如何在发布请求-Google Cloud Endpoints中修复NullPointerException？

Question

I am trying to create an api method on google endpoint where I am receiving the data in the request body which I want save in the datastore.

However, I get the following response when I make a request:

{
    "error": {
        "errors": [
            {
                "domain": "global",
                "reason": "backendError",
                "message": "java.lang.NullPointerException"
            }
        ],
        "code": 503,
        "message": "java.lang.NullPointerException"
    }
}

Please refer the api method below:

@ApiMethod(name="profile",
               path="profile",
               httpMethod=HttpMethod.POST)
    public UserProfile addUser(UserProfile userProfile) {

        userProfileService.addUser(userProfile);
        return userProfile;
    }

Below is my dao class implementation:

package com.travelplannr.endpoint.dao;

import com.googlecode.objectify.Objectify;
import com.googlecode.objectify.ObjectifyFactory;
import com.googlecode.objectify.ObjectifyService;
import com.travelplannr.endpoint.entities.UserProfile;

public class UserProfileDaoImpl implements UserProfileDao {

    static {
        factory().register(UserProfile.class);
    }

    public static Objectify ofy() {
        return ObjectifyService.ofy();
    }

    public static ObjectifyFactory factory() {
        return ObjectifyService.factory();
    }

    @Override
    public void addUser(UserProfile userProfile) {

        UserProfileDaoImpl.ofy().save().entity(userProfile).now();
    }

}

Please refer Entity class below:

package com.travelplannr.endpoint.entities;

import com.googlecode.objectify.annotation.Entity;
import com.googlecode.objectify.annotation.Id;

@Entity
public class UserProfile {

    @Id
    private String email;
    private String name;
    private String password;

    public UserProfile() {}

    public UserProfile(String name, String email, String password) {
        this.name = name;
        this.email = email;
        this.password = password;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "UserProfile [name=" + name + ", email=" + email + ", password=" + password + "]";
    }
}

Below is the stack trace:

java.lang.NullPointerException
    at com.travelplannr.endpoint.api.TravelPlannrApi.addUser(TravelPlannrApi.java:34)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:129)
    at com.google.api.server.spi.SystemService.invokeServiceMethod(SystemService.java:351)
    at com.google.api.server.spi.handlers.EndpointsMethodHandler$RestHandler.handle(EndpointsMethodHandler.java:119)
    at com.google.api.server.spi.handlers.EndpointsMethodHandler$RestHandler.handle(EndpointsMethodHandler.java:102)
    at com.google.api.server.spi.dispatcher.PathDispatcher.dispatch(PathDispatcher.java:49)
    at com.google.api.server.spi.EndpointsServlet.service(EndpointsServlet.java:71)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:72)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:134)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:48)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:122)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.DevAppServerRequestLogFilter.doFilter(DevAppServerRequestLogFilter.java:44)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:95)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:508)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

I have also checked removing the call to UserProfileService.add in the api method and just returning the object that I receive in the request body and it is not empty.

Please help! Thanks in advance.

Answer 1

The context missing from your post is how userProfileService is initialized or expected to get set in the first place (which is outside the scope of this ApiMethod). If I'm understanding correctly, this doesn't seem like an issue with Endpoints at all; that's just a red herring.

It may help speed up your debugging by temporarily removing the Endpoints integration and making sure all of your object references are being created correctly by whatever injection framework/method you're using to wire things up. Maybe create a small main() method that triggers your object bootstrapping and checks to ensure this userProfileService is non-null? That would allow you to iterate much faster in a command-line environment until you figure out the root cause of the initialization failure before you try to get Endpoints integration working.