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[英]Error java.lang.NullPointerException while calling class method
[英]java.lang.NullPointerException while calling from controller
我的Spring Boot程序正在編譯而沒有任何問題,但每當我點擊注冊鏈接時,它都會拋出NullPointerException錯誤。 我真的不知道可能導致這種情況的原因。 鑒於以下是錯誤: -
java.lang.NullPointerException: null
at com.concretepage.controller.UserInfoController.registration(UserInfoController.java:32) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.8.0_171]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.8.0_171]
UserinfoController類如下: -
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
import com.concretepage.entity.ProjectLevel;
import com.concretepage.service.LevelService;
import com.concretepage.service.UserInfoService;
@Controller
@RequestMapping("app")
public class UserInfoController {
@Autowired
private UserInfoService userInfoService;
private LevelService levelService;
@GetMapping("login")
public ModelAndView login() {
ModelAndView mav = new ModelAndView();
mav.setViewName("custom-login");
return mav;
}
@GetMapping("registration")
public ModelAndView registration() {
ModelAndView mav = new ModelAndView();
List<ProjectLevel> levels = levelService.getAllLevels();
mav.addObject("Levels", levels);
mav.setViewName("registration");
return mav;
}
@GetMapping("secure/project-details")
public ModelAndView getAllUserProjects() {
ModelAndView mav = new ModelAndView();
mav.addObject("userProjects", userInfoService.getAllUserProjects());
mav.setViewName("projects");
return mav;
}
錯誤在線 -
List<ProjectLevel> levels = levelService.getAllLevels();
LevelServiceImpl類如下: -
package com.concretepage.service;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.concretepage.entity.ProjectLevel;
import com.concretepage.repositories.LevelRepository;
@Service
public class LevelServiceImpl implements LevelService {
@Autowired
private LevelRepository levelRepository;
@Override
public List<ProjectLevel> getAllLevels() {
List<ProjectLevel> levelList = levelRepository.findAll();
return levelList;
}
}
只需更改這段代碼:
@Autowired
private UserInfoService userInfoService;
private LevelService levelService;
至
@Autowired
private UserInfoService userInfoService;
@Autowired
private LevelService levelService;
您必須為私有LevelService levelService使用單獨的@Autowired;
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