Spring IoC - Dependency Injection -> NullPointerException
I have this structure:
An interface IProjectService and this is implemented by ProjectServiceImpl.
Now I have a controller in which I want to use the 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;
}
}
In my applicationContext.xml I have these lines of code:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<bean id="projectServiceImpl" class="com.mydomain.project.service.impl.ProjectServiceImpl" />
<bean id="projectService" class="com.mydomain.project.service.IProjectService">
<property name="projectServiceImpl">
<ref local="projectServiceImpl"/>
</property>
</bean>
</beans>
But if I run my application I get an error (NullPointerException) in my MyDIController in this line of code:
... = this.projectServiceImpl.getProject(12);
The problem is, that
this.projectServiceImpl
is null and so it seems that the Dependency Injection does not work.
What's wrong here, does anyone know?
Best Regards Tim.
Update:
Full Error Trace:
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.ApplicationFilterCha开发者_如何学Cin.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:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<bean id="projectService" class="com.mydomain.project.service.impl.ProjectServiceImpl" />
<bean id="myDIController" class="com.mydomain.project.controller.MyDIController">
<property name="projectServiceImpl">
<ref local="projectService"/>
</property>
</bean>
</beans>
web.xml:
<servlet>
<servlet-name>project</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/app-config.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
app-config.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<!-- Scans the classpath of this application for @Components to deploy as beans -->
<context:component-scan base-package="com.mydomain.project" />
<!-- Application Message Bundle -->
<bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
<property name="basename" value="/WEB-INF/messages/messages" />
<property name="cacheSeconds" value="0" />
</bean>
<!-- Configures Spring MVC -->
<import resource="mvc-config.xml" />
</beans>
You haven;t injected property projectServiceImpl for MyDIController
Conf. should be like
<bean id="projectService" class="com.mydomain.project.service.impl.ProjectServiceImpl" />
<bean id="myDIController " class="com.mydomain.project.service.MyDIController">
<property name="projectServiceImpl">
<ref local="projectService"/>
</property>
</bean>
in web.xml
<web-app>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/application-context.xml
</param-value>
</context-param>
.
.
.
.
<servlet>
.
.
.
You have a few options.
- Declare an XML Bean for your controller and set the property for your service in that.
- Depending on your version of Spring, use Spring's Annotation/Autowiring support.
If you choose number 2, be sure to include <context:component-scan base-package="com.your.package"/> in your xml configuration and mark your controller class with @Controller and @Autowired for your projectService property.
加载中,请稍侯......
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