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我正在使用Grails 2.0.0。幾天前我開始使用Webflow插件，但今天遇到了一些麻煩。當我運行應用程序並擊中使用webflow的控制器時，我得到一個NullPointerException。如果我重新加載，我也會得到同樣的結果。如果我向控制器源文件添加一個空格（或者任何更改，只需強制重新編譯）並使用run-app保存，Grails會重新編譯控制器，並且後續請求可以正常工作。不幸的是，我不知道錯誤何時第一次出現。我一直無法將錯誤追溯到我做出的特定更改。Grails NPE對控制器的所有請求，直到重新編譯而不更改爲代碼
我該如何深入挖掘？爲什麼在運行時重新編譯控制器會修復NPE？
這裏的控制器代碼，我可以用它來重現問題：
class ServicesController {
def index() {
redirect(action: "request")
}
def requestFlow = {
selectAssessments {
on("next") {
}.to("productInfo")
on("cancel").to("finish")
}
}
}
而這裏的控制檯日誌：
| Error 2012-03-18 21:43:11,272 ["http-bio-8080"-exec-4] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [GET] /project/services/request
Stacktrace follows:
Message: null
Line | Method
->> 886 | runTask in java.util.concurrent.ThreadPoolExecutor$Worker
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 908 | run in ''
^ 680 | run . . in java.lang.Thread
| Error 2012-03-18 21:43:13,261 ["http-bio-8080"-exec-4] ERROR servlet.GrailsDispatcherServlet - HandlerInterceptor.afterCompletion threw exception
Message: No value for key [org.hibernate.impl.SessionFactoryI[email protected]] bound to thread ["http-bio-8080"-exec-4]
Line | Method
->> 886 | runTask in java.util.concurrent.ThreadPoolExecutor$Worker
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 908 | run in ''
^ 680 | run . . in java.lang.Thread
| Error 2012-03-18 21:43:14,199 ["http-bio-8080"-exec-5] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [GET] /project/services/request - parameters:
execution: e1s1
Stacktrace follows:
Message: null
Line | Method
->> 886 | runTask in java.util.concurrent.ThreadPoolExecutor$Worker
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 908 | run in ''
^ 680 | run . . in java.lang.Thread
| Error 2012-03-18 21:43:14,262 ["http-bio-8080"-exec-5] ERROR servlet.GrailsDispatcherServlet - HandlerInterceptor.afterCompletion threw exception
Message: No value for key [[email protected]] bound to thread ["http-bio-8080"-exec-5]
Line | Method
->> 886 | runTask in java.util.concurrent.ThreadPoolExecutor$Worker
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 908 | run in ''
^ 680 | run . . in java.lang.Thread
從目標/ stacktrace.log：
2012-03-23 22:00:33,470 ["http-bio-8080"-exec-3] ERROR StackTrace - Full Stack Trace:
java.lang.NullPointerException
at org.codehaus.groovy.grails.orm.hibernate.support.GrailsOpenSessionInViewInterceptor.postHandle(GrailsOpenSessionInViewInterceptor.java:75)
at org.springframework.web.servlet.handler.WebRequestHandlerInterceptorAdapter.postHandle(WebRequestHandlerInterceptorAdapter.java:61)
at org.codehaus.groovy.grails.web.servlet.GrailsDispatcherServlet.doDispatch(GrailsDispatcherServlet.java:342)
...
2012-03-23 22:00:33,490 ["http-bio-8080"-exec-3] ERROR StackTrace - Full Stack Trace:
java.lang.NullPointerException
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
...
2012-03-23 22:00:36,725 ["http-bio-8080"-exec-3] ERROR StackTrace - Full Stack Trace:
java.lang.IllegalStateException: No value for key [[email protected]] bound to thread ["http-bio-8080"-exec-3]
at org.springframework.transaction.support.TransactionSynchronizationManager.unbindResource(TransactionSynchronizationManager.java:209)
at org.springframework.orm.hibernate3.support.OpenSessionInViewInterceptor.afterCompletion(OpenSessionInViewInterceptor.java:211)