Java: Authenticate via HttpClient 4

It's often might be needed to get/post some info from the third party sites via HTTP. But, most of the times you have to be signed into that web-resources. ## Authentication ### Authenticate via POST with parameters: <pre><code class="language-java"> public String authenticate() throws IOException, AuthenticationException { HttpPost httpPost = new HttpPost(signInUrl); ArrayList<NameValuePair> params = new ArrayList<>(2); params.add(new BasicNameValuePair("username", authUser)); params.add(new BasicNameValuePair("password", authPassword)); httpPost.setEntity(new UrlEncodedFormEntity(params)); logger.info("Executing Authentication Request: " + httpPost.getRequestLine()); CloseableHttpResponse response = httpClient.execute(httpPost); logger.info("HTML5 Authentication Response: " + response.getStatusLine()); int statusCode = response.getStatusLine().getStatusCode(); if (!HttpStatus.valueOf(statusCode).is2xxSuccessful()) { throw new RuntimeException("Error making an Authentication request | statusCode = " + statusCode); } return EntityUtils.toString(response.getEntity()); } </code></pre> > It's nice to do it in lazy way: > Whenever you do any GET/POST request, check if it's failed with 401 satusCode *(UNAUTHORIZED)*, > then authenticate and re-send previously failed request. ### Make requests with pre-Authorization: <pre><code class="language-java"> BasicCredentialsProvider provider = new BasicCredentialsProvider(); provider.setCredentials(new AuthScope(AuthScope.ANY_HOST, AuthScope.ANY_PORT), new UsernamePasswordCredentials(authUser, authToken)); httpClient = HttpClientBuilder.create() .setDefaultCredentialsProvider(provider).build(); public String makeRequest(URI uri, HttpRequestBase request) throws IOException { HttpHost host = new HttpHost(uri.getHost(), uri.getPort(), uri.getScheme()); // Create AuthCache instance AuthCache authCache = new BasicAuthCache(); // Generate BASIC scheme object and add it to the local auth cache BasicScheme basicAuth = new BasicScheme(); authCache.put(host, basicAuth); // Add AuthCache to the execution context HttpClientContext localContext = HttpClientContext.create(); localContext.setAuthCache(authCache); logger.info("Executing Request: " + request.getRequestLine()); CloseableHttpResponse response = httpClient.execute( host, request, localContext ); int statusCode = response.getStatusLine().getStatusCode(); if (!HttpStatus.valueOf(statusCode).is2xxSuccessful()) { throw new RuntimeException("Error making Request | statusCode = " + statusCode); } return EntityUtils.toString(response.getEntity()); } </code></pre> ---- ## see Also * [Post with HttpClient](http://www.baeldung.com/httpclient-post-http-request) * [All Http Status Codes](http://www.restapitutorial.com/httpstatuscodes.html) * [Spring 4 API - HttpStatus](https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpStatus.html) * [Java EE 7 API - Response.Status](http://docs.oracle.com/javaee/7/api/javax/ws/rs/core/Response.Status.html) * [Apache Commons - HttpStatus](https://hc.apache.org/httpcomponents-core-ga/httpcore/apidocs/org/apache/http/HttpStatus.html) * [REST (Restful Web Services) ](http://bloomlab.blogspot.com.ee/2015/07/rest-restfull-webservices.html) * [Themeleaf - Offsite](http://www.thymeleaf.org/) * [Web Resource Optimizer for Java](http://alexo.github.io/wro4j/) * [Wro4j - Github](https://github.com/wro4j/wro4j) * [Keynote: Top JS frmeworks 2015](http://bloomlab.blogspot.com.ee/2015/03/top-javascript-frameworks-2015.html)