GAE：比较执行JDO查询时返回错误结果的字符串值 [英] GAE: Comparing String value returning false results when executing JDO query

问题描述

对于iOS项目，我使用GAE（Java堆栈）来存储用户的设备令牌并使用它发送推送通知。

我有一个Device实体其中包含几个字段，包括String类型的appVersion字段。数据库包含一些版本为1的设备，一些版本为2。

当我运行一个JDO查询来查找所有具有appVersion的设备等于2时，结果，但是当我对版本1执行相同的操作时，查询不返回任何结果，尽管实体符合此条件。

这是代码：

  javax.jdo.Query query = _pm.newQuery（Device.class，appVersion == appVersionParams）; 
 
 query.declareParameters（String.class.getName（）+appVersionParams）; 
 
列表<设备> results =（List< Device>）query.execute（message.getAppVersion（））; 
  

我多次验证版本1的设备实体存储正确（类型是String并包含正确的修剪值确实与我传递的参数完全匹配）。

我首先在开发环境中遇到过这个问题，所以我删除了本地数据库并且创建测试实体并再次运行查询 - 这次它返回了版本1和2的预期结果。但是，在我重新启动服务器之后，它又返回了版本1的错误结果（虽然版本2有效）。希望这只是本地开发环境中的一个bug。我将它部署到生产环境，它只返回4个实体（有几千个匹配这个条件） - 所有实体都以相同的方式/ API存储。

I也尝试从JDO切换到低级API来获取实体，但我得到了相同的奇怪行为。这是它的代码：

 查询q =新的查询（设备）; 
 q.addFilter（appVersion，FilterOperator.EQUAL，message.getAppVersion（））; 
  

我会在这里疯狂。发生了什么事？

解决方案

这个问题与我对持久化实体结构/模式所做的修改没有正确使用 serialVersionUID 。查看问题的更多细节的评论，特别是Viruzzo的。

For an iOS project I'm using GAE (Java stack) to store the user's device token and use it to send Push notifications.

I have a Device entity which contains several fields, including "appVersion" field of type String. The database contains some Devices with version 1 and some with version 2.

When I run a JDO query to find all devices with "appVersion" equals to 2 it returns the expected result, but when I do the same with version 1 the query return no result, although there are Entities which match this condition.

This is the code:

javax.jdo.Query query = _pm.newQuery(Device.class, "appVersion == appVersionParams");

query.declareParameters(String.class.getName()+" appVersionParams");

List<Device> results = (List<Device>) query.execute(message.getAppVersion());

I verified several times that the Device Entities with version 1 are stored correctly (the type is String and contains the right, trimmed value which indeed match exactly to the parameter I'm passing).

I first encountered this issue on the Dev environment, so I deleted the local DB and created test entities and run the Query again - this time it returned the expected results for version 1 and 2. But after I restarted the server it again returned false results for version 1 (while doing good with version 2). Hoping it was just a bug on the local dev env. I deployed it to the production environment and it returned only 4 entities (there are few thousands match this condition) - all entities were stored in the same way/API.

I also tried to switch from JDO to the low level APIs to fetch the Entities but i got the same weird behavior. This is the code for it:

Query q = new Query("Device");
q.addFilter("appVersion", FilterOperator.EQUAL, message.getAppVersion());

I'm going nuts here.. what's going on ??

解决方案

The problem was related to a modification I made to the persistent Entity structure/schema without proper use of serialVersionUID. See the question's comments for more details, specifically Viruzzo's one.

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