播放框架：执行异常

Question

我在Play框架的文档中尝试了演示项目解释。当我尝试创建一个简单的文本框并将其添加到内存数据库时，我遇到了这个错误。

    [error] application - 

! @6pm3lgoh3 - Internal server error, for (POST) [/person] ->

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[CompletionException: java.lang.NullPointerException]]
    at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:269)
    at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:195)
    at play.api.GlobalSettings$class.onError(GlobalSettings.scala:160)
    at play.api.DefaultGlobal$.onError(GlobalSettings.scala:188)
    at play.api.http.GlobalSettingsHttpErrorHandler.onServerError(HttpErrorHandler.scala:98)
    at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:99)
    at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:98)
    at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:344)
    at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:343)
    at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
Caused by: java.util.concurrent.CompletionException: java.lang.NullPointerException
    at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292)
    at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308)
    at java.util.concurrent.CompletableFuture.uniApply(CompletableFuture.java:593)
    at java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:577)
    at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
    at java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:1977)
    at scala.concurrent.java8.FuturesConvertersImpl$CF.apply(FutureConvertersImpl.scala:21)
    at scala.concurrent.java8.FuturesConvertersImpl$CF.apply(FutureConvertersImpl.scala:18)
    at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
    at scala.concurrent.BatchingExecutor$Batch$$anonfun$run$1.processBatch$1(BatchingExecutor.scala:63)
Caused by: java.lang.NullPointerException: null
    at com.avaje.ebean.Model.save(Model.java:208)
    at controllers.HomeController.addPerson(HomeController.java:27)
    at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$4$$anonfun$apply$4.apply(Routes.scala:175)
    at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$4$$anonfun$apply$4.apply(Routes.scala:175)
    at play.core.routing.HandlerInvokerFactory$$anon$4.resultCall(HandlerInvoker.scala:157)
    at play.core.routing.HandlerInvokerFactory$$anon$4.resultCall(HandlerInvoker.scala:156)
    at play.core.routing.HandlerInvokerFactory$JavaActionInvokerFactory$$anon$14$$anon$3$$anon$1.invocation(HandlerInvoker.scala:136)
    at play.core.j.JavaAction$$anon$1.call(JavaAction.scala:73)
    at play.http.HttpRequestHandler$1.call(HttpRequestHandler.java:54)
    at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:108)

控制器类：

public class HomeController extends Controller {

    /**
     * An action that renders an HTML page with a welcome message.
     * The configuration in the <code>routes</code> file means that
     * this method will be called when the application receives a
     * <code>GET</code> request with a path of <code>/</code>.
     */
    public Result index() {
        return ok(index.render("Hello Play Framework (:"));
    }

    public Result addPerson(){
        Person person = Form.form(Person.class).bindFromRequest().get();
        person.save();
        return redirect(routes.HomeController.index());
    }
}

Build.sbt

name := """NewPlay"""

version := "1.0-SNAPSHOT"

lazy val root = (project in file(".")).enablePlugins(PlayJava,PlayEbean)

scalaVersion := "2.11.7"

libraryDependencies ++= Seq(
  javaJdbc,
  cache,
  javaWs
)

Plugins.sbt

// The Play plugin
addSbtPlugin("com.typesafe.play" % "sbt-plugin" % "2.5.1")

// Web plugins
addSbtPlugin("com.typesafe.sbt" % "sbt-coffeescript" % "1.0.0")
addSbtPlugin("com.typesafe.sbt" % "sbt-less" % "1.1.0")
addSbtPlugin("com.typesafe.sbt" % "sbt-jshint" % "1.0.3")
addSbtPlugin("com.typesafe.sbt" % "sbt-rjs" % "1.0.7")
addSbtPlugin("com.typesafe.sbt" % "sbt-digest" % "1.1.0")
addSbtPlugin("com.typesafe.sbt" % "sbt-mocha" % "1.1.0")
addSbtPlugin("org.irundaia.sbt" % "sbt-sassify" % "1.4.2")

// Play enhancer - this automatically generates getters/setters for public fields
// and rewrites accessors of these fields to use the getters/setters. Remove this
// plugin if you prefer not to have this feature, or disable on a per project
// basis using disablePlugins(PlayEnhancer) in your build.sbt
addSbtPlugin("com.typesafe.sbt" % "sbt-play-enhancer" % "1.1.0")

// Play Ebean support, to enable, uncomment this line, and enable in your build.sbt using
// enablePlugins(PlayEbean).
 addSbtPlugin("com.typesafe.sbt" % "sbt-play-ebean" % "1.0.0")

Person.java

package models;
import com.avaje.ebean.Model;
import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Person extends Model {
    @Id
    public String id;
    public String name;
}

AddPerson方法：

public Result addPerson(){
        Person person = Form.form(Person.class).bindFromRequest().get();
        if(person!=null)
            person.save();
        return redirect(routes.HomeController.index());
    }

我可以理解save中的错误。