[英]Google App Engine (Java) App stopped working (all versions)
[英]JPA delete all not working on Google app engine
我有以下代码,并试图删除所有类别,但是这使我抛出非法参数异常。 我正在使用Google App Engine。
public void deleteCategories() {
EntityManager em = EMFService.get().createEntityManager();
try {
em.getTransaction().begin();
Query q = em.createQuery("DELETE FROM Category cat");
q.executeUpdate();
em.getTransaction().commit();
System.out.println("All records are deleted.");
} catch(Exception ex){
System.out.println(ex.toString());
}
finally {
if (em.getTransaction().isActive()) {
em.getTransaction().rollback();
}
}
}
运行此代码后,我得到javax.persistence.PersistenceException:非法参数,完整的堆栈跟踪如下:原因:java.lang.IllegalArgumentException:需要明确指定跨组事务,请参见TransactionOptions.Builder.withXGfound两个元素{类型:“类别”名称:“ 1”}和元素{类型:“类别”名称:“ 100223”}
at com.google.appengine.api.datastore.DatastoreApiHelper.translateError(DatastoreApiHelper.java:39)
at com.google.appengine.api.datastore.DatastoreApiHelper$1.convertException(DatastoreApiHelper.java:76)
at com.google.appengine.api.utils.FutureWrapper.get(FutureWrapper.java:94)
at com.google.appengine.api.datastore.AsyncDatastoreServiceImpl$10.get(AsyncDatastoreServiceImpl.java:622)
at com.google.appengine.api.datastore.AsyncDatastoreServiceImpl$10.get(AsyncDatastoreServiceImpl.java:618)
at com.google.appengine.api.datastore.FutureHelper$TxnAwareFuture.get(FutureHelper.java:171)
at com.google.appengine.api.datastore.FutureHelper.getInternal(FutureHelper.java:71)
at com.google.appengine.api.datastore.FutureHelper.quietGet(FutureHelper.java:32)
at com.google.appengine.api.datastore.DatastoreServiceImpl.delete(DatastoreServiceImpl.java:128)
at com.google.appengine.datanucleus.WrappedDatastoreService.delete(WrappedDatastoreService.java:184)
at com.google.appengine.datanucleus.query.DatastoreQuery.wrapEntityQueryResult(DatastoreQuery.java:417)
at com.google.appengine.datanucleus.query.DatastoreQuery.performExecute(DatastoreQuery.java:343)
at com.google.appengine.datanucleus.query.JPQLQuery.performExecute(JPQLQuery.java:176)
at org.datanucleus.store.query.Query.executeQuery(Query.java:1789)
at org.datanucleus.store.query.Query.executeWithMap(Query.java:1693)
at org.datanucleus.api.jpa.JPAQuery.executeUpdate(JPAQuery.java:124)
... 28 more
delete
语句中无需使用别名,因此您可以从JPQL中删除cat
。 catch
块部分中回滚事务。 EntityManager
后,应始终关闭它,通常在finally
块中。 这是代码的样子
public void deleteCategories() {
EntityManager em = EMFService.get().createEntityManager();
try {
em.getTransaction().begin();
Query q = em.createQuery("DELETE FROM Category");
q.executeUpdate();
em.getTransaction().commit();
System.out.println("All records are deleted.");
} catch(Exception ex){
if (em.getTransaction().isActive()) {
em.getTransaction().rollback();
}
//should be changed for something like
//log.error("Error while deleting all the categories", ex);
ex.printStacktrace(System.out);
} finally {
em.close();
}
}
猫在您的查询中做什么? 我猜这是错误,因为删除行的常规查询模式如下,因此无需使用别名:
删除*来自mytablename
要么
从mytablename删除
也许您可以在已经回答的问题中进一步检查-> 使用JPA从表中删除所有行
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