As described in Section 33.1, “RestTemplate customization”, a RestTemplateCustomizer can be used with RestTemplateBuilder to build a customized RestTemplate. This is the recommended approach for creating a RestTemplate configured to use a proxy.

The exact details of the proxy configuration depend on the underlying client request factory that is being used. Here’s an example of configuring HttpComponentsClientRequestFactory with an HttpClient that uses a proxy for all hosts except 192.168.0.5.

static class ProxyCustomizer implements RestTemplateCustomizer {

	@Override
	public void customize(RestTemplate restTemplate) {
		HttpHost proxy = new HttpHost("proxy.example.com");
		HttpClient httpClient = HttpClientBuilder.create()
				.setRoutePlanner(new DefaultProxyRoutePlanner(proxy) {

					@Override
					public HttpHost determineProxy(HttpHost target,
							HttpRequest request, HttpContext context)
									throws HttpException {
						if (target.getHostName().equals("192.168.0.5")) {
							return null;
						}
						return super.determineProxy(target, request, context);
					}

				}).build();
		restTemplate.setRequestFactory(
				new HttpComponentsClientHttpRequestFactory(httpClient));
	}

}