Java 使用PlayFramework 2.4.2的ProvisionException

我正在将一个项目从Play 2.2.4迁移到Play 2.4.2，我遇到了一个我无法理解和解决的异常

Unexpected exception

ProvisionException: Unable to provision, see the following errors:

1) Error injecting constructor, java.lang.NullPointerException
  at controllers.Application.<init>(Application.java:33)
  while locating controllers.Application
    for parameter 1 at router.Routes.<init>(Routes.scala:36)
  while locating router.Routes
  while locating play.api.inject.RoutesProvider
  while locating play.api.routing.Router

1 error

build.sbt

文件包括必要的配置

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

// Play provides two styles of routers, one expects its actions to be injected, the
// other, legacy style, accesses its actions statically.
routesGenerator := InjectedRoutesGenerator

---

哪些内容可能会丢失或出错？

此行会导致空指针：

ws.url（“https://...");应用程序

类时，code>ws为空。此外，将

请求

作为控制器字段不是线程安全的。将代码更改为以下内容：

public class Application extends Controller {

    private WSClient ws;

    @Inject
    public Application(WSClient ws) {

        this.ws = ws;
        WSRequest request = this.ws.url("https://...");

        ...
    }
}

---

谢谢你，这解决了我的问题！我想知道，如果播放文档不起作用，为什么会这样声明：

WSRequest-request=ws.url（“http://example.com");此行应属于控制器方法。
public class Application extends Controller {

    private WSClient ws;

    @Inject
    public Application(WSClient ws) {

        this.ws = ws;
        WSRequest request = this.ws.url("https://...");

        ...
    }
}