我已经成功地将现有的 Java 项目用于我的 Scala 项目,但是在使用 Java 单例时遇到了 NoClassDefFoundError:
public class SpecificUser extends BasicUser {
private static SpecificUser INSTANCE = new SpecificUser();
protected SpecificUser() { }
public static SpecificUser getInstance() {
return INSTANCE;
}
...
}
这是确切的错误:
play.api.Application$$anon$1: Execution exception[[RuntimeException: java.lang.NoClassDefFoundError: Could not initialize class SpecificUser]]
at play.api.Application$class.handleError(Application.scala:296) ~[play_2.11-2.3.5.jar:2.3.5]
at play.api.DefaultApplication.handleError(Application.scala:402) [play_2.11-2.3.5.jar:2.3.5]
at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$14$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:205) [play_2.11-2.3.5.jar:2.3.5]
at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$14$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:202) [play_2.11-2.3.5.jar:2.3.5]
at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:36) [scala-library-2.11.1.jar:na]
Caused by: java.lang.RuntimeException: java.lang.NoClassDefFoundError: Could not initialize class SpecificUser
at play.api.mvc.ActionBuilder$$anon$1.apply(Action.scala:523) ~[play_2.11-2.3.5.jar:2.3.5]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:130) ~[play_2.11-2.3.5.jar:2.3.5]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:130) ~[play_2.11-2.3.5.jar:2.3.5]
at play.utils.Threads$.withContextClassLoader(Threads.scala:21) ~[play_2.11-2.3.5.jar:2.3.5]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:129) ~[play_2.11-2.3.5.jar:2.3.5]
Caused by: java.lang.NoClassDefFoundError: Could not initialize class SpecificUser
at controllers.UsersController$$anonfun$usersDatatable$1.apply(UsersController.scala:36) ~[classes/:na]
at controllers.UsersController$$anonfun$usersDatatable$1.apply(UsersController.scala:34) ~[classes/:na]
at controllers.security.Authentication$$anonfun$AuthenticatedAction$1.apply(AuthenticatedController.scala:21) ~[classes/:na]
at controllers.security.Authentication$$anonfun$AuthenticatedAction$1.apply(AuthenticatedController.scala:19) ~[classes/:na]
at play.api.mvc.ActionBuilder$$anonfun$apply$16.apply(Action.scala:433) ~[play_2.11-2.3.5.jar:2.3.5]
这些问题可能有助于确定在 Scala 中访问静态方法可能无法访问,但无助于确定可行的解决方案:
https://stackoverflow.com/a/4448069/1359765
https://stackoverflow.com/a/21303729/1359765
如何在 Scala 中使用我的单例对象?
更新
我在我正在使用的 java 依赖项目中创建了一个单例,它运行良好。问题是当单例继承自 BasicUser 时,它位于我正在使用的另一个 java 依赖项项目中。