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Creating a RESTful web service

In this section, you will learn how to create a RESTful web service. The concepts explained earlier in this chapter will be used.

The following are some of the key aspects of creating a RESTful web service. Let's take the example of retrieving the doctors' list based on the specialties, location, and so on.

  • Create a controller representing the RESTful endpoint: In the following code, note the usage of the @RestController annotation, which is used to represent the annotation @Controller and @ResponseBody. The controller has a method, searchDoctor, for handling the request represented using the URL such as /doctors?location=xxx&speciality=yyy. Note the @RequestMapping annotation and its attributes, especially, "produces", which signifies the fact that the output sent to the user will be in the JSON format.
    @RestController
public class DoctorSearchController {

@Autowired
DoctorService docService;

@RequestMapping(value="/doctors", method=RequestMethod.GET,
produces="application/json")

public DoctorList searchDoctor(
@RequestParam(value="location", required=false) String location,
@RequestParam(value="speciality", required=false) String speciality)
{
DoctorList docList = docService.find(location, speciality);
return docList;
}
}

The following is how the DoctorService implementation may look like:

    @Service
public class DoctorServiceImpl implements DoctorService {

@Autowired
private DoctorDAO doctorDAO;

@Override
public List<Doctor> findByLocationAndSpeciality(String location, String
speciality) {
return doctorDAO.findByLocationAndSpeciality(location, specialityCode);
}
}

The following is how the DoctorDAO implementation may look like:

    @Repository
@Transactional
public class DoctorDAOImpl implements DoctorDAO {

private SessionFactory sessionFactory;

@Autowired
public DoctorDAOImpl(SessionFactory sessionFactory) {
this.sessionFactory = sessionFactory;
}

@Override
public List<Doctor> findByLocationAndSpeciality(String location, String speciality) {
Session session = this.sessionFactory.getCurrentSession();
TypedQuery<Doctor> query = session.getNamedQuery("findByLocationAndSpeciality");
query.setParameter("location", location);
query.setParameter("speciality", speciality);
List<Doctor> doctors = query.getResultList();
return doctors;
}
}
  • Create a RESTful API: For retrieving the list of doctors based on location and speciality, the URL could look like  http://localhost:8080/doctors?location=xxx&speciality=yyy.
  • Identify the method of processing incoming requests data: @RequestParam will be used to process the incoming requests data as mentioned in the preceding URL. In the previous code, note how @RequestParam is used for processing the value of both the location and the specialty parameter. The following code represents the same:
        public DoctorList searchDoctor(
@RequestParam(value="location", required=false)
String location,
@RequestParam(value="specialty", required=false)
String speciality) {
// Code goes here
}
  • Create a class representing ResponseBody: The return value is the DoctorList object, which consists of a list of Doctors. The following code represents the DoctorList object which is a list of the Doctor object:
    // The class representing the list of Doctor; Returned as a response
public class DoctorList {
private List<Doctor> doctors;

public DoctorInfo(List<Doctor> doctors) {
this.setDoctors(doctors);
}
public List<Doctor> getDoctors() {
return doctors;
}
public void setDoctors(List<Doctor> doctors) {
this.doctors = doctors;
}
}

The following represents the Doctor class which is returned as part of the response object:

    public class Doctor {

private String id;
private String firstName;
private String lastName;
private String specialityCode;

public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getSpecialityCode() {
return specialityCode;
}
public void setSpecialityCode(String specialityCode) {
this.specialityCode = specialityCode;
}
}
  • Client response: The client receives the response body in the JSON format. The following is a sample response which is returned by the execution of the preceding code:
    [{
"id": "doc1",
"firstName": "Calvin",
"lastName": "Hobbes",
"specialityCode": "pediatrics"
},
{
"id": "doc2",
"firstName": "Susan",
"lastName": "Storm",
"specialityCode": "cardiology"
}]
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