Spring Allow repeatable writes in StreamingHttpOutputMessage

`BufferingClientHttpRequestFactory` creates requests which are not repeatable

A RestTemplate obtained form the following snippet will lose the default request configuration applied to the HttpComponentsClientHttpRequestFactory, in this case the setRedirectsEnabled(true) is not honored.

Affected Version: spring-boot 3.2.0-M3
Works with stable: spring-boot 3.1.4
Affected http client library is Apache HttpComponents 5 (HttpComponentsClientHttpRequestFactory).

I prepared a reproducible example here. Just run com.example.httpclient5demo.Httpclient5DemoApplicationTests

        RestTemplate restTemplate = restTemplateBuilder
                .requestFactory(() -> {
                    RequestConfig.Builder requestConfig = RequestConfig.custom()
                            .setRedirectsEnabled(true);
                    HttpClientBuilder httpClientBuilder = HttpClientBuilder.create()
                            .setDefaultRequestConfig(requestConfig.build());
                    HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClientBuilder.build());
                    //return requestFactory;
                    return new BufferingClientHttpRequestFactory(requestFactory);
                })
                .rootUri("https://httpbin.org")
                .build();
        String response = restTemplate.getForObject("/redirect-to?url=https://httpbin.org/base64/SFRUUEJJTiBpcyBhd2Vzb21l", String.class);
        assertThat(response).isEqualTo("HTTPBIN is awesome");

Comment From: wilkinsona

Thanks for the report and sample project. This doesn't appear to be a Spring Boot problem. The following tests illustrate the behavior without using Spring Boot:

package com.example.httpclient5demo;

import static org.assertj.core.api.Assertions.assertThat;

import org.apache.hc.client5.http.config.RequestConfig;
import org.apache.hc.client5.http.impl.classic.HttpClientBuilder;
import org.junit.jupiter.api.Test;
import org.springframework.http.client.BufferingClientHttpRequestFactory;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

class Httpclient5DemoApplicationTests {

    @Test
    void redirectsCanBeEnabled() {
        RestTemplate restTemplate = new RestTemplate();
        RequestConfig.Builder requestConfig = RequestConfig.custom()
                .setRedirectsEnabled(true);
        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create()
                .setDefaultRequestConfig(requestConfig.build());
        HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClientBuilder.build());
        restTemplate.setRequestFactory(requestFactory);
        String response = restTemplate.getForObject("https://httpbin.org/redirect-to?url=https://httpbin.org/base64/SFRUUEJJTiBpcyBhd2Vzb21l", String.class);
        assertThat(response).isEqualTo("HTTPBIN is awesome");
    }

    @Test
    void redirectsCanBeEnabledWhenBuffering() {
        RestTemplate restTemplate = new RestTemplate();
        RequestConfig.Builder requestConfig = RequestConfig.custom()
                .setRedirectsEnabled(true);
        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create()
                .setDefaultRequestConfig(requestConfig.build());
        HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClientBuilder.build());
        restTemplate.setRequestFactory(new BufferingClientHttpRequestFactory(requestFactory));
        String response = restTemplate.getForObject("https://httpbin.org/redirect-to?url=https://httpbin.org/base64/SFRUUEJJTiBpcyBhd2Vzb21l", String.class);
        assertThat(response).isEqualTo("HTTPBIN is awesome");
    }

}

redirectsCanBeEnabled passes but redirectsCanBeEnabledWhenBuffering fails. We'll transfer this to the Framework team so that they can take a look.