Как вернуть ответ в JSON формате

C:\Users\Sky>curl -H "Content-Type: application/json" -d "{\"domain\":\"amazon.kz\"}" localhost:8080/api/whois
Domain Name............: amazon.kz
 
Organization Using Domain Name
Name...................: Amazon.com, Inc.
Organization Name......: Amazon.com, Inc.
Street Address.........: Legal Dept. P.O. Box 81226
City...................: Seattle WA
State..................:
Postal Code............: 98108
Country................: US
 
Administrative Contact/Agent
Nick Handle............: HOSTERKZ-76523
Phone Number...........: +1.2062664064
Fax....................: +1.2062667010
Email Address..........: admin@internationaladmin.com
 
Nameserver in listed order
 
Server.................: 3783652
Ip address.............: 185.98.6.6
Server.................: 3783652
Ip address.............: 104.131.219.250
Server.................: 3783652
Ip address.............: 92.38.225.176
 
Domain created: 1998-01-02 12:31:33
Last modified: 2013-03-16 10:52:31
Domain status: KAZNIC
Registrar created: HOSTER.KZ
Current Registrar: clientDeleteProhibited
Domain created: 1998-01-02 12:31:33
Last modified: 2013-03-16 10:52:31
Domain status: KAZNIC
Registrar created: HOSTER.KZ
Current Registrar: clientTransferProhibited

@RestController
@RequestMapping("api/whois")
public class DomainWhoIsController {
 
    @Autowired
    DomainRepository domainRepository;
 
    @Autowired
    ContactsRepository contactsRepository;
 
    @Autowired
    HostRepository hostRepository;
 
    @Autowired
    StatusRepository statusRepository;
 
    @PostMapping
    public String whoIs(@RequestBody Request request) {
        System.out.println(request);
        DomainInfo domainInfo = domainRepository.findDomainInfo(request.getDomain());
        ContactInfo contactInfo = contactsRepository.findContactInfo(request.getDomain());
        List<HostInfo> hostInfo = hostRepository.findHostInfo(request.getDomain());
        List<StatusInfo> statusInfo = statusRepository.findStatusInfo(request.getDomain());
 
        return report(domainInfo, contactInfo, hostInfo, statusInfo);
    }
 
    private String report(DomainInfo domainInfo, ContactInfo contactInfo, List<HostInfo> hostInfo, List<StatusInfo> statusInfo) {
        StringBuffer sb = new StringBuffer();
        sb
                .append("Domain Name............: ").append(domainInfo.getDomainName()).append(System.lineSeparator())
                .append(System.lineSeparator())
                .append("Organization Using Domain Name").append(System.lineSeparator())
                .append("Name...................: ").append(domainInfo.getName()).append(System.lineSeparator())
                .append("Organization Name......: ").append(domainInfo.getOrganizationName()).append(System.lineSeparator())
                .append("Street Address.........: ").append(domainInfo.getStreetAddress()).append(System.lineSeparator())
                .append("City...................: ").append(domainInfo.getCity()).append(System.lineSeparator())
                .append("State..................: ").append(domainInfo.getState()).append(System.lineSeparator())
                .append("Postal Code............: ").append(domainInfo.getPostalCode()).append(System.lineSeparator())
                .append("Country................: ").append(domainInfo.getCountry()).append(System.lineSeparator())
                .append(System.lineSeparator())
                .append("Administrative Contact/Agent").append(System.lineSeparator())
                .append("Nick Handle............: ").append(contactInfo.getHandle()).append(System.lineSeparator())
                .append("Phone Number...........: ").append(contactInfo.getVoice()).append(System.lineSeparator())
                .append("Fax....................: ").append(contactInfo.getFax()).append(System.lineSeparator())
                .append("Email Address..........: ").append(contactInfo.getEmail()).append(System.lineSeparator())
                .append(System.lineSeparator())
                .append("Nameserver in listed order").append(System.lineSeparator())
                .append(System.lineSeparator());
 
        hostInfo.forEach(hInfo -> sb
                .append("Server.................: ").append(hInfo.getDomain()).append(System.lineSeparator())
                .append("Ip address.............: ").append(hInfo.getIpaddr()).append(System.lineSeparator())
        );
 
        sb.append(System.lineSeparator());
 
        statusInfo.forEach(sInfo -> sb
                .append("Domain created: ").append(sInfo.getCreated()).append(System.lineSeparator())
                .append("Last modified: ").append(sInfo.getUpdated()).append(System.lineSeparator())
                .append("Domain status: ").append(sInfo.getStatus()).append(System.lineSeparator())
                .append("Registrar created: ").append(sInfo.getRegistarcr()).append(System.lineSeparator())
                .append("Current Registrar: ").append(sInfo.getRegistrar()).append(System.lineSeparator())
        );
 
        return sb.toString();
    }
}