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从 Grails 开始,我已经安装了 Grails 版本 2.4.0,并在 GNU/Linux 上使用 JDK 1.7.0_55,我执行了以下一系列操作,但不断收到 NullPointerException。有人可以指出我遗漏或做错了什么吗?
grails create-app firstgrails
cd firstgrails
grails
grails> run-app
我转到 localhost:8080/firstgrails 并查看生成的页面。
接下来我会
grails> create-domain-class tag
然后转到firstgrails/grails-app/domain/firstgrails 文件夹并编辑Tag.groovy,使其包含:
// Tag.groovy
package firstgrails
class Tag {
String name
String description
}
下一步
grails> create-controller tag
并将firstgrails/grailsapp/controllers/firstgrails/TagController.groovy 编辑为
// TagController.groovy
package firstgrails
class TagController {
static scaffold = Tag
}
我在浏览器中重新加载,并且firstgrails.TagController被添加到可用列表中欢迎消息下的 Controller 。选择它,我创建一个包含名称和描述的标签,并且该标签按预期显示在标签列表中。但现在每当我尝试添加第二个标签时,我都会收到 500 错误:Internal Server Error with
URI: /firstgrails/tag/create
Class: java.lang.NullPointerException
Message: null
控制台中的跟踪是:
Error 2014-06-03 18:28:31,714 [http-bio-8080-exec-2] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [GET] /firstgrails/tag/create
Stacktrace follows:
Message: Error processing GroovyPageView: Error executing tag <g:form>: Error executing tag <g:render>: null
Line | Method
->> 527 | doFilter in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by GrailsTagException: Error executing tag <g:form>: Error executing tag <g:render>: null
->> 35 | doCall in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by GrailsTagException: Error executing tag <g:render>: null
->> 30 | doCall in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by NullPointerException: null
->> 333 | hash in java.util.concurrent.ConcurrentHashMap
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 988 | get in ''
| 141 | getValue in grails.util.CacheEntry
| 81 | getValue in ''
| 73 | doCall . in tag_create$_run_closure2_closure24
| 78 | doCall in tag_create$_run_closure2
| 81 | run . . . in tag_create
| 189 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter
| 63 | doFilter in grails.plugin.cache.web.filter.AbstractFilter
| 1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
| 615 | run . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run in java.lang.Thread
| Error 2014-06-03 18:30:33,050 [http-bio-8080-exec-9] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [GET] /firstgrails/tag/create
Stacktrace follows:
Message: Error processing GroovyPageView: Error executing tag <g:form>: Error executing tag <g:render>: null
Line | Method
->> 527 | doFilter in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by GrailsTagException: Error executing tag <g:form>: Error executing tag <g:render>: null
->> 35 | doCall in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by GrailsTagException: Error executing tag <g:render>: null
->> 30 | doCall in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by NullPointerException: null
->> 333 | hash in java.util.concurrent.ConcurrentHashMap
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 988 | get in ''
| 141 | getValue in grails.util.CacheEntry
| 81 | getValue in ''
| 73 | doCall . in tag_create$_run_closure2_closure24
| 78 | doCall in tag_create$_run_closure2
| 81 | run . . . in tag_create
| 189 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter
| 63 | doFilter in grails.plugin.cache.web.filter.AbstractFilter
| 1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
| 615 | run . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run in java.lang.Thread
| Error 2014-06-03 18:32:21,796 [http-bio-8080-exec-5] ERROR errors.GrailsExceptionResolver - NullPointerException occurred when processing request: [GET] /firstgrails/tag/create
Stacktrace follows:
Message: Error processing GroovyPageView: Error executing tag <g:form>: Error executing tag <g:render>: null
Line | Method
->> 527 | doFilter in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by GrailsTagException: Error executing tag <g:form>: Error executing tag <g:render>: null
->> 35 | doCall in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by GrailsTagException: Error executing tag <g:render>: null
->> 30 | doCall in /tag/create
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Caused by NullPointerException: null
->> 333 | hash in java.util.concurrent.ConcurrentHashMap
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| 988 | get in ''
| 141 | getValue in grails.util.CacheEntry
| 81 | getValue in ''
| 73 | doCall . in tag_create$_run_closure2_closure24
| 78 | doCall in tag_create$_run_closure2
| 81 | run . . . in tag_create
| 189 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter
| 63 | doFilter in grails.plugin.cache.web.filter.AbstractFilter
| 1145 | runWorker in java.util.concurrent.ThreadPoolExecutor
| 615 | run . . . in java.util.concurrent.ThreadPoolExecutor$Worker
^ 745 | run in java.lang.Thread
最佳答案
我尝试过并能够重现它。如果我们生成 View ,那么它就可以解决,但如果没有 View ,则会出现错误。 grails
jira
中存在问题,请参阅 this issue他们已经为其提供了补丁。
希望这有帮助。
关于grails - 搭建第一个 Grails 应用程序时出现 NullPointer 异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24020887/
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