您可以使用自定义resttemplate，示例如下：
yourcustomresttemplate.java：

class YourCustomRestTemplate implements RestTemplateCustomizer {

    @Override
    public void customize(RestTemplate restTemplate) {
        HttpHost proxy = new HttpHost(PROXY_SERVER_HOST, PROXY_SERVER_PORT);
        HttpClient httpClient = HttpClientBuilder.create()
            .setRoutePlanner(new DefaultProxyRoutePlanner(proxy) {
                @Override
                public HttpHost determineProxy(HttpHost target, HttpRequest request, HttpContext context) throws HttpException {
                    return super.determineProxy(target, request, context);
                }
            })
            .build();
        restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory(httpClient));
    }
}

当您要构建resttemplate对象以调用api时：

RestTemplate restTemplate = new RestTemplateBuilder(new YourCustomRestTemplate()).build();

ResponseEntity<String> responseEntity = restTemplate.getForEntity("__URL__/get", String.class);