POST API

1 minute read

Post Mapping with request Body

Code sample for a POST request using Spring Boot. Sample code converts Temperature from Farenheit to Celcius.

In all the examples below, ResponseEntity.ok() method is used, that takes in the response body as its argument.

public static <T> ResponseEntity<T> ok(T body)
Scenario 1

Convert the temperature given in Request Body of POST call.

POST : http://localhost:8100/temperature-converter/value

Request Body :

{
    "value":"10"
}

Controller:

@RequestBody Map<String, Double> value captures the request body in a map and is extracted using the map key.

ResponseEntity<Double> to return a Double Value

@PostMapping(path = "/temperature-converter/value")
public ResponseEntity<Double> convertTemperature(@RequestBody Map<String, Double> value) {
    return ResponseEntity
            .status(HttpStatus.OK)
            .body(temperatureConvertorService.convertTemperatureValue(value.get("value")));    
}
Scenario 2:

Convert List of temperatures given in Request Body of POST call and return converted List

POST : http://localhost:8100/temperature-converter/values

Request Body :

{
    "values":["10","12.5","50","100"]
}

Controller:

@PostMapping(path = "temperature-converter/values")
    public ResponseEntity<List<Double>> convertTemperatures(@RequestBody Map<String, List<Double>> body) {
        //Extract the List out of the Request body
        List<Double> temperatures = body.get("values");
        return ResponseEntity.ok(temperatureConvertorService.convertTemperatureValues(temperatures));
    }

Notice the response entity returning a List of converted temperatures.

Scenario 3:

Convert List of temperatures given in Request Body with the Temperature units of POST call and return converted List

POST : http://localhost:8100/temperature-converter/

Request Body :

{
    "from":"F",
    "to":"C",
    "values":["10","12.5","50","111"]
}

Controller: This time, the request body is directly mapped with the Object

@PostMapping(path = "temperature-converter/")
    public ResponseEntity<List<Double>> convertTemperaturesUsingObject(@RequestBody Temperature value) {
        return ResponseEntity.ok(temperatureConvertorService.convertTemperatureValues(value.getValues()));
    }

POST - Create Data

Controller Class

//Add a new User
@PostMapping("/users")
public void addNewUser(@RequestBody User user){
    userDAOService.save(user);

}

DAOService Class

//Save a new User
public void save(User user) {
    if(user.getId() == null){
        user.setId(++usersCount);
    }
    users.add(user);
}

In Postman, create a POST call

/api/hardCodedData/users

with Request Body - resembling User class

{
"name": "Kid",
"dob": "2019-12-08T01:19:11.760+0000"
}

Returns 200 OK

POST Method enhancement

to return HTTP Status Code and URI

//Add a new User
@PostMapping("/users")
public ResponseEntity<Object> addNewUser(@RequestBody User user){
    User savedUser = userDAOService.save(user);

    //Send the URI of the saved Object
    URI location = ServletUriComponentsBuilder
            .fromCurrentRequest()
            .path("/{id}")
            .buildAndExpand(savedUser.getId()).toUri();

    return ResponseEntity.created(location).build();
}

Returns 201 Created

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