Today, just a short code snippet. How to add a header to the ‘RestTemplate’ on Spring.

public class HeaderRequestInterceptor implements ClientHttpRequestInterceptor {

    private final String headerName;
    private final String headerValue;

    public HeaderRequestInterceptor(String headerName, String headerValue) {
        this.headerName = headerName;
        this.headerValue = headerValue;
    }

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        request.getHeaders().set(headerName, headerValue);
        return execution.execute(request, body);
    }
}

Now, we add it to our ‘RestTemplate’:

List<ClientHttpRequestInterceptor> interceptors = new ArrayList<ClientHttpRequestInterceptor>();
interceptors.add(new HeaderRequestInterceptor("X-Custom-Header", "<custom_value>"));

RestTemplate restTemplate = new RestTemplate();
restTemplate.setInterceptors(interceptors);

And, that’s all.

Just an extra side note. As of Spring Framework 5, a new HTTP client called ‘WebClient’ has been added. It is assumed that ‘RestTemplate’ will be deprecated at some point. If we are starting a new application, specially if you are using the ‘WebFlux’ stack, it will be a better choice to use the new version.