getProperty("title"));

    Query query = new com.google.appengine.api.datastore.Query(
            "Chapter",
            KeyFactory.stringToKey(bookJdo.getKey()));
    FetchOptions options = FetchOptions.Builder.withDefaults();

    QueryResultList<Entity> resultEntity = datastore.prepare(query)
            .asQueryResultList(options);

    assertEquals(6, resultEntity.size());

    // print values
    System.out.println("From ancestor query:");
    System.out.println("All the props: "+resultEntity.get(0).getProperties());
    System.out.println("idx prop: "+resultEntity.get(0).getProperty("chapters_INTEGER_IDX"));
    System.out.println();

    Entity chapter = datastore.get(resultEntity.get(0).getKey());
    System.out.println("All the props: "+chapter.getProperties());
    System.out.println("idx prop: "+chapter.getProperty("chapters_INTEGER_IDX"));

    // test against JUnit
    assertNotNull(resultEntity.get(0).getProperty("chapters_INTEGER_IDX"));
    assertNotNull(chapter.getProperty("chapters_INTEGER_IDX"));
 }

这是 GitHub-project .

Answer 1

为什么“Chapter.book”上有一个 mappedBy？那是非法的。如果关系是双向的，那么它在没有 FK 的一侧有一个 mappedBy。