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我正在使用Java 1.7.0_15和2.10.0來玩play 2.1.1 Scala。
錯誤（[NullPointerException: null]）當我試圖以HashMap的身份訪問ArrayList的內容時，我都跳轉。PlayFramework [NullPointerException：null]在ArrayList或HashMap中添加項目時
我已經試過了兩種方式：
首先，在構造函數初始化屬性：
import java.util.ArrayList;
import java.util.HashMap;
public Class User extends Model {
...
public User(...) {
...
countriesVisited = new ArrayList<Country>();
travels = new HashMap<Country, List<Car>>();
}
....
}
類Country和Car，只有一個String屬性。
但是，隨着用戶使用的形式發佈：
public static Result create() {
Form<User> formUser = form(User.class);
return ok(createUSer.render(formUser));
}
public static Result save() {
Form<User> formUSer = form(User.class)
.bindFromRequest();
if (formUser.hasErrors()) {
return badRequest(createUser.render(formUser));
}
User u = formUser.get();
u.save();
return redirect(routes.Application.index());
}
我決定取消的構造，因爲沒有使用，並初始化ArrayList中的HashMap在屬性的聲明：
public Class User extends Model {
List<Country> countriesVisited = new ArrayList<Country>();
Map <Country, List<Car>> travels = new HashMap<Country, List<Car>>();
...
}
兩者當訪問的內容顯示在一個視圖給我NullPointerException: null
public static Result getCountriesVisited() {
User u = User.find.byId(request().username());
ArrayList<Country> countries = Country.find.all();
return ok(showCountriesVisited.render(u.countriesVisited, countries));
}
而且showCountriesVisited.scala.html：
@(countriesVisited: List[Country], countries : List[Country])
@import helper._
@import helper.twitterBootstrap
@main("Mark all the countries visited"){
@form(routes.AdminUser.updateCountries()){
@for(cv <- countries){
@if(countriesVisited.contains(cv)){ //THE ERROR ALWAYS SHOWS ME THIS LINE
<input type='checkbox' name='countriesVisited' [email protected]
checked="yes">@cv.name<br>
} else {
<input type='checkbox' name='countriesVisited' [email protected]>@cv.name<br>
}
}
<input type="submit" value="Save">
}
}
HashMap我同樣的事情發生。
在此先感謝。
這裏堆棧跟蹤： ！ @ 6fbjmmpaa - 內部服務器錯誤，爲（GET）[/ UserTravel] - >
play.api.Application$$anon$1: Execution exception[[NullPointerException: null]]
at play.api.Application$class.handleError(Application.scala:289) ~[play_2.10.jar:2.1.1]
at play.api.DefaultApplication.handleError(Application.scala:383) [play_2.10.jar:2.1.1]
at play.core.server.netty.PlayDefaultUpstreamHandler$$anon$2$$anonfun$handle$1.apply(PlayDefaultUpstreamHandler.scala:144) [play_2.10.jar:2.1.1]
at play.core.server.netty.PlayDefaultUpstreamHandler$$anon$2$$anonfun$handle$1.apply(PlayDefaultUpstreamHandler.scala:140) [play_2.10.jar:2.1.1]
at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) [play_2.10.jar:2.1.1]
at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) [play_2.10.jar:2.1.1]
at play.api.libs.concurrent.PlayPromise$$anonfun$extend$1$$anonfun$apply$1.apply(Promise.scala:104) [play_2.10.jar:2.1.1]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library.jar:na]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library.jar:na]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [na:1.7.0_15]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.7.0_15]
at java.lang.Thread.run(Unknown Source) [na:1.7.0_15]
java.lang.NullPointerException: null
at views.html.showCountriesVisited$$anonfun$apply$1$$anonfun$apply$2$$anonfun$apply$3.apply(showCountriesVisited.template.scala:39) ~[na:na]
at views.html.showCountriesVisited$$anonfun$apply$1$$anonfun$apply$2$$anonfun$apply$3.apply(showCountriesVisited.template.scala:38) ~[na:na]
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244) ~[scala-library.jar:na]
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244) ~[scala-library.jar:na]
at scala.collection.Iterator$class.foreach(Iterator.scala:727) ~[scala-library.jar:na]
at scala.collection.AbstractIterator.foreach(Iterator.scala:1156) ~[scala-library.jar:na]
