如何通过android app更新/修改现有的实体(在谷歌app engine中存储为JSON对象)

I have created an Android app that stores certain information on a Google App Engine. Right now, I can only add information to the GAE using HTTP Post. But if I want to update a property of a value in my entity through the Android app, how would I update the values on the server? I can't figure out how to do that. (If this is vague, ask me to post more about it).I have created an Android app that stores certa