Вставка бэкэнда GAE не работает

Question

Мой класс сущности

@PersistenceCapable
public class User {

    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
    private Key id;

    @Persistent
    private String userName;

    @Persistent
    private String password;

    public User() {

    }

    public User(String userName, String password) {
        this.userName = userName;

        this.password = password;

    }

    public String getUserName() {
        return userName;

    }

    public void setUserName(String userName) {
        this.userName = userName;

    }

    public String getPassword() {
        return password;

    }

    public void setPassword(String password) {
        this.password = password;

    }

    public Key getId() {
        return id;
    }
}

я сгенерировал класс конечной точки, а затем развернул его в GAE.

Я пошел к исследователю API

https://apis-explorer.appspot.com/apis-explorer/?base=https://ig-project-1280.appspot.com/_ah/api#p/userendpoint/v1/userendpoint.insertUser?_h=4&resource=%257B%250A++%2522password%2522%253A+%2522welcome1%2522%252C%250A++%2522userName%2522%253A+%2522vik.ceo%2540gmail.com%2522%250A%257D&

and did the insert operation. The error come up is:
com.google.api.server.spi.SystemService invokeServiceMethod: exception occurred while calling backend method
java.lang.NullPointerException
    at org.datanucleus.api.jpa.JPAEntityManager.find(JPAEntityManager.java:318)
    at org.datanucleus.api.jpa.JPAEntityManager.find(JPAEntityManager.java:256)
    at photography.viks.app.ig.entity.UserEndpoint.containsUser(UserEndpoint.java:152)
    at photography.viks.app.ig.entity.UserEndpoint.insertUser(UserEndpoint.java:99)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:44)
    at com.google.api.server.spi.SystemService.invokeServiceMethod(SystemService.java:363)
    at com.google.api.server.spi.SystemServiceServlet.execute(SystemServiceServlet.java:113)
    at com.google.api.server.spi.SystemServiceServlet.doPost(SystemServiceServlet.java:71)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    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$CachedChain.doFilter(ServletHandler.java:1166)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444)
    at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:256)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

У тебя есть NullPointerException когда метод UserEndpoint.containsUser(UserEndpoint.java:152) вызывается. Ваше исключение заключено в класс исключений бэкэнд-службы, предоставляемый слоем конечной точки API Google в вашем приложении. Просто проверьте свой код в этом классе, и вы найдете проблему.