How to display customized error response in REST API - spring

Question

My url is http://localhost:8090/employee/?emp_id=1551&name=
I am using Spring boot for designing REST application. I have used #RequestMapping and #RequestParam annotation for get resource. When I pass empty value to request parameter (for eg. name = ), I get below validation response(actual output section below).
However I wanted to override this output to display customized error response as below(expected section below).
How can I achieve this? How to avoid Spring's auto validation for input parameters in Get request?
Output
======
{
"timestamp": 1511144660708,
"status": 400,
"error": "Bad Request",
"message": "Required String parameter 'name' is not present",
"path": "/employee"
}
Expected
========
{
"errors":[
{
"id":"123144",
"detail": "invalid user input"
"status": "400"
}
]
}

Answer 1

Following sample code demonstrates how to customize error message for exception handling.
Create 2 POJOs for your customized response body.
Implement 1 method to catch the MissingServletRequestParameterException exception with #ExceptionHandler annotation for missing paramters.
Generate the response as you expected.
Class: ResponseProperty.java
public class ResponseProperty {
private int id;
private String detail;
private int status;
//getters and setters produced by IDE
}
Class: ResponsePOJO.java
public class ResponsePOJO {
List<ResponseProperty> errors;
public List<ResponseProperty> getErrors() {
return errors;
}
public void setErrors(List<ResponseProperty> errors) {
this.errors = errors;
}
}
Method: handleMethodArgumentTypeMismatch
#ExceptionHandler({ MissingServletRequestParameterException.class })
public ResponseEntity<Object> handleMethodArgumentTypeMismatch(MissingServletRequestParameterException ex) {
ResponseProperty property = new ResponseProperty();
property.setId(123144);
property.setDetail("invalid user input");
property.setStatus(400);
ResponsePOJO responsePOJO = new ResponsePOJO();
List<ResponseProperty> propertyList = new ArrayList<ResponseProperty>();
propertyList.add(property);
responsePOJO.setErrors(propertyList);
return new ResponseEntity<Object>(responsePOJO, HttpStatus.BAD_REQUEST);
}
If you visit the endpoint /employee without required parameter, then you are going to see the response as follows:
Http Response
{
"errors": [
{
"id": 123144,
"detail": "invalid user input",
"status": 400
}
]
}
Hope this helps you! :)
UPDATE
If you want to get the request ID from header named requestId for response, you can use WebRequest to get this information as follows:
#ExceptionHandler({ MissingServletRequestParameterException.class })
public ResponseEntity<Object> handleMethodArgumentTypeMismatch(MissingServletRequestParameterException ex,
WebRequest request) {
ResponseProperty property = new ResponseProperty();
property.setId(Integer.valueOf(request.getHeader("requestId")));
...
}