CODEWITHSUNDEEP
ajaxspring-mvc
Igmer Rodriguez
Igmer Rodriguez

Reputation: 172

How return a empty JSON in Spring MVC?

I'm using ajax with GET method, I'm waiting receive a JSON but sometime the response is null and get the error:

SyntaxError: Unexpected end of JSON input

ajax:

 $(document).ready(function() {
    
    $("#form_data").submit(function(e) {
        e.preventDefault()          
        var expediente = $('#expediente').val();
        $.ajax({
            url : 'buscarPaciente' + '?expediente=' + expediente,
            dataType : "json",
            type : "GET",
            contentType : 'application/json',
            mimeType : 'application/json',
            success : function(data) {
                console.log(data.nombre);
            },
            error : function(xhr, status, error) {
                console.log(error)
            }
        });

    })
});

in the controller:

@RequestMapping(value="/buscarPaciente", method = RequestMethod.GET)
public @ResponseBody MntPaciente 
buscarPaciente(@RequestParam("expediente") String expediente) {         
    MntPaciente mntPaciente = servicePx.findByexpediente(expediente);
    if (mntPaciente!= null) {
        return mntPaciente;         
    }
    return null; // Should I return an empty json?  how?        
}

Upvotes: 0

Views: 3206

Answers (1)

Ken Chan
Ken Chan

Reputation: 90507

There are several ways to do it. The first is to configure the JSON library that used to serialise JSON .In case of Jackson , you can use @JsonInclude to exclude all the empty properties not to serialise and just return an empty MntPaciente :

@JsonInclude(Include.NON_EMPTY)
public class MntPaciente {

}

public @ResponseBody MntPaciente buscarPaciente(@RequestParam("expediente") String expediente) {

    ....
    return new MntPaciente();  
}

To apply globally rather to configure for each object , you could use 

ObjectMapper om = new ObjectMapper();
om.setSerializationInclusion(Include.NON_EMPTY);

The other way is to change the controller method to return ResponseEntity and directly return a empty JSON string :

public @ResponseBody ResponseEntity buscarPaciente(@RequestParam("expediente") String expediente) {

      if (mntPaciente!= null) {
         return ResponseEntity.of(mntPaciente);       
      }else{
         return ResponseEntity.of("{}");
       }
}

Upvotes: 1

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