NullPointerException in sprinboot+jpa+gradle

Question

As the title says I'm getting a null pointer exception when I call a method in my data repository to retrieve some data. I'm making an API with the Spring Boot framework using JPA+Hibernate

I've checked if the method parameters are null or empty but all the parameters are good. I also tried changing the query but I'm getting the same nullpointerexception on execution time.


java.lang.NullPointerException: Cannot invoke "com.cg.entites.User.getUsername()" because "u2" is null
    at com.cg.contoller.UserController.addUser(UserController.java:45) ~[main/: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-5.3.6.jar:5.3.6]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:652) ~[tomcat-embed-core-9.0.45.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.6.jar:5.3.6]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.45.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.6.jar:5.3.6]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.6.jar:5.3.6]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.45.jar:9.0.45]
    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-9.0.45.jar:9.0.45]
    at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]

1.User class

package com.cg.entites;

import java.io.Serializable;

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

@Entity
@Table(name="Users")
public class User implements Serializable{
    
    private static final long serialVersionUID = 1L;
    @Id
    private int id;
    private String username;
    private String password;
    private String role;
    
    
    public User() {
        super();
    }


    public User(int id, String username, String password, String role) {
        super();
        this.id = id;
        this.username = username;
        this.password = password;
        this.role = role;
    }


    public int getId() {
        return id;
    }


    public void setId(int id) {
        this.id = id;
    }


    public String getUsername() {
        return username;
    }


    public void setUsername(String username) {
        this.username = username;
    }


    public String getPassword() {
        return password;
    }


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


    public String getRole() {
        return role;
    }


    public void setRole(String role) {
        this.role = role;
    }


    @Override
    public String toString() {
        return "User [id=" + id + ", username=" + username + ", password=" + password + ", role=" + role + "]";
    }
    
    
}

2.UserRepository

package com.cg.dao;




import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;

import com.cg.entites.User;
import com.cg.exceptions.InvalidException;



@Repository("urepo")
public interface UserRepository extends JpaRepository<User,Integer>{
    @Query("SELECT u FROM User u WHERE u.username = :username")
    public User getUserByUsername(@Param("username") String username);
}

3.UserService

package com.cg.service;

import java.util.List;
import java.util.Optional;

import javax.transaction.Transactional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;
import org.springframework.stereotype.Service;


import com.cg.dao.UserRepository;
import com.cg.entites.User;
import com.cg.exceptions.InvalidException;

@Service
public class UserServiceImpl implements UserService{

    @Autowired
    UserRepository urepo;
    @Override
    public List<User> getAllUsers() {
        // TODO Auto-generated method stub
        List<User> ulist=urepo.findAll();
        return ulist;
        
    }
    @Override
    @Transactional
    public User addUser(User user) {
        // TODO Auto-generated method stub
        return urepo.save(user);
    }
    @Override
    @Transactional
    public User removeUser(int userId) {
        // TODO Auto-generated method stub
        Optional<User> u=urepo.findById(userId);
        if(u.empty()!=null) {
            urepo.deleteById(userId);
            return u.get();
        }
    return null;
    }
    @Override
    @Transactional
    public User validateUser(String username, String password) throws InvalidException{
        User u=urepo.getUserByUsername(username);
        System.out.println("u details"+u);
        if(u==null) {
            System.out.println("InValid User");
            }
        return u;
        
    }

    

}

4.userException

package com.cg.exceptions;

public class InvalidException  extends Exception {
    public InvalidException(String msg) {
        super(msg);
    }
    
}

5.UserContoller

package com.cg.contoller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PatchMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.cg.dao.UserRepository;
import com.cg.entites.User;
import com.cg.exceptions.InvalidException;
import com.cg.service.UserService;


@RestController
@RequestMapping("/api/v1")
public class UserController {
    @Autowired
    UserService service;
    @Autowired
    UserRepository urepo;
 
@GetMapping("/user")
    public List<User> findUser(){
        return urepo.findAll();
        
    }
 @PostMapping("/user")
    public ResponseEntity<User> addUser(@RequestBody User user) throws InvalidException{
        User u2=service.validateUser(user.getUsername(),user.getPassword());
        System.out.println("Valid u2 "+u2);
        
        if(u2.getUsername()==null && u2.getPassword()==null) {
            User user1 = service.addUser(u2);
            System.out.println("user successfully registered");
        }
        else {
        System.out.println("add user method accessed");
         throw new InvalidException("Invalid user in controller");
    }
        return null;
 }
 @DeleteMapping("/user/{id}")
    public ResponseEntity<User> deleteUser(@PathVariable int id) {
        
        User user1 = service.removeUser(id);
        
        if(user1!=null) {
            System.out.println("User successfully removed");
            return new ResponseEntity<>(user1,HttpStatus.OK);
        }
        
        System.out.println("delete user method accessed");
        //throw new UserNotFoundException("Invalid user id");
        return null;
    }
 

}

6.build.grdale

plugins {
    id 'org.springframework.boot' version '2.4.5'
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'java'
}

group = 'com.cg'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    runtimeOnly 'com.oracle.database.jdbc:ojdbc8'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    
}

test {
    useJUnitPlatform()
}

I don't know where the error is can someone help me.

Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — dan1st, May 09 '21 at 16:31
I am not sure but seems like problem is with variable urepo. In your repository, replace @Repository("urepo") with @Repository and try again — Sridhar Patnaik, May 09 '21 at 16:32

score 0 · Answer 1 · answered May 09 '21 at 20:00

As I can see from the stack trace, the problem is in the line before the last one of this piece of code

        User u2=service.validateUser(user.getUsername(),user.getPassword());
        System.out.println("Valid u2 "+u2);
        
        if(u2.getUsername()==null && u2.getPassword()==null) {
             User user1 = service.addUser(u2);

u2 is null. This code is called from controller method addUser, so user probably doesn't exist. u2 comes from validateUser method and it simply calls you repository method. Since user doesn't exist, the repository should return null.

As a conclude from your code, you thought, that repository should return a non null User object with all fields equal to null. Because that's when you decide to add user.

Please tell me if I was correct ))

It's really weird, that you add User with name == null and password == null by the way ))

NullPointerException in sprinboot+jpa+gradle

1 Answers1