Adding API method to App Engine causes NullPointerException

Question

I'm using the local App Engine and I have a working Endpoint, but when I add the following API, the API Explorer (https://developers.google.com/apis-explorer/?base=http://localhost:8888/_ah/api#p/) doesn't load while the JavaScript console has an unhandled exception.

@ApiMethod(name = "getClientByPublicId")
public Client getClientByPublicId(@Named("publicId") String publicId) {
    EntityManager mgr = getEntityManager();
    Client client = null;
    client = mgr.find(Client.class, publicId);
    mgr.close();

    return client;
}

Within the Chrome JavaScript console, it doesn't give anything useful because it's minimized

Uncaught java.lang.NullPointerException
(anonymous function)
(anonymous function)
h
(anonymous function)
F.(anonymous function).z.(anonymous function).z.(anonymous function)
_.T.K.__cb
h
c

The whole API Explorer page comes up blank.

I've ran this in debug mode and set a breakpoint within the added API, but it isn't triggered.

If I load the discovery document at http://localhost:8888/_ah/api/discovery/v1/apis/clientendpoint/v1/rest, it fails with the following response.

{
  "error" : {
    "message" : ""
  }
}

If I remove this new API it all works fine, albeit without having the new API.

Anyone know what is causing this?

Update

I stumbled across Google APis Explorer didn't found my available ApiMethod from my app-engine app and it sounds like there may be a path collision, which I don't understand yet but I'm going to try to work on this idea now.

If this may be the issue, the related API is

@ApiMethod(name = "getClient")
public Client getClient(@Named("id") Long id) {
    EntityManager mgr = getEntityManager();
    Client client = null;
    try {
        client = mgr.find(Client.class, id);
    } finally {
        mgr.close();
    }
    return client;
}

I'll give this a shot and answer my question, unless someone knows different.

Kirk Kirk · Accepted Answer · 2013-06-07T01:21:41

After finding Google APis Explorer didn't found my available ApiMethod from my app-engine app I learned that you must include a new path.

For example, I was able to alter the ApiMethod to

@ApiMethod(
    name = "getClientByPublicId",
    path = "client/publicId/{publicId}",
    httpMethod = "GET"
)

Works great now.

Adding API method to App Engine causes NullPointerException

1 Answers