Spring IoC – dependency injection – > NullPointerException
我有这个结构：
接口IProjectService，由ProjectServiceImpl实现。
现在我有一个控制器，我想在其中使用dependency injection：
@Controller @RequestMapping(value="/testFolder") public class MyDIController { ... private IProjectService projectServiceImpl; public void setProjectServiceImpl(IProjectService projectServiceImpl) { this.projectServiceImpl= projectServiceImpl; } ... @RequestMapping(value="/project", method=RequestMethod.GET) public @ResponseBody Project getProject() { Project project = this.projectServiceImpl.getProject(12); // line 37! (id 12 is a test case, it does exist, here is he error: this.projectServiceImpl = null) return project; } } 在我的applicationContext.xml中，我有以下几行代码：
但是，如果我运行我的应用程序，我在我的MyDIController中的代码行中出现错误（NullPointerException）：
... = this.projectServiceImpl.getProject(12);
问题是，那
this.projectServiceImpl
为null，因此似乎dependency injection不起作用。
这有什么不对，有谁知道？
最诚挚的问候蒂姆。
更新：
完整错误跟踪：
09.12.2010 11:16:53 org.apache.catalina.core.ApplicationDispatcher invoke SCHWERWIEGEND: Servlet.service() for servlet project threw exception java.lang.NullPointerException at com.mydomain.project.controller.MyDIController.getAllProjects(MyDIController.java:37) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302) at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:195) at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:159) at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141) at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619) 09.12.2010 11:16:53 org.apache.catalina.core.StandardWrapperValve invoke SCHWERWIEGEND: Servlet.service() for servlet default threw exception java.lang.NullPointerException at com.mydomain.project.controller.MyDIController.getProject(MyDIController.java:37) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549) at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:646) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302) at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:195) at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:159) at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141) at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90) at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Thread.java:619)
`
applicationContext.xml中：
web.xml中：
project org.springframework.web.servlet.DispatcherServlet contextConfigLocation /WEB-INF/spring/app-config.xml 1
APP-config.xml文件：
你projectServiceImpl为MyDIController注入属性MyDIController
CONF。 应该是这样的
在web.xml中
contextConfigLocation /WEB-INF/application-context.xml . . . . . . .
你有几个选择。
- 为您的控制器声明一个XML Bean，并为其设置服务的属性。
- 根据您的Spring版本，使用Spring的Annotation / Autowiring支持。
如果选择数字2，请确保在xml配置中包含