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我将 JDO 版本 2 数据核与 App Engine SDK 1.7.3 一起使用。我在检索一对多关系中的子对象时遇到问题。

contents = (Collection<ContentType>) persistenceManager.newQuery(ContentType.class).execute();

此查询返回 ContentType 的所有实例，但 ContentType 还包含未从数据库中获取的子“内容”列表。

内容类型.java

public Collection<ContentType> getAllContents() {

        PersistenceManager persistenceManager = PersistenceFactory
                .getInstance().getPersistenceManager();
        Transaction transaction = persistenceManager.currentTransaction();
        Collection<ContentType> contents = null;
        try {
            transaction.begin();
            contents = (Collection<ContentType>) persistenceManager.newQuery(ContentType.class).execute();


            Logging.log("contents in getAllContents=== "+ contents);

            if(contents!=null)
                {
                Logging.log("contents size in getAllContents=== "+ contents.size());

                }

        for (ContentType contentTypeElement : contents) {
            Logging.log("inside main loop in getAllContents, contentTypeElement=== "+ contentTypeElement);
            if(contentTypeElement!=null)
            {
                Logging.log("inside main loop in getAllContents, contentTypeElement having list === "+ contentTypeElement.getContentList());

            }
            if(contentTypeElement.getContentList()!=null)
            {

            for (Content contentElement : contentTypeElement.getContentList()) {
                Logging.log("inside second loop in getAllContents");
                String contentPath = Constants.CONTENT_BASE_URL
                        + contentElement.getContentPath();
                contentElement.setContentPath(contentPath);
            }
            }
            Logging.log("At end of main loop iteration");
        }
        transaction.commit();
        } catch (Exception e) {
            transaction.rollback();
            e.printStackTrace();
            Logging.log("Exception retriving all content, detail in getAllContents: "
                    + e.toString());

        } finally {
            persistenceManager.close();
        }
        return contents;
    }

这是日志

2012-12-14 13:27:14.101
org.datanucleus.TransactionImpl internalPreCommit: >> calling preCommit on org.datanucleus.store.connection.ConnectionManagerImpl$2@873b9f
I 2012-12-14 13:27:14.102
org.datanucleus.TransactionImpl internalPreCommit: >> calling preCommit on org.datanucleus.ObjectManagerImpl@c6b8b0
I 2012-12-14 13:27:14.102
org.datanucleus.TransactionImpl preFlush: >> calling preFlush on org.datanucleus.store.connection.ConnectionManagerImpl$2@873b9f
I 2012-12-14 13:27:14.102
org.datanucleus.TransactionImpl preFlush: >> calling preFlush on org.datanucleus.ObjectManagerImpl@c6b8b0
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: contents in getAllContents=== [com.test.igreetings.persistence.domain.ContentType@14fdb76, com.test.igreetings.persistence.domain.ContentType@1d15a18, com.test.igreetings.persistence.domain.ContentType@171f735, com.test.igreetings.persistence.domain.ContentType@1bf496b]
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: contents size in getAllContents=== 4
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement=== com.test.igreetings.persistence.domain.ContentType@14fdb76
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement having list === null
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: At end of main loop iteration
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement=== com.test.igreetings.persistence.domain.ContentType@1d15a18
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement having list === null
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: At end of main loop iteration
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement=== com.test.igreetings.persistence.domain.ContentType@171f735
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement having list === null
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: At end of main loop iteration
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement=== com.test.igreetings.persistence.domain.ContentType@1bf496b
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: inside main loop in getAllContents, contentTypeElement having list === null
I 2012-12-14 13:27:14.135
com.test.igreetings.util.Logging log: At end of main loop iteration
I 2012-12-14 13:27:14.136
org.datanucleus.TransactionImpl internalPreCommit: >> calling preCommit on org.datanucleus.store.connection.ConnectionManagerImpl$2@66da2c
I 2012-12-14 13:27:14.136
org.datanucleus.TransactionImpl internalPreCommit: >> calling preCommit on org.datanucleus.ObjectManagerImpl@274608

