Rest Template in Java

  RestTemplate :

1) Why do we need RestTemplate? 

==> To communicate with different services in single application.

Create Resttemplate object:

// create an instance of RestTemplate

RestTemplate restTemplate = new RestTemplate();

2) Different methods of RestTemplate.

exchange()

<http_method>ForEntity      ex    getForEntity(),postForEntity()

<http_method>ForObject        ex    getForObject(),postForObject()

HttpPost Api with parameters:                                         Returns

PostForObject(url,request,classType);                         ResponseBody

PostForEntity(url,request,responseType);                    Response status,header,body

PostForLocation(url,request,responseType);                Only Location of the created resources.

exchange(url,httpmethod,request,responseType);

execute(url,httpmethod,request,responseType);

To Posting Json data:

PostForObject(url,request,classType);                         ResponseBody

PostForEntity(url,request,responseType);                    Response status,header,body

PostForLocation(url,request,responseType);                Only Location of the created resources.

Sending Header with RestTemplate

To send the request headers with the request ,we need to create an HtpEntity object,set Headers and post it to API.

To make a Post request with the JSON request body, we need to set the contentType request header to application/json.

Example

// request url String url = "https://reqres.in/api/login";

// create headers HttpHeaders headers = new HttpHeaders(); headers.setContentType(MediaType.APPLICATION_JSON); headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));

// build the request HttpEntity request = new HttpEntity(headers);

// send POST request ResponseEntity<String> response = restTemplate.postForEntity(url, request, String.class);

// check response
if (response.getStatusCode() == HttpStatus.OK) {
    System.out.println(" Post Data Successful");
} else {
    System.out.println("Failed");
}

POST Request with Response Mapped to Java Object:

// request url String url = "https://jsonplaceholder.typicode.com/posts"; // create an instance of RestTemplate RestTemplate restTemplate = new RestTemplate(); // create headers HttpHeaders headers = new HttpHeaders(); headers.setContentType(MediaType.APPLICATION_JSON); headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON)); // create a post object Post post = new Post(101, 1, "Spring Boot 101", "A powerful tool for building web apps."); // build the request HttpEntity<Post> request = new HttpEntity<>(post, headers); // send POST request ResponseEntity<Post> response = restTemplate.postForEntity(url, request, Post.class); // check response if (response.getStatusCode() == HttpStatus.CREATED) { System.out.println("Post Created"); System.out.println(response.getBody()); } else { System.out.println("Request Failed"); System.out.println(response.getStatusCode()); }

Hope you learned something new today.

Happy Learning :)

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