Spring Boot - RestTemplate PATCH request fix

 

In Spring Boot, you make a simple http request as below:

1. Define RestTemplate bean

@Bean
public RestTemplate restTemplate() {
   return new RestTemplate();
}

2. Autowire RestTemplate wherever you need to make Http calls

@Autowire
private RestTemplate restTemplate;

3. Use auto-wired RestTemplate to make the Http call

restTemplate.exchange("http://localhost:8080/users", HttpMethod.POST, httpEntity, String.class);

Above setup works fine for all Http calls except PATCH. The following exception occurs if you try to make a PATCH request as above

Exception:

I/O error on PATCH request for \"http://localhost:8080/users\": Invalid HTTP method: PATCH; nested exception is java.net.ProtocolException: Invalid HTTP method: PATCH

Cause:

Above exception happens because of the HttpURLConnection used by default in Spring Boot RestTemplate which is provided by the standard JDK HTTP library.

More on this at this bug

Fix:

This can be resolved by adding new HttpRequestFactory to the RestTemplate instance which can handle PATCH as below. Some HttpRequestFactories provided by different libraries(Spring, Apache Http) handle this PATCH as a PUT internally.

Code to add HttpRequestFactory to RestTemplate:

@Bean
public RestTemplate restTemplate() {
    RestTemplate restTemplate = new RestTemplate();
    HttpClient httpClient = HttpClientBuilder.create().build();
    HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);
    restTemplate.setRequestFactory(requestFactory);
    return restTemplate;
}

You can use any of the following HttpRequestFactory's as well if the associated libraries are used in your project:

OkHttpClientHttpRequestFactory  - OkHttp2
OkHttp3ClientHttpRequestFactory - OkHttp3
Netty4ClientHttpRequestFactory  - Netty4

Happy coding 👨‍💻