数据核日志

1.  org.datanucleus.store.connection.ConnectionManagerImpl allocateConnection: Connection added to the pool : com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl$DatastoreManagedConnection@74ece8 for key=org.datanucleus.ObjectManagerImpl@107c76b in factory=ConnectionFactory:tx[com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl@119549e]
2.  
3.  D2012-12-14 17:20:11.232
4.  org.datanucleus.store.query.QueryManager getQueryCompilationForQuery: Query "SELECT FROM com.test.igreetings.persistence.domain.ContentType" of language "JDOQL" has been run before so reusing existing generic compilation
5.  D2012-12-14 17:20:11.232
6.  com.google.appengine.datanucleus.query.JDOQLQuery performExecute: JDOQL Query : Executing "SELECT FROM com.test.igreetings.persistence.domain.ContentType" ...
7.  D2012-12-14 17:20:11.233
8.  com.google.appengine.datanucleus.query.JDOQLQuery performExecute: Query compiled as : Kind=com.test.igreetings.persistence.domain.ContentType
9.  D2012-12-14 17:20:11.233
10. com.google.appengine.datanucleus.query.DatastoreQuery executeNormalQuery: Executing query in datastore for SELECT FROM com.test.igreetings.persistence.domain.ContentType
11. D2012-12-14 17:20:11.233
12. org.datanucleus.store.connection.ConnectionManagerImpl allocateConnection: Connection found in the pool : com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl$DatastoreManagedConnection@74ece8 for key=org.datanucleus.ObjectManagerImpl@107c76b in factory=ConnectionFactory:tx[com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl@119549e]
13. D2012-12-14 17:20:11.234
14. com.google.appengine.datanucleus.query.JDOQLQuery performExecute: JDOQL Query : Execution Time = 2 ms
15. D2012-12-14 17:20:11.279
16. org.datanucleus.ObjectManagerImpl getObjectFromLevel1Cache: Object with id "com.test.igreetings.persistence.domain.ContentType:ContentType(3)" not found in Level 1 cache [cache size = 0]
17. D2012-12-14 17:20:11.279
18. org.datanucleus.ObjectManagerImpl putObjectIntoLevel1Cache: Object "com.test.igreetings.persistence.domain.ContentType@165d118" (id="com.test.igreetings.persistence.domain.ContentType:ContentType(3)") added to Level 1 cache (loadedFlags="[NNYNN]")
19. D2012-12-14 17:20:11.279
20. org.datanucleus.state.JDOStateManager wrapSCOField: Object "com.test.igreetings.persistence.domain.ContentType@165d118" (id="com.test.igreetings.persistence.domain.ContentType:ContentType(3)") is having the value in field "endDate" replaced by a SCO wrapper
21. D2012-12-14 17:20:11.280
22. org.datanucleus.state.JDOStateManager wrapSCOField: Object "com.test.igreetings.persistence.domain.ContentType@165d118" (id="com.test.igreetings.persistence.domain.ContentType:ContentType(3)") is having the value in field "startDate" replaced by a SCO wrapper
23. D2012-12-14 17:20:11.280
24. org.datanucleus.ObjectManagerImpl enlistInTransaction: Object "com.test.igreetings.persistence.domain.ContentType@165d118" (id="com.google.appengine.api.datastore.Key:ContentType(3)") enlisted in transactional cache
25. D2012-12-14 17:20:11.280
26. org.datanucleus.ObjectManagerImpl getObjectFromLevel2Cache: Object with id="com.test.igreetings.persistence.domain.ContentType:ContentType(3)" taken from Level 2 cache (fields="[0, 1, 2, 3, 4]", version="") - represented as "com.test.igreetings.persistence.domain.ContentType@165d118"
27. D2012-12-14 17:20:11.280
org.datanucleus.store.connection.ConnectionManagerImpl allocateConnection: Connection found in the pool : com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl$DatastoreManagedConnection@74ece8 for key=org.datanucleus.ObjectManagerImpl@107c76b in factory=ConnectionFactory:tx[com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl@119549e]

因此 contentList 被提取为空，尽管在管理控制台数据查看器中有许多与内容类型相关联的内容实例。我错过了什么？

4

1 回答 1

1

由于您现在说 List 的 ContentType 中没有属性，因此您没有使用 GAE JDO 插件的 v2 保存数据。因此，您不能指望它知道集合中的元素。

解决方案：修复您的数据。

于 2012-12-15T07:25:22.943 回答