Null pointer Exception in Spring Boot Data Jpa

Question

Controller

@RequestMapping(value=ApiName.BLOG_LIST_FEW, method=RequestMethod.POST,produces=ApiName.CHARSET)
        public ResponseEntity<ApiResponse> blogListFew(@RequestBody String user){
            try {
                UserReqModel userReq=JsonUtill.convertJsonToJava(user,UserReqModel.class);
                Map<String,Object> resp=userService.blogListFew(userReq.getPageNo());
                if( !resp.containsKey("error")) {
                    return responseUtil.successResponse(resp);
                }
                else {
                    return responseUtil.failRsponse(resp.get("error"));
                }
                
            }
            catch(Exception ex) {
                
                return responseUtil.badResponse(ex);
            }
        }

Service

public Map<String, Object> blogListFew(Integer pageNo) {
        Map<String, Object> resp = new HashMap<>();
        List<Map<String, String>> arlMap = new ArrayList<>();
        try {

            int pageSize = 4;

            System.out.println("here in the service 1");

            System.out.println("here in the service 2");
            Page<Blog> blogList = blogRepo.findByIsActiveOrderByCreateDateDesc(YesNO.YES,
                    PageRequest.of(pageNo, pageSize));
            System.out.println("blogListb-->"+blogList);
            
            if (blogList == null) {
                resp.put("error", "not found");
                return resp;
            }
                blogList.forEach(blog -> {
                    HashMap<String, String> hashMap = new HashMap<String, String>();
                    hashMap.put("description",
                            (blog.getDescription() != null) ? blog.getDescription().substring(0, 1) + "..." : "");
                    hashMap.put("blogTitle", (blog.getBlogTitle() != null) ? blog.getDescription() : "");
                    hashMap.put("verticalImageUrl", (blog.getImageVertUrl() != null) ? blog.getImageVertUrl() : "");
                    hashMap.put("blogId", blog.getBlogId().toString());
                    hashMap.put("isTrendingPriority", Integer.toString(blog.getTrendingPriority()));
                    arlMap.add(hashMap);
                });
                resp.put("totalPage", blogList.getTotalPages());
                resp.put("blogList", arlMap);

            
    
            
            return resp;

        } catch (Exception ex) {
            System.out.println(ex);
            System.out.println(ex.getMessage());
            resp.put("error","sxception occured");
            
            return resp;
        }

    }

output in console-->

here in the service 1
here in the service 2
java.lang.NullPointerException
null

I was checking for the condition when there is no record for blog table and that time I called my api but that time i know it should return null for that I have check and i will return some respones but I dont know how I am getting null pointer exception in that because no way any operation performed when it will be null even tried to print blogList but even that statement not executed that means it is giving error in jpa query method and it is working fine when there are records in it.

I dont know how it is getting null pointer Exception for that very reason i put the check on bloglist. Please anyone help me with this

Shailesh Chandra · Accepted Answer · 2020-10-14 11:57:29Z

1

you need to check couple of things

You need to check if BlogRepo is @Autowired
you can also print BlogRepo in your System.out so that you get sure if it is null or not
You need to check if you have @EnableJpaRepositories

@EnableJpaRepositories(basePackages = "com.persistence.dao")

answered Oct 14, 2020 at 11:57

Shailesh Chandra

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2 Comments

Rajat Agrawal Over a year ago

it is autowired and I already and on printing it is giving class name like org.springframework.data.jpa.repository.support.SimpleJpaRepository@147990de and it is in base package can you tell more the reason why I am not able to understand is it is working when there are records present

Shailesh Chandra Over a year ago

can you use ex.printStackTrace(); instead of System.out.println(ex); so that we can pin point exact line of NPE, also please pring pageNo

allkenang · Accepted Answer · 2020-10-14 10:19:23Z

1

Did you inject your blogRepo into the controller?

@Autowire

{BlogRepo_class_name} blogRepo

where "BlogRepo_class_name" is the name of your blogRepo class.

answered Oct 14, 2020 at 10:19

allkenang

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2 Comments

Rajat Agrawal Over a year ago

its already added in my code @Autowired private BlogRepo blogRepo;

Rajat Agrawal Over a year ago

yes i injected into the controller and the proof is it works when there are records present in it

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