【求助】空指针异常

Question

代码：
public class QueryApplyController  extends AbstractController {
private UserService userService;
protected ModelAndView handleRequestInternal(HttpServletRequest
req, HttpServletResponse rsp) throws Exception {
Map<String, String> criteria = new HashMap<String, String>();
ArrayList<UserApplyPojo> list = new ArrayList<UserApplyPojo>();
String applyType = req.getParameter("SelectApplyType");
String applyDateStart = req.getParameter("applyDateStart");
String applyDateEnd = req.getParameter("applyDateEnd");
if(!applyType.equals("4")){
criteria.put(KeyNames.TYPE, applyType);
criteria.put(KeyNames.APPLY_DATE_START, applyDateStart);
criteria.put(KeyNames.APPLY_DATE_END, applyDateEnd);
list = this.getUserService().queryApply(criteria); //在这里报空指针异常
                }else{
//全部类型
criteria.put(KeyNames.APPLY_DATE_START, applyDateStart);
criteria.put(KeyNames.APPLY_DATE_END, applyDateEnd);
list = this.getUserService().queryApply1(criteria);//这里也会报空指针 }
Map model = new HashMap();
model.put("queryApply", list);

return new ModelAndView("applyPage", model);
}
public UserService getUserService() {
return userService;
} public void setUserService(UserService userService) {
this.userService = userService;
}}异常：
java.lang.NullPointerException
at com.isl.pms.controller.common.QueryApplyController.handleRequestInternal(QueryApplyController.java:38)
at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:875)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:511)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
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 com.isl.pms.controller.filter.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:27)
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:103)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)
我还试了试，在这个类里边写其他的只要是调用数据库的都会报空指针异常。我的其他功能的controller类也都这么写的，其他的也没报错啊，我是新手小白，希望大家能帮我看看。（顺便想说，我有个两个其他的类明明是调用的同一个函数，传的参数也一样，但一个报空指针，一个运行正常，都把我弄懵了）java 空指针异常java空指针异常

Answer 1

请问userService没注入是什么意思？

Answer 2

userServicem没设置值。。所以是空指针。

Answer 3

userService 初始化一个值 null

Answer 4

 this.getUserService()返回一个null，再执行queryApply（XX）当然是nullpointerexception

Answer 5

userService这个对象要注入，不知道你们是通过配置xml，还是注解，注解的话就如下
@Autowired
private UserService userService;

Answer 6

@Resource
private UserService userService;
如果有用到注解的话