播放2.4 Finder引发Null指针异常

Question

I'm currently having an issue with a Finder instance in Play 2.4 whereby it returns a null pointer exception when used. Here is the code trying to use it

public ExpressionList<ClientAuthorization> getAuthorizationQuery(String appId) {
        return ClientAuthorization.find.where().eq("app_id", appId).eq("active", 1);
    }

And the model class

package models;

import com.avaje.ebean.Model;

import javax.persistence.*;
import java.sql.Timestamp;


@Entity
@Table(name="client_authorization")
public class ClientAuthorization extends Model {

    public static final Finder<Long, ClientAuthorization> find = new Finder<>(ClientAuthorization.class);


    @Id
    public long clientAuthorizationId;

    @Column(nullable=false, length=45)
    public String appId;

    @Column(nullable=false, length=45)
    public String apiKey;

    @Column(nullable=false)
    public boolean active;

    @Column(nullable = false)
    public boolean isAdmin;

    @Column(nullable=false)
    public Timestamp createdDate;

    @Column(nullable=false)
    public Timestamp updatedDate;

    @PrePersist
    protected void createdAt() {
        this.createdDate = new Timestamp(System.currentTimeMillis());
        this.updatedDate = new Timestamp(System.currentTimeMillis());
    }

    @PostPersist
    protected void updatedAt() {
        this.updatedDate = new Timestamp(System.currentTimeMillis());
    }


}

This works fine for every model I've ever created in Play, so I'm not sure what's going on. Here is what I get

I greatly appreciate any help I can get. This is driving me crazy in an upgrade project I'm working on. The last upgrade I did went just fine, but this one is giving me problems.

Additional info: It fails on the call to where() just after the ClientAuthorization static call to find

update

Since it came up in a comment, this is not just a question of what a NPE is, I know that already. For some reason the finder is not initialized. However, looking at this model, and every model I've ever written, there is no reason for this to be happening.

Here is the stack trace

@6o9455j27 - Internal server error, for (GET) [/] ->

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[NullPointerException: null]]
    at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:265) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:191) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.GlobalSettings$class.onError(GlobalSettings.scala:179) [play_2.11-2.4.4.jar:2.4.4]
    at play.api.DefaultGlobal$.onError(GlobalSettings.scala:212) [play_2.11-2.4.4.jar:2.4.4]
    at play.api.http.GlobalSettingsHttpErrorHandler.onServerError(HttpErrorHandler.scala:94) [play_2.11-2.4.4.jar:2.4.4]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$9$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:151) [play-netty-server_2.11-2.4.4.jar:2.4.4]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$9$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:148) [play-netty-server_2.11-2.4.4.jar:2.4.4]
    at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:36) [scala-library-2.11.6.jar:na]
    at scala.util.Failure$$anonfun$recover$1.apply(Try.scala:215) [scala-library-2.11.6.jar:na]
    at scala.util.Try$.apply(Try.scala:191) [scala-library-2.11.6.jar:na]
    at scala.util.Failure.recover(Try.scala:215) [scala-library-2.11.6.jar:na]
    at scala.concurrent.Future$$anonfun$recover$1.apply(Future.scala:324) [scala-library-2.11.6.jar:na]
    at scala.concurrent.Future$$anonfun$recover$1.apply(Future.scala:324) [scala-library-2.11.6.jar:na]
    at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32) [scala-library-2.11.6.jar:na]
    at play.api.libs.iteratee.Execution$trampoline$.executeScheduled(Execution.scala:109) [play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:71) [play-iteratees_2.11-2.4.4.jar:2.4.4]
    at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40) [scala-library-2.11.6.jar:na]
    at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:248) [scala-library-2.11.6.jar:na]
    at scala.concurrent.Promise$class.complete(Promise.scala:55) [scala-library-2.11.6.jar:na]
    at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:153) [scala-library-2.11.6.jar:na]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:23) [scala-library-2.11.6.jar:na]
    at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40) [akka-actor_2.11-2.3.13.jar:na]
    at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397) [akka-actor_2.11-2.3.13.jar:na]
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) [scala-library-2.11.6.jar:na]
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) [scala-library-2.11.6.jar:na]
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) [scala-library-2.11.6.jar:na]
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) [scala-library-2.11.6.jar:na]
Caused by: java.lang.NullPointerException: null
    at com.avaje.ebean.Model$Find.query(Model.java:547) ~[avaje-ebeanorm-4.6.2.jar:na]
    at com.avaje.ebean.Model$Find.where(Model.java:741) ~[avaje-ebeanorm-4.6.2.jar:na]
    at repositories.AuthRepository.getAuthorizationQuery(AuthRepository.java:12) ~[classes/:na]
    at interceptors.AuthInterceptor.call(AuthInterceptor.java:31) ~[classes/:na]
    at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:94) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:94) ~[play_2.11-2.4.4.jar:2.4.4]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library-2.11.6.jar:na]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library-2.11.6.jar:na]
    at play.core.j.HttpExecutionContext$$anon$2.run(HttpExecutionContext.scala:40) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:70) [play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.core.j.HttpExecutionContext.execute(HttpExecutionContext.scala:32) ~[play_2.11-2.4.4.jar:2.4.4]
    at scala.concurrent.impl.Future$.apply(Future.scala:31) ~[scala-library-2.11.6.jar:na]
    at scala.concurrent.Future$.apply(Future.scala:492) ~[scala-library-2.11.6.jar:na]
    at play.core.j.JavaAction.apply(JavaAction.scala:94) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.utils.Threads$.withContextClassLoader(Threads.scala:21) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:104) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:103) ~[play_2.11-2.4.4.jar:2.4.4]
    at scala.Option.map(Option.scala:146) ~[scala-library-2.11.6.jar:na]
    at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:103) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:96) ~[play_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:524) ~[play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:524) ~[play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:560) ~[play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:560) ~[play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:536) ~[play-iteratees_2.11-2.4.4.jar:2.4.4]
    at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:536) ~[play-iteratees_2.11-2.4.4.jar:2.4.4]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library-2.11.6.jar:na]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library-2.11.6.jar:na]
    ... 6 common frames omitted

Answer 1

In case somebody runs into a similar problem, the config should be double-checked . The default Model superclass does not care of it. Details about aplication.conf and orm.xml can be found here:

EBean config

Answer 2

创建静态Finder时指定服务器名称对我有用

Finder<String, Site> find = new Finder<String, Site>([servername], Site.class);

Answer 3

I think you need to use com.avaje.ebean.Model.Find instead of Model.Finder class.

 public static final Find<Long,ClientAuthorization> find = new Find<Long,ClientAuthorization>(){};

Alternatively, you can use play.db.ebean.Model.Finder

public static Finder<Long,ClientAuthorization> find = new Finder<Long,ClientAuthorization>(  Long.class, ClientAuthorization.class ); 

I have not tested, please check and let me know. Please post the Exception trace for better understanding.

Answer 4

Looking through the source code a bit suggests that having a staticly initialized find object within the same class that you are building the find object for might be a bad idea. I would:

• first completey remove this variable from the model class and create that field somewhere else.
• or (if you must have it there) initialize that object lazily when it is first requested.

I have had a very mind-boggling issue some time ago with a static field referencing the encompassing class type and producing unexpected behaviour.