Short & Quick introduction to REST
REST stands for Representational State Transfer.It’s an is an architectural style which can be used to design web services, that can be consumed from a variety of clients. The core idea is that, rather than using complex mechanisms such as CORBA, RPC or SOAP to connect between machines, simple HTTP is used to make calls among them.
In Rest based design, resources are being manipulated using a common set of verbs.
To Create a resource : HTTP POST should be used
To Retrieve a resource : HTTP GET should be used
To Update a resource : HTTP PUT should be used
To Delete a resource : HTTP DELETE should be used
That means, you as a REST service developer or Client, should comply to above criteria, in order to be REST complained.
Often Rest based Web services return JSON or XML as response, although it is not limited to these types only. Clients can specify (using HTTP Accept header) the resource type they are interested in, and server may return the resource , specifying Content-Type of the resource it is serving. This StackOverflow link is a must read to understand REST in detail.
Sample code:
packagecom.websystique.springboot.controller;
importjava.util.List;
importorg.slf4j.Logger;
importorg.slf4j.LoggerFactory;
importorg.springframework.beans.factory.annotation.Autowired;
importorg.springframework.http.HttpHeaders;
importorg.springframework.http.HttpStatus;
importorg.springframework.http.ResponseEntity;
importorg.springframework.web.bind.annotation.PathVariable;
importorg.springframework.web.bind.annotation.RequestBody;
importorg.springframework.web.bind.annotation.RequestMapping;
importorg.springframework.web.bind.annotation.RequestMethod;
importorg.springframework.web.bind.annotation.RestController;
importorg.springframework.web.util.UriComponentsBuilder;
importcom.websystique.springboot.model.User;
importcom.websystique.springboot.service.UserService;
importcom.websystique.springboot.util.CustomErrorType;
@RestController
@RequestMapping("/api")
publicclassRestApiController {
publicstaticfinalLogger logger = LoggerFactory.getLogger(RestApiController.class);
@Autowired
UserService userService; //Service which will do all data retrieval/manipulation work
// -------------------Retrieve All Users---------------------------------------------
@RequestMapping(value = "/user/", method = RequestMethod.GET)
publicResponseEntity
List
if(users.isEmpty()) {
returnnewResponseEntity(HttpStatus.NO_CONTENT);
// You many decide to return HttpStatus.NOT_FOUND
}
returnnewResponseEntity
}
// -------------------Retrieve Single User------------------------------------------
@RequestMapping(value = "/user/{id}", method = RequestMethod.GET)
publicResponseEntity getUser(@PathVariable("id") longid) {
logger.info("Fetching User with id {}", id);
User user = userService.findById(id);
if(user == null) {
logger.error("User with id {} not found.", id);
returnnewResponseEntity(newCustomErrorType("User with id "+ id
+ " not found"), HttpStatus.NOT_FOUND);
}
returnnewResponseEntity
}
// -------------------Create a User-------------------------------------------
@RequestMapping(value = "/user/", method = RequestMethod.POST)
publicResponseEntity createUser(@RequestBodyUser user, UriComponentsBuilder ucBuilder) {
logger.info("Creating User : {}", user);
if(userService.isUserExist(user)) {
logger.error("Unable to create. A User with name {} already exist", user.getName());
returnnewResponseEntity(newCustomErrorType("Unable to create. A User with name "+
user.getName() + " already exist."),HttpStatus.CONFLICT);
}
userService.saveUser(user);
HttpHeaders headers = newHttpHeaders();
headers.setLocation(ucBuilder.path("/api/user/{id}").buildAndExpand(user.getId()).toUri());
returnnewResponseEntity
}
// ------------------- Update a User ------------------------------------------------
@RequestMapping(value = "/user/{id}", method = RequestMethod.PUT)
publicResponseEntity updateUser(@PathVariable("id") longid, @RequestBodyUser user) {
logger.info("Updating User with id {}", id);
User currentUser = userService.findById(id);
if(currentUser == null) {
logger.error("Unable to update. User with id {} not found.", id);
returnnewResponseEntity(newCustomErrorType("Unable to upate. User with id "+ id + " not found."),
HttpStatus.NOT_FOUND);
}
currentUser.setName(user.getName());
currentUser.setAge(user.getAge());
currentUser.setSalary(user.getSalary());
userService.updateUser(currentUser);
returnnewResponseEntity
}
// ------------------- Delete a User-----------------------------------------
@RequestMapping(value = "/user/{id}", method = RequestMethod.DELETE)
publicResponseEntity deleteUser(@PathVariable("id") longid) {
logger.info("Fetching & Deleting User with id {}", id);
User user = userService.findById(id);
if(user == null) {
logger.error("Unable to delete. User with id {} not found.", id);
returnnewResponseEntity(newCustomErrorType("Unable to delete. User with id "+ id + " not found."),
HttpStatus.NOT_FOUND);
}
userService.deleteUserById(id);
returnnewResponseEntity
}
// ------------------- Delete All Users-----------------------------
@RequestMapping(value = "/user/", method = RequestMethod.DELETE)
publicResponseEntity
logger.info("Deleting All Users");
userService.deleteAllUsers();
returnnewResponseEntity
}
}
publicclassCustomErrorType {
privateString errorMessage;
publicCustomErrorType(String errorMessage){
this.errorMessage = errorMessage;
}
publicString getErrorMessage() {
returnerrorMessage;
}
}