在Spring Boot应用程序中面临java.lang.NullPointerException

问题描述 投票：0回答：2

我正在尝试使用 Spring Boot 制作登录页面。我有三类用户：学生、学院、公司。当我检查用户是否存在时，以下代码对学生工作正常，但对其他两个人不起作用。它为 servlet [dispatcherServlet] 在路径 [] 的上下文中提供了 NullPointerException 和消息 Servlet.service() 抛出异常 [请求处理失败；嵌套异常是 java.lang.NullPointerException: 无法调用“com.springboot.controller.repository.CollegeRepo.findByEmail(String)”，因为“this.clgrepo”为 null] 其根本原因 我在数据库中为三个类别有三个不同的表。如果我做错了什么，请告诉我。 以下是我的代码：

主课


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;


@EntityScan(basePackages="com.springboot.controller.model")
@EnableJpaRepositories(basePackages="com.springboot.controller.repository")
@SpringBootApplication
public class CunsultustodayWebServicesApplication {

    public static void main(String[] args) {
        SpringApplication.run(CunsultustodayWebServicesApplication.class, args);
    }

}

LoginController.java


import org.springframework.beans.factory.annotation.Autowired;


import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.ModelAndView;

import com.springboot.controller.model.CollegeReg;
import com.springboot.controller.model.CompanyReg;
import com.springboot.controller.model.User;
import com.springboot.controller.repository.CollegeRepo;
import com.springboot.controller.repository.CompanyRepo;
import com.springboot.controller.repository.UserRepo;
import com.springboot.controller.services.StudentService;

@RestController
public class LoginController {

    @Autowired(required=true)
    private StudentRepo stdrepo;    
    private CollegeRepo clgrepo;
    private CompanyRepo cmprepo;
    
    @RequestMapping("/")
    public ModelAndView checkMVC()
    {
        ModelAndView mav= new ModelAndView("Login");
                
        return mav;
    }
    
    @RequestMapping("/login")
    public ModelAndView loginHome(@RequestParam(value="email" ,required=true) String email, @RequestParam(value="password", required=true) String password, Model model)
    {
        StudentReg u= null;
            
        u= stdrepo.findByEmail(email);
        if(u!=null) {
          model.addAttribute("email", email);
          ModelAndView mav=new ModelAndView("HomePage");
          return mav;
        }
        else {
            CollegeReg c=null;
            c=clgrepo.findByEmail(email);
            if(c!=null) {
                model.addAttribute("email", email);
                  ModelAndView mav=new ModelAndView("HomePage");
                  return mav;
            }
            else {
                CompanyReg co=null;
                co=cmprepo.findByEmail(email);
                if(co!=null) {
                    model.addAttribute("email", email);
                      ModelAndView mav=new ModelAndView("HomePage");
                      return mav;
                }
            }
        }
        
        //model.addAttribute("error", "User not found");
        ModelAndView mav=new ModelAndView("Login");
        return mav;
    
    }}

StudentRepo.java


import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Service;

import com.springboot.controller.model.StudentReg;


@Service("StudentRepo")
public interface StudentRepo extends JpaRepository<StudentReg,Integer> {

     StudentReg findByEmail(String email);

}

CollegeRepo.java


import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Service;

import com.springboot.controller.model.CollegeReg;

@Service("CollegeRepo")
public interface CollegeRepo extends JpaRepository<CollegeReg,Integer>{

    CollegeReg findByEmail(String email);
}

CompanyRepo.java


import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Service;

import com.springboot.controller.model.CompanyReg;

@Service("CompanyRepo")
public interface CompanyRepo extends JpaRepository<CompanyReg,Integer> {

    CompanyReg findByEmail(String email);
}

StudentReg.java


import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Table;
import javax.persistence.Id;

@Entity
@Table(name="tbl_student_reg")
public class User {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="std_id")
    private int stdId;
    
    @Column(name="email")
    private String email;
    
    @Column(name="password")
    private String password;
    
    public User() {}


    public int getStdId() {
        return stdId;
    }

    public void setStdId(int stdId) {
        this.stdId = stdId;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    }

CollegeReg.java


import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="tbl_colleges_reg")
public class CollegeReg {

    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="clg_id")
    private int clgId;
    
    @Column(name="email")
    private String email;
        
    @Column(name="password")
    private String password;
    
    public CollegeReg() {
        super();
    }
    
    public int getClgId() {
        return clgId;
    }
    public void setClgId(int clgId) {
        this.clgId = clgId;
    }
        public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    }

CompanyReg.java

package com.springboot.controller.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="tbl_companies_reg")
public class CompanyReg {


    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="comp_id")
    private int compId;
    
    @Column(name="name")
    private String name;
    
    @Column(name="email")
    private String email;
    
    @Column(name="password")
    private String password;
    
    public CompanyReg() {
        super();
    }
    
    public int getCompId() {
        return compId;
    }
    public void setCompId(int compId) {
        this.compId = compId;
    }
    
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    
}

错误日志


java.lang.NullPointerException: Cannot invoke "com.springboot.controller.repository.CollegeRepo.findByEmail(String)" because "this.clgrepo" is null
    at com.springboot.controller.resource.LoginController.loginHome(LoginController.java:52) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) ~[tomcat-embed-core-9.0.43.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.4.jar:5.3.4]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.43.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.4.jar:5.3.4]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.4.jar:5.3.4]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.4.jar:5.3.4]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.4.jar:5.3.4]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:346) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:887) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1684) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.43.jar:9.0.43]
    at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]

请帮忙 谢谢！

java spring-boot hibernate spring-mvc jpa
2个回答
3
投票

存储库未注入。 在 

LoginController
中，可以使用存储库创建构造函数（首选方式）或将字段标记为 
@Autowired
。

3
投票

检查您的

LoginController
课程。

您仅在 

@Autowired
中有 
StudentRepo
，但其他 2 个存储库没有此类注释。它们不会被自动装配，并且默认设置为空。

也将 

@Autowired
注释也放置在那里，然后再次检查。

最新问题
© www.soinside.com 2019 - 2024. All rights reserved.