Implementing the POST Method to create User Resource
In the previous few steps, we have created simple RESTful services. In this section, we will use the POST method to post the user resource for the specific URI "/users."
Here we are using two annotations, @RequestBody and @PathMapping.
The @RequestBody annotation maps body of the web request to the method parameter. The body of the request is passed through an HttpMessageConverter. It resolves the method argument depending on the content type of the request. Optionally, automatic validation can be applied by annotating the argument with @Valid.
In the following example, when we pass the @RequestBody annotation in the createUser() method, it maps to the user parameter.
The @PathMapping annotation is the specialized version of the @RequestMapping annotation which acts as a shortcut for @RequestMapping(method=RequestMethod=POST). @PostMapping method handles the Http POST requests matched with the specified URI.
Let's create a user resource and post that resource through the POST method.
Step 1: Open UserResource.java and add @PostMapping("/user").
Step 2: Create a method createUser() and pass the User class's object as the body of the web.
Step 3: Save the created user.
When we refresh the page it returns the get request. But we need to send POST request. We can send POST request through REST client. REST client is a client that is designed to use a service (RESTful) from a server.
Lets' see how to use the REST client.
Step 4: Download the Postman from https://www.getpostman.com/downloads/.
Or add Google Chrome extension in the browser https://bit.ly/1HCOCwF.
Step 5: Launch the Postman and Signup. Create a user name. Here we have created user name javatpoint and clicked on Submit button. Consider the below image:
Step 6: First, we check for the GET request. Type the URL http://localhost:8080/users/1 in the address bar and click on the Send button. It returns the detail of the first user.
Step 7: Now we send a POST request.
- Change the method to the POST.
- Copy the body of the response coming from "/users/1".
- Click on Body tab. Now we create a body for the POST request.
- Choose the raw option. It creates a raw request.
- Paste the copied content.
- Remove the id because it increments automatically.
- Change the "name": "Thomas".
- Instead of Text we are sending the data in the JSON format. So select JSON (application/json).
- Type the URL http://localhost:8080/users and click on the Send button.
- Click on the Get request on the left side of the window.
- Now we will send a Get request again, so change the URL http://localhost:8080/users and click on the Send button. It displays all the users, including which we have created.
Enhancing POST Method to Return Correct HTTP Code and Status Location
In this section, we will return the status (Created) and URI ("/users/6") of the user recourse which we have created.
The ResponseEntity is a class which extends HttpEntity and HttpStatus class. It is defined in org.springframework.http.RequestEntity.
- It is used in RestTemplate and @Controller methods.
- It is used as parameter in getForEntity() and exchange() method.
- It is also used in Spring MVC, as a parameter in a @Controller method.
created() method of RequestEntity Class
The created() method is the static method of RequestEntity class. It creates a new builder with a CREATED status and a location header set to the given URI.
Parameter: It accepts the location URI as a parameter.
Returns: It returns the created builder.
All Http status codes are Enum constant, which is defined in the HttpStatus class.
The ServletUriComponentsBuilder is a class which is defined in org.springframework.web.servlet.support.ServletUriComponentsBuilder. It extends UriComponentsBuilder class. It has additional static factory methods to create a link based on the current HttpServletRequest.
It is similar to fromRequest(HttpServletRequest) method except the request is obtained through RequestContextHolder.
The path() is the method of UriComponentsBuilder class. It appends the given path to the existing path of this builder. The given path may contain URI template variable.
Parameter: It accepts a path as a parameter.
Returns: It returns the UriComponentsBuilder.
It builds UriComponents instance and replaces URI template variables with the values obtained from an array. It is the shortcut method which combines calls to build() and then UriComponents.expand(Object... uriVariableValues).
Parameter: It accepts the URI variable values as a parameter.
Returns: It returns the URI components with extended values.
It builds UriComponents instance from the various components contained in the builder.
Parameter: It does not accept any parameter.
Returns: It returns the Uri Components.
Let's see how to return the status of the created resource and how to set URI of the created resource in the response.
Step 1: Create a method that creates a user resource and returns the ResponseEntity.
Step 2: Now open REST client Postman and create a POST request.
Step 3: Click on the POST request under the History tab.
Step 4: Click on the Body tab and change the user name to James.
Step 5: Ensure that you have selected JSON (application/json) media type.
Step 5: Click on the Send button.
On the right-hand side of the window, we can see the Status: 201 Created. It means resource has been properly created.
Step 6: Now click on the Headers tab to see the location. Location is the URI of the created resource. It shows the location of the created user James that is "/users/6".
If the client wants to know where the user resources was created, just pick up the location from the header of the response.