使用PlayFramework 2.4.2的ProvisionException [英] ProvisionException using PlayFramework 2.4.2
问题描述
我正在将一个项目从Play 2.2.4迁移到2.4.2,但遇到了一个我无法理解和解决的异常.
I am migrating a project from Play 2.2.4 to 2.4.2 and I am getting an exception which I am not able to understand and solve.
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
发生这种情况是因为我为WS API添加了依赖项注入,例如:
It occurs since I added the dependency injection for the WS API like:
public class Application extends Controller {
@Inject
WSClient ws;
WSRequest request = ws.url("https://...");
...
}
build.sbt
文件包含必要的配置
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
可能遗漏或做错了什么?
What could be missing or be done wrong?
推荐答案
此行导致Nullpointer:
当Guice实例化Application
类时,ws.url("https://...");
ws为null.此外,将request
作为控制器字段不是线程安全的.将您的代码更改为以下内容:
This line causes Nullpointer:
ws.url("https://...");
ws is null by the time when Guice instantiates Application
class. More over, having a request
as controller field is not thread safe. Change your code to following:
public class Application extends Controller {
private WSClient ws;
@Inject
public Application(WSClient ws) {
this.ws = ws;
WSRequest request = this.ws.url("https://...");
...
}
}
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