Post request via RestTemplate in JSON

java

rest-template

json-parsing

exception-handling

byNikita Barsukov·Mar 2, 2025

To execute a POST request with JSON using RestTemplate, follow these steps:

Instantiate a new RestTemplate object
Set your headers to MediaType.APPLICATION_JSON
Wrap your JSON string in a HttpEntity
Lastly, call the postForEntity method with the necessary parameters: url, entity, and response type.

RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
String json = "{\"key\":\"value\"}"; // Just a friendly JSON saying "Hello!" to your API
HttpEntity<String> entity = new HttpEntity<>(json, headers);
ResponseEntity<String> response = restTemplate.postForEntity("http://example.com/api", entity, String.class); // Knock, knock. Who's there? It's me, your POST request!
String result = response.getBody(); // "Hello, it's the Server. I've received your letter!"

Detailed walkthrough: Improve by knowing the whys and hows

Understanding the basic details of RestTemplate and the customizable options available can significantly enhance your REST API interactions. Let's discuss some finer points to improve your POST requests:

Personalizing message converters

Dealing with complex JSON structures? Register a custom message converter:

RestTemplate restTemplate = new RestTemplate();
MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
restTemplate.getMessageConverters().add(converter); //"I like your style, JSON! Let's dance together!"

The Art of Exception Handling

POST requests fail, and that's a given. Use exception handling to prepare a useful error response:

try { // Dare to try!
    ResponseEntity<String> response = restTemplate.postForEntity(url, entity, String.class);
   // process the response - data alchemy, anyone?
} catch (HttpClientErrorException | HttpServerErrorException e) {
    // Not you again, HTTP errors!
} catch (RestClientException e) {
    // Unknown exceptions, the unwelcome guests
}

Log it or slog it

Debugging can be frustrating! But smart developers ensure their requests and responses are logged to make troubleshooting easier.

restTemplate.getInterceptors().add(new RequestResponseLoggingInterceptor()); //"Are you okay, Http Request? Let me take a look."

Prepared for the server?

Remember, the server needs to be capable of handling your media type (application/json). Prevent receiving those dreaded 415 Unsupported Media Type errors:

Cross-check the server's API documentation.
Check your requests using Postman or curl.

Advanced concepts: Unleash the power of RestTemplate

Tips from veterans to make your RestTemplate use even more efficient:

Turbocharged JSON parsing

High traffic on your application? Consider using Jackson or Gson for faster JSON parsing:

ObjectMapper objectMapper = new ObjectMapper(); //"I've a map for JSON treasure!"
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter(objectMapper));  // "Take a hike, slow parsing! Speed is the new swag!"

Resilient like a phoenix

Incorporate error handling, retry policies, and circuit breakers for robust RESTful communication.

Secure transmissions

Use HTTPS and ClientHttpRequestInterceptors for secure, confidential data exchange.

Practical use-cases: Hit the bullseye

Every situation calls for a slightly different solution. Let's see how to handle some standard scenarios with RestTemplate.

Posting raw JSON strings

When dealing with raw JSON strings, remember to escape all double quotes.

String rawJson = "{\"key\": \"value\"}"; 
// Guess what's the JSON's favorite dance style? Esc-ape!

Iterative testing

Iteratively test your RestTemplate configurations. Write unit tests for different scenarios.

Handling large data

Working with bulk data? Utilize the power of streaming for efficient request and response processing.

explain-codes / Java / Post request via RestTemplate in JSON

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Detailed walkthrough: Improve by knowing the whys and hows Advanced concepts: Unleash the power of RestTemplate Practical use-cases: Hit the bullseye