1. Overview

This tutorial will illustrate how to configure Basic Authentication on the Apache HttpClient 5. 

If you want to dig deeper and learn other cool things you can do with the HttpClient – head on over to the main HttpClient tutorial.

2. Basic Authentication With the API

Let’s start with the standard way of configuring Basic Authentication on the HttpClient – via a CredentialsProvider:

final HttpHost targetHost = new HttpHost("http", "localhost", 8082);
final BasicCredentialsProvider provider = new BasicCredentialsProvider();
AuthScope authScope = new AuthScope(targetHost);
provider.setCredentials(authScope, new UsernamePasswordCredentials(DEFAULT_USER, DEFAULT_PASS_ARRAY));

final HttpGet request = new HttpGet(URL_SECURED_BY_BASIC_AUTHENTICATION);

try (CloseableHttpClient client = HttpClientBuilder.create()
 .setDefaultCredentialsProvider(provider())
 .build();

 CloseableHttpResponse response = (CloseableHttpResponse) client
 .execute(request, new CustomHttpClientResponseHandler())) {
 final int statusCode = response.getCode();
 assertThat(statusCode, equalTo(HttpStatus.SC_OK));
}

As we can see, creating the client with a credentials provider to set it up with Basic Authentication is not difficult.

Now, to understand what HttpClient will actually do behind the scenes, we’ll need to look at the logs:

# ... request is sent with no credentials
[main] DEBUG ... - Authentication required
[main] DEBUG ... - localhost:8080 requested authentication
[main] DEBUG ... - Authentication schemes in the order of preference: 
 [negotiate, Kerberos, NTLM, Digest, Basic]
[main] DEBUG ... - Challenge for negotiate authentication scheme not available
[main] DEBUG ... - Challenge for Kerberos authentication scheme not available
[main] DEBUG ... - Challenge for NTLM authentication scheme not available
[main] DEBUG ... - Challenge for Digest authentication scheme not available
[main] DEBUG ... - Selected authentication options: [BASIC]
# ... the request is sent again - with credentials

The entire Client-Server communication is now clear:

• the Client sends the HTTP Request with no credentials
• the Server sends back a challenge
• the Client negotiates and identifies the right authentication scheme
• the Client sends a second Request, this time with credentials

3. Preemptive Basic Authentication

Out of the box, the HttpClient doesn’t do preemptive authentication. Instead, this has to be an explicit decision made by the client.

First, we need to create the HttpContext – pre-populating it with an authentication cache with the right type of authentication scheme pre-selected. This will mean that the negotiation from the previous example is no longer necessary – Basic Authentication is already chosen:

final HttpHost targetHost = new HttpHost("http", "localhost", 8082);
final BasicCredentialsProvider credsProvider = new BasicCredentialsProvider();
AuthScope authScope = new AuthScope(targetHost);
credsProvider.setCredentials(authScope, new UsernamePasswordCredentials(DEFAULT_USER, DEFAULT_PASS_ARRAY));

// Create AuthCache instance
final AuthCache authCache = new BasicAuthCache();
// Generate BASIC scheme object and add it to the local auth cache
authCache.put(targetHost, new BasicScheme());

// Add AuthCache to the execution context
final HttpClientContext context = HttpClientContext.create();
context.setCredentialsProvider(credsProvider);
context.setAuthCache(authCache);

Now we can use the client with the new context and send the pre-authentication request:

final HttpGet request = new HttpGet(URL_SECURED_BY_BASIC_AUTHENTICATION);
try (CloseableHttpClient client = HttpClientBuilder.create()
 .build();

 CloseableHttpResponse response = (CloseableHttpResponse) client
 .execute(request, context(), new CustomHttpClientResponseHandler())) {
 final int statusCode = response.getCode();
 assertThat(statusCode, equalTo(200));
}

Let’s look at the logs:

[main] DEBUG ... - Re-using cached 'basic' auth scheme for http://localhost:8082
[main] DEBUG ... - Executing request GET /spring-security-rest-basic-auth/api/foos/1 HTTP/1.1
[main] DEBUG ... >> GET /spring-security-rest-basic-auth/api/foos/1 HTTP/1.1
[main] DEBUG ... >> Host: localhost:8082
[main] DEBUG ... >> Authorization: Basic dXNlcjE6dXNlcjFQYXNz
[main] DEBUG ... << HTTP/1.1 200 OK
[main] DEBUG ... - Authentication succeeded

Everything looks OK:

• the “Basic Authentication” scheme is pre-selected
• the Request is sent with the Authorization header
• the Server responds with a 200 OK
• Authentication succeeds

4. Basic Auth With Raw HTTP Headers

Preemptive Basic Authentication basically means pre-sending the Authorization header.

So, instead of going through the rather complex previous example to set it up, we can take control of this header and construct it by hand:

final HttpGet request = new HttpGet(URL_SECURED_BY_BASIC_AUTHENTICATION);
final String auth = DEFAULT_USER + ":" + DEFAULT_PASS;
final byte[] encodedAuth = Base64.encodeBase64(auth.getBytes(StandardCharsets.ISO_8859_1));
final String authHeader = "Basic " + new String(encodedAuth);
request.setHeader(HttpHeaders.AUTHORIZATION, authHeader);

try (CloseableHttpClient client = HttpClientBuilder.create()
 .build();

 CloseableHttpResponse response = (CloseableHttpResponse) client
 .execute(request, new CustomHttpClientResponseHandler())) {
 final int statusCode = response.getCode();
 assertThat(statusCode, equalTo(HttpStatus.SC_OK));
}

Let’s make sure this is working correctly:

[main] DEBUG ... - Auth cache not set in the context
[main] DEBUG ... - Opening connection {}->http://localhost:8080
[main] DEBUG ... - Connecting to localhost/127.0.0.1:8080
[main] DEBUG ... - Executing request GET /spring-security-rest-basic-auth/api/foos/1 HTTP/1.1
[main] DEBUG ... - Proxy auth state: UNCHALLENGED
[main] DEBUG ... - http-outgoing-0 >> GET /spring-security-rest-basic-auth/api/foos/1 HTTP/1.1
[main] DEBUG ... - http-outgoing-0 >> Authorization: Basic dXNlcjE6dXNlcjFQYXNz
[main] DEBUG ... - http-outgoing-0 << HTTP/1.1 200 OK

So, even though there is no auth cache, Basic Authentication still works correctly and we receive 200 OK.

5. Conclusion

This article illustrated various ways to set up and use basic authentication with the Apache HttpClient.