GCM: java.lang.NoClassDefFoundError: com/google/android/gcm/server/Sender

问题

I have been trying to get Google Cloud Messaging to work in eclipse. I was able to compile the example given on their demo webpage and run that without any errors; however, when I try to create my own example using jersey I get the run time error "java.lang.NoClassDefFoundError: com/google/android/gcm/server/Sender" when the following code tries to create a sender.

@POST
@Path("/send")
public Response sendMessage() throws IOException
{
    Sender sender = new Sender("api_key");
    Message message = new Message.Builder().build();
    sender.send(message, DataStore.getDevices(), 5);
    return Response.status(200).entity("Success").build();
}

Note: I have replaced my real api key with api_key. I know it works because I was able to get the demo working by running the ant commands explained in the tutorial. Also just to be specific in case of ambiguity, the error I am getting is server side, and has nothing to do with the android device.

Things I have already tried:

1. I have included the gcm-server.jar in my WEB-INF/lib folder and under project properties I have included it in the build path.
2. I have also tried, as mentioned on other sites, to include json_simple-1.1.jar the same way I included gcm-server.jar. I don't see how this would effect this error but I saw this listed as an answer in a few different places.
3. (Solution) Deleted the tomcat server and created a new one. I probably could have just cleaned the project instead and had the same results.

Demo tutorial link: http://developer.android.com/guide/google/gcm/demo.html.

回答1:

I just found a solution to my problem. In frustration I deleted the old Tomcat server from eclipse and created a new one. When I ran the project again there weren't any problems at all. When I first set up the project I had included the jar files in WEB-INF/lib and later, after reading a lot of posts on the internet, added gcm-server.jar to the build path. It appears that this action would have fixed it but for some reason unknown to me there were some left over files on the server from before the change. I should have tried cleaning my project but I didn't even think about that being the issue. Anyway, I hope that this helps someone because I've sort of condensed all of the information I could find on the internet into this post, as well as included my own dilemma and solution to it.

来源：https://stackoverflow.com/questions/13355446/gcm-java-lang-noclassdeffounderror-com-google-android-gcm-server-sender