Add Custom ClientHttpRequestInterceptor in RestTemplateBuilder with HttpComponentsClientHttpRequestFactory

Question

I need to add a Custom Header in all my RestTemplate Client requests. So I implemented ClientHttpRequestInterceptor. And I add the interceptor in my RestTemplateBuilder config like shown below. The problem is that when the RestTemplate makes the HTTP call it throws following exception:

java.lang.ClassCastException: org.springframework.http.client.InterceptingClientHttpRequestFactory cannot be cast to org.springframework.http.client.HttpComponentsClientHttpRequestFactory

RestTemplate Bean Creation :

@Bean
  public RestTemplate restTemplate(RestTemplateBuilder restTemplateBuilder) {
    PoolingHttpClientConnectionManager poolingConnectionManager = new PoolingHttpClientConnectionManager();
    poolingConnectionManager.setMaxTotal(restTemplateProps.getMaxConnectionsPerPool());
    poolingConnectionManager.setDefaultMaxPerRoute(restTemplateProps.getMaxDefaultConnectionPerRoute());
    CloseableHttpClient client = HttpClientBuilder.create().setConnectionManager(poolingConnectionManager).build();
    ClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(client);
    restTemplateBuilder = restTemplateBuilder.additionalInterceptors(new MyClientHttpRequestInterceptor());
    return restTemplateBuilder.requestFactory(clientHttpRequestFactory).build();
  }

Also, I am updating the timeouts later in below code:

  protected void setRestTemplateTimeouts() {

    HttpComponentsClientHttpRequestFactory rf =
        (HttpComponentsClientHttpRequestFactory) restTemplate.getRequestFactory();
    rf.setConnectTimeout(restTemplateProps.getConnectionTimeout());
    rf.setReadTimeout(restTemplateProps.getSocketTimeout());
  }

Can anyone help me fix this?

Answer 1

The problem was, I was trying to set the connect and read timeouts after setting the ClientHttpRequestInterceptor.

In my setRestTemplateTimeouts() method when I try to fetch & typecast requestFactory to HttpComponentsClientHttpRequestFactory, I get the ClassCastException exception because restTemplate.getRequestFactory() returns InterceptingClientHttpRequestFactory instead of HttpComponentsClientHttpRequestFactory. This is because I added an interceptor in my restTemplate object.

Solution is to set the timeouts before setting interceptor because you can't set timeouts after setting an interceptor. Refer the code below:

@Bean
  public RestTemplate restTemplate(RestTemplateBuilder restTemplateBuilder) {
    PoolingHttpClientConnectionManager poolingConnectionManager = new PoolingHttpClientConnectionManager();
    poolingConnectionManager.setMaxTotal(restTemplateProps.getMaxConnectionsPerPool());
    poolingConnectionManager.setDefaultMaxPerRoute(restTemplateProps.getMaxDefaultConnectionPerRoute());
    CloseableHttpClient client = HttpClientBuilder.create().setConnectionManager(poolingConnectionManager).build();
    HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(client);
    clientHttpRequestFactory.setConnectTimeout(restTemplateProps.getConnectionTimeout());
    clientHttpRequestFactory.setReadTimeout(restTemplateProps.getSocketTimeout());
    restTemplateBuilder = restTemplateBuilder.additionalInterceptors(new MyClientHttpRequestInterceptor());
    return restTemplateBuilder.requestFactory(clientHttpRequestFactory).build();
  }