select json format spring mvc

package org.javacodegeeks.webservices.rest.ticket.endpoint;
 
import java.util.List;
 
import org.javacodegeeks.webservices.rest.ticket.domain.Comment;
import org.javacodegeeks.webservices.rest.ticket.domain.Ticket;
import org.javacodegeeks.webservices.rest.ticket.service.TicketService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
 
@RestController
public class TicketEndpoint {
 
    @Autowired
    private TicketService ticketService;
 
    // --------------------------------------------
    // CRUD OPERATIONS FOR PARENT RECORDS (TICKETS)
 
    @PostMapping("/tickets")
    public Ticket createTicket(@RequestBody Ticket ticket) {
        Ticket savedTicket = ticketService.createTicket(ticket);
        return savedTicket;
    }
 
    @GetMapping("/tickets")
    public List getAllTickets() {
        return ticketService.findAll();
    }
 
    @GetMapping("/tickets/{id}")
    public Ticket getTicket(@PathVariable long id) {
        return ticketService.findTicket(id);
    }
 
    @PutMapping("/tickets/{id}")
    public Ticket changeTicket(@PathVariable long id, @RequestBody Ticket ticket) {
        return ticketService.updateTicket(id, ticket);
    }
 
    @DeleteMapping("/tickets/{id}")
    public String deleteTicket(@PathVariable long id) {
        ticketService.deleteById(id);
        return String.format("Ticket id #%d successfully deleted", id);
    }
 
    // --------------------------------------------
    // CRUD OPERATIONS FOR CHILD RECORDS (COMMENTS)
 
    @PostMapping("/tickets/{id}/comments")
    public Ticket createComment(@PathVariable long id, @RequestBody Comment comment) {
        return ticketService.createComment(id, comment);
    }
 
    @GetMapping("/tickets/{id}/comments")
    public List getAllComments(@PathVariable long id) {
        return ticketService.findAllComments(id);
    }
 
    @GetMapping("/tickets/comments/{id}")
    public Comment getComment(@PathVariable long id) {
        return ticketService.findComment(id);
    }
 
    @PutMapping("/tickets/comments/{id}")
    public Comment changeComment(@PathVariable long id, @RequestBody Comment comment) {
        return ticketService.updateComment(id, comment);
    }
 
    @DeleteMapping("/tickets/comments/{id}")
    public String deleteComment(@PathVariable long id) {
        ticketService.deleteCommentById(id);
        return String.format("Comment id %d successfully deleted", id);
    }
}