at scala.collection.IterableLike$class.foreach(IterableLike.scala:72) ~[scala-library.jar:na]
at scala.collection.AbstractIterable.foreach(Iterable.scala:54) ~[scala-library.jar:na]
at scala.collection.TraversableLike$class.map(TraversableLike.scala:244) ~[scala-library.jar:na]
at scala.collection.AbstractTraversable.map(Traversable.scala:105) ~[scala-library.jar:na]
at views.html.showCountriesVisited$$anonfun$apply$1$$anonfun$apply$2.apply(showCountriesVisited.template.scala:38) ~[na:na]
at views.html.showCountriesVisited$$anonfun$apply$1$$anonfun$apply$2.apply(showCountriesVisited.template.scala:36) ~[na:na]
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244) ~[scala-library.jar:na]
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244) ~[scala-library.jar:na]
at scala.collection.Iterator$class.foreach(Iterator.scala:727) ~[scala-library.jar:na]
at scala.collection.AbstractIterator.foreach(Iterator.scala:1156) ~[scala-library.jar:na]
at scala.collection.IterableLike$class.foreach(IterableLike.scala:72) ~[scala-library.jar:na]
at scala.collection.AbstractIterable.foreach(Iterable.scala:54) ~[scala-library.jar:na]
at scala.collection.TraversableLike$class.map(TraversableLike.scala:244) ~[scala-library.jar:na]
at scala.collection.AbstractTraversable.map(Traversable.scala:105) ~[scala-library.jar:na]
at views.html.showCountriesVisited$$anonfun$apply$1.apply(showCountriesVisited.template.scala:36) ~[na:na]
at views.html.showCountriesVisited$$anonfun$apply$1.apply(showCountriesVisited.template.scala:34) ~[na:na]
at views.html.helper.form$.apply(form.template.scala:45) ~[play_2.10.jar:2.1.1]
at views.html.showCountriesVisited$.apply(showCountriesVisited.template.scala:34) ~[na:na]
at views.html.showCountriesVisited$.render(showCountriesVisited.template.scala:58) ~[na:na]
at views.html.showCountriesVisited.render(showCountriesVisited.template.scala) ~[na:na]
at controllers.User.getCountriesVisited(User.java:69) ~[na:na]
at Routes$$anonfun$routes$1$$anonfun$applyOrElse$15$$anonfun$apply$15.apply(routes_routing.scala:258) ~[na:na]
at Routes$$anonfun$routes$1$$anonfun$applyOrElse$15$$anonfun$apply$15.apply(routes_routing.scala:258) ~[na:na]
at play.core.Router$HandlerInvoker$$anon$6$$anon$2.invocation(Router.scala:164) ~[play_2.10.jar:2.1.1]
at play.core.Router$Routes$$anon$1.invocation(Router.scala:345) ~[play_2.10.jar:2.1.1]
at play.core.j.JavaAction$$anon$1.call(JavaAction.scala:31) ~[play_2.10.jar:2.1.1]
at play.GlobalSettings$1.call(GlobalSettings.java:63) ~[play_2.10.jar:2.1.1]
at play.mvc.Security$AuthenticatedAction.call(Security.java:39) ~[play_2.10.jar:2.1.1]
at play.core.j.JavaAction$$anon$2.apply(JavaAction.scala:74) ~[play_2.10.jar:2.1.1]
at play.core.j.JavaAction$$anon$2.apply(JavaAction.scala:73) ~[play_2.10.jar:2.1.1]
at play.libs.F$Promise$PromiseActor.onReceive(F.java:420) ~[play_2.10.jar:2.1.1]
at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:159) ~[akka-actor_2.10.jar:na]
at akka.actor.ActorCell.receiveMessage(ActorCell.scala:425) ~[akka-actor_2.10.jar:na]
at akka.actor.ActorCell.invoke(ActorCell.scala:386) ~[akka-actor_2.10.jar:na]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:230) ~[akka-actor_2.10.jar:na]
at akka.dispatch.Mailbox.run(Mailbox.scala:212) ~[akka-actor_2.10.jar:na]
at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(AbstractDispatcher.scala:502) ~[akka-actor_2.10.jar:na]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:262) ~[scala-library.jar:na]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:975) ~[scala-library.jar:na]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1478) ~[scala-library.jar:na]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104) ~[scala-library.jar:na]
cv似乎返回空。 –
你說的是正確的，問題是因爲它在這種情況下應該返回false否則返回false。 – Savins
發佈異常的完整堆棧跟蹤。 –