Handle Spring REST separated Frontend/backend post request - spring

Question

I'm trying to develop a RESTful webservice with Spring using 2 different projects for backend/webservice and frontend.
In the backend project I implemented the model
#Entity
#Table(name="user")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id_user", nullable = false)
private String id;
#Column(name = "username", nullable = false)
private String username;
#Column(name = "firstname", nullable = false)
private String firstname;
#Column(name = "lastname", nullable = false)
private String lastname;
#Column(name = "password", nullable = false)
private String password;
#Column(name = "email", nullable = false)
private String email;
#Column(name = "own_printer", nullable = false)
private Boolean ownsPrinter;
// Getters Setters...
}
There is also a UserDAO class to access database (through Hibernate 4) and a UserManager for business processes. And then a UserController:
#RestController
public class UserController {
private UserService userService ;
#RequestMapping(value = "/listusers")
List<User> getAllUser() {
Application.context = new ClassPathXmlApplicationContext("applicationContext.xml");
userService = (UserService) Application.context.getBean("userService");
List<User> users = userService.getUsers();
return users;
}
#RequestMapping(value = "/user/{userid}")
User getUserById(#PathVariable("userid") String userId) {
Application.context = new ClassPathXmlApplicationContext("applicationContext.xml");
userService = (UserService) Application.context.getBean("userService");
User user = userService.getUserById(userId);
return user;
}
#RequestMapping(value = "/user/add")
#ResponseBody
User signUpUser(#RequestBody User user ) {
// Don't really know what to do...
userService = (UserService) Application.context.getBean("userService");
return user;
}
}
And now for the frontend projects I implemented the same User class. And I wrote a UserDAO UserManager and UserController classes:
//UserDAO.java
#Repository("userDAO")
public class UserDAOImpl implements UserDAO{
#Override
public ArrayList<User> getUsers() {
//User[] users = new RestTemplate().getForEntity(WebService.getWebServiceUrl() + "users", User[].class).getBody();
ArrayList<User> user = new RestTemplate().getForEntity(WebService.getWebServiceUrl() + "listusers", ArrayList.class).getBody();
return (user);
//return Arrays.asList(users);
}
#Override
public User getUserById(String userId) {
User user = new RestTemplate().getForEntity(WebService.getWebServiceUrl() + "user/" + userId, User.class).getBody();
return user;
}
#Override
public void insertUser(User user) {
// doesn't work
RestTemplate template = new RestTempl ate();
template.postForObject(WebService.getWebServiceUrl() + "user/add",user, String.class);
System.out.println(user.toString());
}
}
//UserController.java
#Controller
public class UserController {
private static final Logger logger = LoggerFactory.getLogger(UserController.class);
private UserService userService = new UserServiceImpl();
#RequestMapping(value = "/listusers", method = RequestMethod.GET)
public String listUsers(#RequestParam(required=false)Locale locale, Model model) {
logger.info("Users page", locale);
ArrayList<User> users = userService.getUsers();
model.addAttribute("users", users);
return "listusers";
}
#RequestMapping(value = "/user/{user_id}", method = RequestMethod.GET)
public String singleUser(#RequestParam(required=false)Locale locale,
Model model,HttpServletRequest request, #RequestParam String id) {
logger.info("User page", locale);
User user = userService.getUserById(id);
model.addAttribute("user", user);
return "user";
}
#RequestMapping(value = "/signup", method = RequestMethod.GET)
public String listPersons(Model model) {
model.addAttribute("user", new User());
return "signup";
}
//For add and update person both
#RequestMapping(value= "/user/add", method = RequestMethod.POST)
#ResponseBody
public void saveUser(Model model, #ModelAttribute("user") User u){
RestTemplate rt = new RestTemplate();
rt.getMessageConverters().add(new MappingJacksonHttpMessageConverter());
rt.getMessageConverters().add(new StringHttpMessageConverter());
String uri = new String(WebService.getWebServiceUrl() + "user/add");
User user = new User();
user = u;
User returns = rt.postForObject(uri, u, User.class);
}
}
The get requests work: I get to display my list of users. But my problem is that I can't get to pass data from the frontend part to the backend webservice part with a post request... I'have been trying several solutions but I think there is something wrong with something else.
I'm kinda new in the world of JavaEE applications. Can someone help me or guide me to a solution ?

Answer 1

In the Frontend UserDAO:
public ArrayList<User> getUsers() {
ArrayList<User> user = new RestTemplate().getForEntity(WebService.getWebServiceUrl() + "listusers", ArrayList.class).getBody();
return (user);
}
This code allows to request the server through the uri "/listuser". On the frontEnd UserController you can see the function that call getUsers():
#RequestMapping(value = "/listusers", method = RequestMethod.GET)
public String listUsers(#RequestParam(required=false)Locale locale, Model model) {
logger.info("Users page", locale);
ArrayList<User> users = userService.getUsers();
model.addAttribute("users", users);
return "listusers";
}
And then in the backend the function that route this url:
#RequestMapping(value = "/listusers")
List<User> getAllUser() {
Application.context = new ClassPathXmlApplicationContext("applicationContext.xml");
userService = (UserService) Application.context.getBean("userService");
List<User> users = userService.getUsers();
return users;
}
After this, teh backend UserDAO class access to database.

Answer 2

You may want to take a look at the URL you are posting to at the frontend. You are using the same URL for posting to frontend (UserDAO) and backend (UserController) : WebService.getWebServiceUrl()
[EDIT]
You have two POST services as /user/add/ , If you are exposing them on the same url, it is a conflict. Probably your backend will be hosted on another port or another server. You should use that url to hit the backend service from frontend.
[EDIT 2]
Yes for listusers you are not making a REST call from frontend. You are calling the JAVA API userService. But for add user, you are making a REST call from frontend to backend once again