Spring rest exception handling

When we call a rest service with bad end points then it will throw an exception what will show lots of ugly information from the server . So we can modify  the exception information by developing our own custom exception.

lets see the practical example-

1. Creating our custom exception response pojo class that we want to sent back to the client.

public class StudentErrorResponse{

private int status;

private String message;

private long timestamp;

public StudentErrorResponse(int status,String message,long timeStamp){

        this.status = status;

        this.message = message;

        this.timeStamp = timeStamp;

    }

//Appropriate getter and setter for the properties

}

Now let's create our custom exception class.

public class StudentNotFound extends RuntimeException{

public StudentNotFound(String message,Throwable cause){

super(message,cause);

}

public StudentNotFound(String message){

super(message);

}

public StudentNotFound(String cause){

super(cause);

}

}

Now lets  throws exception from our rest controller if student is not found,

@RestController

@RequestMapping("/api")

public class StudentRestController{

 private List<Student> students ;

@PostConstruct  //defining @PostConstruct will load data only once after class has been loaded .

public void loadData(){

        students = new ArrayList<Student>();

        students.add(new Student("lokman","hossain"));

        students.add(new Student("sadia","muna"));

}

@GetMapping("/students")

public List<Student> getStudents(){

  return students;

    }

@GetMapping("/students/{studentId}")

public Student getStudent(@PathVariable int studentId){

if((studentId>students.size() )|| (studentId<0))

    throw new StudentNotFound("Student not found with the given student id:"+studentId);

return students.get(studentId);

}

//Adding exception handler

@ExceptionHandler

public ResponseEntity<StudentErrorResponse> handleException(StudentNotFound  exc){

StudentErrorResponse errorResponse = new StudentErrorResponse();

errorResponse.setStatus(HttpStatus.Not_found.value());

errorResponse.setMessage(exc.getMessage());

errorResponse.setTimeStamp(System.currentTimeMillis());

return new ResponseEntity<>(errorResponse, HttpStatus.NOT_FOUND);// will return a json .jackson                                                                                                                           will convert the pojo to json .

}

What if the user request using character in request parameter without giving integer value . then server again will show an ugly message .so we should handle it . so lets create another exception handler ..

@ExceptionHandler

public ResponseEntity<StudentErrorResponse> handleException(Exception ex){

StudentErrorResponse errorResponse = new StudentErrorResponse();

errorResponse.setStatus(HttpStatus.BAD_REQUEST.value());

errorResponse.setMessage(exc.getMessage());

errorResponse.setTimeStamp(System.currentTimeMillis());

return new ResponseEntity<>(errorResponse, HttpStatus.BAD_REQUEST);

}

}