为什么谷歌应用引擎抛出持久性异常

I am writing a web application using java on the Google app engine. Everything was working ok cause I had deployed and run the application numerous times. After I updated my jdk 7 to update 6 (had a lower version of jdk 7) and deployed it I started getting a 500 Http response code (internal server error). When I check the logs a:I am writing a web application using java on th