Spring Boot 3 - RestTemplate and GET method request with body (JSON payload)

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// --------------------------------------------------------------------------------
// Program.java file:
// --------------------------------------------------------------------------------

package com.dirask.example;

public class Program {

	public static void main(String[] args) throws Exception {

		MessageRequest messageRequest = new MessageRequest();

		messageRequest.setTitle("Invitation");
		messageRequest.setContent("Hi there!!!");

		ExtendedRestTemplate restTemplate = new ExtendedRestTemplate();
		MessageResponse messageResponse = restTemplate.getForObject("http://localhost/api/message/send", messageRequest, MessageResponse.class);  // <--- GET method request with body

		System.out.println("Result: " + messageResponse.getResult());
		System.out.println("Error:  " + messageResponse.getError());
	}
}

// See also:
//
//     1. https://dirask.com/snippets/Spring-Boot-3-RestTemplate-with-custom-HTTPS-SSL-certificate-1GM8Yp
//     2. https://dirask.com/snippets/Spring-Boot-3-RestTemplate-with-ignored-HTTPS-SSL-certificate-ignore-untrusted-certificates-1bQZJj



// --------------------------------------------------------------------------------
// ExtendedRestTemplate.java file (it allows to send GET requests with body):
// --------------------------------------------------------------------------------

package com.dirask.example;

import java.net.URI;
import java.util.List;
import java.util.Map;

import org.springframework.http.HttpMethod;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.lang.Nullable;
import org.springframework.web.client.HttpMessageConverterExtractor;
import org.springframework.web.client.RequestCallback;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.RestTemplate;

public class ExtendedRestTemplate extends RestTemplate {

	public ExtendedRestTemplate() {
		super();
	}

	public ExtendedRestTemplate(ClientHttpRequestFactory requestFactory) {
		super(requestFactory);
	}

	public ExtendedRestTemplate(List<HttpMessageConverter<?>> messageConverters) {
		super(messageConverters);
	}

	@Nullable
	public <T> T getForObject(URI url, @Nullable Object requestObject, Class<T> responseType) throws RestClientException {
		List<HttpMessageConverter<?>> messageConverters = super.getMessageConverters();
		RequestCallback requestCallback = super.httpEntityCallback(requestObject, responseType);
		HttpMessageConverterExtractor<T> responseExtractor = new HttpMessageConverterExtractor<>(responseType, messageConverters);
		return super.execute(url, HttpMethod.GET, requestCallback, responseExtractor);
	}

	@Nullable
	public <T> T getForObject(String url, @Nullable Object requestObject, Class<T> responseType, Object... uriVariables) throws RestClientException {
		List<HttpMessageConverter<?>> messageConverters = super.getMessageConverters();
		RequestCallback requestCallback = httpEntityCallback(requestObject, responseType);
		HttpMessageConverterExtractor<T> responseExtractor = new HttpMessageConverterExtractor<>(responseType, messageConverters);
		return super.execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
	}

	@Nullable
	public <T> T getForObject(String url, @Nullable Object requestObject, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
		List<HttpMessageConverter<?>> messageConverters = super.getMessageConverters();
		RequestCallback requestCallback = super.httpEntityCallback(requestObject, responseType);
		HttpMessageConverterExtractor<T> responseExtractor = new HttpMessageConverterExtractor<>(responseType, messageConverters);
		return super.execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
	}
}



// --------------------------------------------------------------------------------
// MessageRequest.java file (example class used to exchange data):
// --------------------------------------------------------------------------------

package com.dirask.example;

public class MessageRequest {

	private String title;
	private String content;

	public String getTitle() {
		return this.title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getContent() {
		return this.content;
	}

	public void setContent(String content) {
		this.content = content;
	}
}



// --------------------------------------------------------------------------------
// MessageResponse.java file (example class used to exchange data):
// --------------------------------------------------------------------------------

package com.dirask.example;

private class MessageResponse {

	public Boolean result;
	public String error;

	public Boolean getResult() {
		return this.result;
	}

	public void setResult(Boolean result) {
		this.result = result;
	}

	public String getError() {
		return this.error;
	}

	public void setError(String error) {
		this.error = error;
	}
}