“The server encountered an error and could not complete your request” on appengine

问题

I am beginner of JAVA and JSP. I am doing semester project on appengine. I have deployed project and there are no compilation or other errors. But when I open my application link it gives an error which is

Error: Server Error
The server encountered an error and could not complete your request.

If the problem persists, please report your problem and mention this error message and the query that caused it.

In my application logs I have seen three types of problems which are

1. /favicon.ico 404 9ms 0kb

   182.177.75.115 - - [19/Dec/2011:05:29:57 -0800] "GET /favicon.ico HTTP/1.1" 404 0 - - "cloudisapp.appspot.com" ms=9 cpu_ms=0 api_cpu_ms=0 cpm_usd=0.000033
   

   No handlers matched this URL.

2. Uncaught exception from servlet

   java.lang.UnsupportedClassVersionError: com/google/mystorage/server/GreetingServiceImpl : Unsupported major.minor version 51.0
   

3. java.lang.UnsupportedClassVersionError: com/google/mystorage/server/GreetingServiceImpl : Unsupported major.minor version 51.0

   This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time. This request may thus take longer and use more CPU than a typical request for your application.

回答1:

The error under 2. means that you are compiling classes under certain JDK version and then trying to run them under the older version of JDK/JRE.

Since AppEngine supports java 5 and 6, I'm guessing that you use Java 7 (OpenJDK)?

Btw, error under 1. is not serious: you are just missing a favicon. See this: http://www.w3.org/2005/10/howto-favicon

回答2:

Check the Admin logs for your project. I had the same issue and in my case was: "Unauthorized sende". Your sender needs to have privilages to send e-mail. In my case just the account owner can do it.

来源：https://stackoverflow.com/questions/8563817/the-server-encountered-an-error-and-could-not-complete-your-request-on-appengi