SpringBoot RestTemplateBuilder.setConnectTimeout not working when using RestTemplateCustomizer to customize RequestFactory

Spring Boot Version: 2.1.18.RELEASE, 2.3.12.RELEASE, 2.5.2

I use okhttpas the RequestFactory of RestTemplate, so i create a RestTemplateCustomizer bean.

@Bean
public RestTemplateCustomizer okHttpRequestFactoryRestTemplateCustomizer() {
    return restTemplate ->
            restTemplate.setRequestFactory(new OkHttp3ClientHttpRequestFactory(new OkHttpClient.Builder().build()));
}

@Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
    return builder
            .setConnectTimeout(Duration.ofSeconds(3))
            .build();
}

But the setConnectTimeout not working, i debugged the build process, i found that setting the timeout period is in the buildRequestFactory() phase, while the custom setting RequestFactory is executed at the end, so it did not work.

public <T extends RestTemplate> T configure(T restTemplate) {
    ClientHttpRequestFactory requestFactory = buildRequestFactory();
    // ...
    if (!CollectionUtils.isEmpty(this.customizers)) {
        for (RestTemplateCustomizer customizer : this.customizers) {
            customizer.customize(restTemplate);
        }
    }
    return restTemplate;
}

Comment From: wilkinsona

This is to be expected. As the builder’s javadoc notes, the builder configures the connect timeout on the underlying request factory and customizers are applied after the builder configuration has been applied. You are replacing the request factory in a customizer so you have overridden the builder’s configuration.

Rather than using a RestTemplateCustomizer to change the request factory, I would recommend defining your own RestTemplateBuilder bean with a customized request factory instead.