Preemptive Basic authentication with Apache HttpClient 4

I don't quite get your closing comment. It's the HttpClient that has all of that machinery for doing preemptive auth, and you only have to do that once (when you construct and configure your HttpClient). Once you've done that, you construct your method instances the same way as always. You don't "add the BasicHttpContext" to the method.

Your best bet, I'd think, is to have your own object that sets up all of the junk required for preemptive auth, and has a simple method or methods for executing requests on given HTTPMethod objects.

SolrConfig:

@Configuration
public class SolrConfig {

    @Value("${solr.http.url}")
    private String solrUrl;

    @Value("${solr.http.username}")
    private String solrUser;

    @Value("${solr.http.password}")
    private String solrPassword;

    @Value("${solr.http.pool.maxTotal}")
    private int poolMaxTotal;

    @Value("${solr.http.pool.maxPerRoute}")
    private int pollMaxPerRoute;

    @Bean
    public SolrClient solrClient() {
        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
        connectionManager.setMaxTotal(poolMaxTotal);
        connectionManager.setDefaultMaxPerRoute(pollMaxPerRoute);

        CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(solrUser, solrPassword));

        CloseableHttpClient httpClient = HttpClientBuilder.create()
                .addInterceptorFirst(new PreemptiveAuthInterceptor())
                .setConnectionManager(connectionManager)
                .setDefaultCredentialsProvider(credentialsProvider)
                .build();

        return new HttpSolrClient.Builder(solrUrl).withHttpClient(httpClient).build();
    }


}

PreemptiveAuthInterceptor:

public class PreemptiveAuthInterceptor implements HttpRequestInterceptor {

    public void process(final HttpRequest request, final HttpContext context)
            throws HttpException {
        AuthState authState = (AuthState) context
                .getAttribute(HttpClientContext.TARGET_AUTH_STATE);

        // If no auth scheme available yet, try to initialize it
        // preemptively
        if (authState.getAuthScheme() == null) {
            CredentialsProvider credentialsProvider = (CredentialsProvider) context
                    .getAttribute(HttpClientContext.CREDS_PROVIDER);
            HttpHost targetHost = (HttpHost) context
                    .getAttribute(HttpCoreContext.HTTP_TARGET_HOST);
            Credentials credentials = credentialsProvider.getCredentials(new AuthScope(
                    targetHost.getHostName(), targetHost.getPort()));
            if (credentials == null) {
                throw new HttpException(
                        "No credentials for preemptive authentication");
            }
            authState.update(new BasicScheme(), credentials);
        }

    }

}