SpringBoot upgrade RestTemplateBuilder from 1.5.14 to 2.1.5

You don't need a builder here anymore as the supplier builds the ClientHttpRequestFactory on demand. Define the RequestFactorySupplier and the RestTemplateBuilder as beans.

    @Bean
    Supplier<ClientHttpRequestFactory> myRequestFactorySupplier() {
        return () -> {
            HttpClientBuilder clientBuilder = HttpClientBuilder.create();
            HttpClient httpClient = clientBuilder.build();
            HttpComponentsClientHttpRequestFactory requestFactory = 
                    new HttpComponentsClientHttpRequestFactory(httpClient);
            requestFactory.setConnectTimeout(5000);
            requestFactory.setReadTimeout(5000);
            requestFactory.setBufferRequestBody(false);
            return requestFactory;
        };
    }

    @Bean
    public RestTemplateBuilder restTemplateBuilder() {
        return new RestTemplateBuilder();
    }

Use the factory in the controller like this.

@RestController
public class TestController {

    private final RestTemplate restTemplate;

    public TestController(
            RestTemplateBuilder restTemplateBuilder,
            Supplier<ClientHttpRequestFactory> myRequestFactorySupplier
    ) {
            this.restTemplate = restTemplateBuilder                
                .requestFactory(myRequestFactorySupplier)
                .build();
    }

Of course you could also use a specialized class.

public class MyRequestFactorySupplier implements Supplier<ClientHttpRequestFactory> {

        @Override
        public ClientHttpRequestFactory get() {
            // Using Apache HTTP client.
            HttpClientBuilder clientBuilder = HttpClientBuilder.create();
            HttpClient httpClient = clientBuilder.build();
            HttpComponentsClientHttpRequestFactory requestFactory = 
                    new HttpComponentsClientHttpRequestFactory(httpClient);
            requestFactory.setBufferRequestBody(false); // When sending large amounts of data via POST or PUT, it is recommended to change this property to false, so as not to run out of memory.
            return requestFactory;
        }

}

using it in the controller as you proposed:

 public TestController(
     RestTemplateBuilder restTemplateBuilder,
     Supplier<ClientHttpRequestFactory> myRequestFactorySupplier
 ) {
     this.restTemplate = restTemplateBuilder
                .setConnectTimeout(Duration.ofMillis(5000))
                .setReadTimeout(Duration.ofMillis(5000))
                .requestFactory(new MyRequestFactorySupplier())
                .build();
 }

I have wrote detail notes on my github wiki page , please check sure will be helpful

• https://github.com/vaquarkhan/vaquarkhan/wiki/RestTemplate-vs-WebClient

Here is example :

        public String retrieveData(String id, String name) {

            HttpHeaders headers =createHeader();
            String requestJson = "{\"name\":\"" + name + "\"}";
            HttpEntity<String> request = new HttpEntity<String>(requestJson, headers);
            // external call time
            long startTime = System.currentTimeMillis();
            ResponseEntity<String> response = customRestTemplate().exchange(externalUrl, HttpMethod.POST, request,   
                    String.class);
            long endTime = System.currentTimeMillis();
            long duration = (endTime - startTime); // divide by 1000000 to get milliseconds.
            log.info("{\"RestTemplateDemo\":{\"id\":\"" + id + "\",\"external call duration\":" + duration + "}}");
            ObjectMapper mapper = new ObjectMapper();
            return response.getBody();
        }

The below code shows how you need to create the template for simple cases.

RestTemplate tmpl = new RestTemplateBuilder().setConnectTimeout(Duration.ofMillis(200))
                                             .setReadTimeout(Duration.ofMillis(100))
                                             .requestFactory(org.springframework.http.client.SimpleClientHttpRequestFactory.class)
                                             .build();

It would be better for you to provide the source code of MyHttpComponentFactoryBuilder class. But my suggestion is that to create a class MyHttpComponentFactory which extends SimpleClientHttpRequestFactory class migrate your codes from MyHttpComponentFactoryBuilder to it.