Getting NULL pointer exception while uploading object to database using JPA

Question

In my code i have read an excel sheet and passed the read parameter from excel sheet to method

@RestController
@RequestMapping("/api/v1")
public class ExcelController3 {

    private MultipartFile uploadfile;

    @Autowired
   private EmployeeRepository employeeRepository;


    @RequestMapping(value = "/upload3", method = RequestMethod.POST, consumes = javax.ws.rs.core.MediaType.MULTIPART_FORM_DATA)
    public void uploadFileHandler(@RequestParam("name") String name,
                                  @RequestParam("file") MultipartFile file) throws IOException {


        this.uploadfile=file;
        System.out.println("*****************************");

        System.out.println("file.getOriginalFilename() " + file.getOriginalFilename());
        System.out.println("file.getContentType()" + file.getContentType());
        System.out.println("file.getInputStream() " + file.getInputStream());
        System.out.println("file.toString() " + file.toString());
        System.out.println("file.getSize() " + file.getSize());
        System.out.println("name " + name);
        System.out.println("file.getBytes() " + file.getBytes());
        System.out.println("file.hashCode() " + file.hashCode());
        System.out.println("file.getClass() " + file.getClass());
        System.out.println("file.isEmpty() " + file.isEmpty());


        try {
            ExcelController ex=new ExcelController();
            File f1=ex.convert(file);
       //     FileInputStream file = new FileInputStream(new File("E://Imp/Details.xlsx"));
            XSSFWorkbook workbook = new XSSFWorkbook(f1);
            XSSFSheet sheet = workbook.getSheetAt(0);
            Iterator<Row> rowIterator = sheet.iterator();
            rowIterator.next();
            while(rowIterator.hasNext())
            {
                Row row = rowIterator.next();
                //For each row, iterate through each columns
                Iterator<Cell> cellIterator = row.cellIterator();

                while(cellIterator.hasNext())
                {
                    Cell cell = cellIterator.next();
                    //This will change all Cell Types to String
                    cell.setCellType(Cell.CELL_TYPE_STRING);
                    switch(cell.getCellType())
                    {
                        case Cell.CELL_TYPE_BOOLEAN:
                            System.out.println("boolean===>>>"+cell.getBooleanCellValue() + "\t");
                            break;
                        case Cell.CELL_TYPE_NUMERIC:

                            break;
                        case Cell.CELL_TYPE_STRING:

                            List list=new ArrayList();
                            list.add(cell.getStringCellValue());

                            break;
                    }


                }
                name=row.getCell(0).getStringCellValue();
                String empid = row.getCell(1).getStringCellValue();
               String add=row.getCell(2).getStringCellValue();
              String  mobile=row.getCell(3).getStringCellValue();
                System.out.println(name+empid+add+mobile);
                ExcelController3 ex1=new ExcelController3();
             //   ex1.InsertRowInDB(name,empid,add,mobile);

                System.out.println("");
                Employee em=new Employee();

                em.setName(name);
                em.setEmpid(empid);
                em.setAddress(add);
                em.setMobile(mobile);
                System.out.println(em);
                System.out.println(em.getAddress());
                System.out.println(em.getEmpid());
                System.out.println(em.getMobile());
                System.out.println(em.getName());
                ex1.InsertRowInDB(name,empid,add,mobile,em);

            }
            workbook.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InvalidFormatException e) {
            e.printStackTrace();
        }
    }
    public void InsertRowInDB(String name,String empid,String add,String mobile,Employee em) {

//        System.out.println("name "+name);
//        System.out.println("empid "+empid);
//        System.out.println("add "+add);
//        System.out.println("mobile "+mobile);
//        Employee em=new Employee();
//
//        em.setName(name);
//        em.setEmpid(empid);
//        em.setAddress(add);
//        em.setMobile(mobile);
//        System.out.println(em);
//        System.out.println(em.getAddress());
//        System.out.println(em.getEmpid());
//        System.out.println(em.getMobile());
//        System.out.println(em.getName());


     employeeRepository.save(em);

//employeeRepository.save(em);
//        Statement stmt=db.con.createStatement();
//        PreparedStatement ps=null;
//        String sql="Insert into Employee(Name,EmployeeId,Address,ContactInfo) values(?,?,?,?)";
//        ps=db.con.prepareStatement(sql);
//        ps.setString(1, name);
//        ps.setString(2, empid);
//        ps.setString(3, add);
//        ps.setString(4, mobile);
//        ps.executeUpdate();

        System.out.println("Values Inserted Successfully");
    }



    public File convert(MultipartFile file) throws IOException {
        File convFile = new File(file.getOriginalFilename());
        convFile.createNewFile();
        FileOutputStream fos = new FileOutputStream(convFile);
        fos.write(file.getBytes());
        fos.close();
        return convFile;
    }


    @GetMapping(value="/upload")
    public ResponseEntity<Collection<Employee>> getallemployees(){
        Collection<Employee> el =employeeRepository.findAll();
        return new ResponseEntity<Collection<Employee>>(el, HttpStatus.OK);
    }
}

But it gives me null pointer exception at employeeRepository.save(em); . unable to find out reason i have autowired employeeRepository also and created proper pojo class for jpa.

Answer 1

So after reading your code again, the issue is because you use some "new" on your controller. This: ExcelController3 ex1=new ExcelController3(); creates a brand new instance of ExcelController3 that is not managed (i.e. no @Autowired or any other spring magic) and so the repository of ex1 is null.

You probably want to replace:

ExcelController3 ex1=new ExcelController3();
ex1.InsertRowInDB(name,empid,add,mobile,em);

by

this.InsertRowInDB(name,empid,add,mobile,em);

Also note that you should not store some uploaded file (private MultipartFile uploadfile;) on the controller (because every user use the same controller instance)

---

Some reading:

• http://docs.spring.io/spring/docs/current/spring-framework-reference/html/beans.html
• http://www.oracle.com/technetwork/java/codeconventions-135099.html

Answer 2

I dont know JPA but before you use "employeeRepository.save(em);" dont you need to make a new instance of the class "EmployeeRepository" before you use the function in the class? I can see you declare the class at the top as private EmployeeRepository employeeRepository;

But cant see where you create an instance of it and if you don't it will give you a nullpointer exception error when you try using the function save.

for example:

EmployeeRepository employeeRepository =  new EmployeeRepository ();
employeeRepository.save(em);

If this does not solve your answer please post more detail of function "save"