JSON parse error: Cannot deserialize instance of `java.lang.Long

Question

I am using Spring boot I try to create a new Student.

@RequestMapping(path="/student/create", method=RequestMethod.POST)<br>
     public ResponseEntity<String> createStudent(@RequestBody Long nummer, String firstname, String lastname){<br>
      service.createStudent(matrikelnummer, vorname, nachname);<br>
      return new ResponseEntity<String>("gut gemacht", HttpStatus.OK);

Here my RequestBody with RESTCLIENT

{"nummer":15557,"firstname":"toti","lastname":"Innna"}

I have this Error:

{"timestamp":"2019-12-20T19:41:30.083+0000","status":400,"error":"Bad Request","message":"JSON parse error: Cannot deserialize instance of java.lang.Long out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.lang.Long out of START_OBJECT token\n at [Source: (PushbackInputStream); line: 1, column: 1]","trace":"org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of java.lang.Long out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.lang.Long out of START_OBJECT token\n at [Source: (PushbackInputStream); line: 1, column: 1]\r\n\tat

Pieterjan Deconinck · Accepted Answer · 2019-12-20 20:06:29Z

4

In your example the mapper expects the body to present a Long object, but you pass it a Student object. This does not match, so it throws an exception.

It is not necessary to list all the fields of the students as separate method arguments, you can just pass a Student object as RequestBody argument. The object mapper will then try to resolve a Student instance from the provided JSON.

Example:

@RequestMapping(path="/student/create", method=RequestMethod.POST)
public ResponseEntity<String> createStudent(@RequestBody Student student){
    service.createStudent(student);
    return new ResponseEntity<String>("gut gemacht", HttpStatus.OK);
}

answered Dec 20, 2019 at 20:06

Pieterjan Deconinck

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3 Comments

berrows rachid Over a year ago

@Poeterjan Thank you first. But the problem is, I defined the method in my service class.

Pieterjan Deconinck Over a year ago

If you want to use the full JSON as a request body, you will need the Student object as parameter in the API. If you want to use different parameters instead, try to use @RequestParameter instead of RequestBody (for all parameters).

RobOhRob Over a year ago

or service.createStudent(student.getMatrikelnummer(), student.getVorname(), student.getNachname());

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