本文将从代码的角度去引导如何使用httpclient的各个功能和特性。
import org.apache.commons.httpclient.*; import org.apache.commons.httpclient.methods.*; import org.apache.commons.httpclient.params.HttpMethodParams; import java.io.*; public class HttpClientTutorial { private static String url = "http://www.apache.org/"; public static void main(String[] args) { // Create an instance of HttpClient. HttpClient client = new HttpClient(); // Create a method instance. GetMethod method = new GetMethod(url); // Provide custom retry handler is necessary method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, false)); try { // Execute the method. int statusCode = client.executeMethod(method); if (statusCode != HttpStatus.SC_OK) { System.err.println("Method failed: " + method.getStatusLine()); } // Read the response body. byte[] responseBody = method.getResponseBody(); // Deal with the response. // Use caution: ensure correct character encoding and is not binary data System.out.println(new String(responseBody)); } catch (HttpException e) { System.err.println("Fatal protocol violation: " + e.getMessage()); e.printStackTrace(); } catch (IOException e) { System.err.println("Fatal transport error: " + e.getMessage()); e.printStackTrace(); } finally { // Release the connection. method.releaseConnection(); } } }
package org.apache.http.examples.client; import java.net.URI; import java.util.List; import org.apache.http.HttpEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.client.methods.RequestBuilder; import org.apache.http.cookie.Cookie; import org.apache.http.impl.client.BasicCookieStore; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.util.EntityUtils; /** * A example that demonstrates how HttpClient APIs can be used to perform * form-based logon. */ public class ClientFormLogin { public static void main(String[] args) throws Exception { BasicCookieStore cookieStore = new BasicCookieStore(); CloseableHttpClient httpclient = HttpClients.custom() .setDefaultCookieStore(cookieStore) .build(); try { HttpGet httpget = new HttpGet("https://someportal/"); CloseableHttpResponse response1 = httpclient.execute(httpget); try { HttpEntity entity = response1.getEntity(); System.out.println("Login form get: " + response1.getStatusLine()); EntityUtils.consume(entity); System.out.println("Initial set of cookies:"); List<Cookie> cookies = cookieStore.getCookies(); if (cookies.isEmpty()) { System.out.println("None"); } else { for (int i = 0; i < cookies.size(); i++) { System.out.println("- " + cookies.get(i).toString()); } } } finally { response1.close(); } HttpUriRequest login = RequestBuilder.post() .setUri(new URI("https://someportal/")) .addParameter("IDToken1", "username") .addParameter("IDToken2", "password") .build(); CloseableHttpResponse response2 = httpclient.execute(login); try { HttpEntity entity = response2.getEntity(); System.out.println("Login form get: " + response2.getStatusLine()); EntityUtils.consume(entity); System.out.println("Post logon cookies:"); List<Cookie> cookies = cookieStore.getCookies(); if (cookies.isEmpty()) { System.out.println("None"); } else { for (int i = 0; i < cookies.size(); i++) { System.out.println("- " + cookies.get(i).toString()); } } } finally { response2.close(); } } finally { httpclient.close(); } } }
/** * Example how to use multipart/form encoded POST request. */ public class ClientMultipartFormPost { public static void main(String[] args) throws Exception { if (args.length != 1) { System.out.println("File path not given"); System.exit(1); } CloseableHttpClient httpclient = HttpClients.createDefault(); try { HttpPost httppost = new HttpPost("http://localhost:8080" + "/servlets-examples/servlet/RequestInfoExample"); FileBody bin = new FileBody(new File(args[0])); StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN); HttpEntity reqEntity = MultipartEntityBuilder.create() .addPart("bin", bin) .addPart("comment", comment) .build(); httppost.setEntity(reqEntity); System.out.println("executing request " + httppost.getRequestLine()); CloseableHttpResponse response = httpclient.execute(httppost); try { System.out.println("----------------------------------------"); System.out.println(response.getStatusLine()); HttpEntity resEntity = response.getEntity(); if (resEntity != null) { System.out.println("Response content length: " + resEntity.getContentLength()); } EntityUtils.consume(resEntity); } finally { response.close(); } } finally { httpclient.close(); } } }
/** * This example demonstrates the use of the {@link ResponseHandler} to simplify * the process of processing the HTTP response and releasing associated resources. */ public class ClientWithResponseHandler { public final static void main(String[] args) throws Exception { CloseableHttpClient httpclient = HttpClients.createDefault(); try { HttpGet httpget = new HttpGet("http://localhost/"); System.out.println("Executing request " + httpget.getRequestLine()); // Create a custom response handler ResponseHandler<String> responseHandler = new ResponseHandler<String>() { public String handleResponse( final HttpResponse response) throws ClientProtocolException, IOException { int status = response.getStatusLine().getStatusCode(); if (status >= 200 && status < 300) { HttpEntity entity = response.getEntity(); return entity != null ? EntityUtils.toString(entity) : null; } else { throw new ClientProtocolException("Unexpected response status: " + status); } } }; String responseBody = httpclient.execute(httpget, responseHandler); System.out.println("----------------------------------------"); System.out.println(responseBody); } finally { httpclient.close(); } } }
/** * An example that performs GETs from multiple threads. * */ public class ClientMultiThreadedExecution { public static void main(String[] args) throws Exception { // Create an HttpClient with the ThreadSafeClientConnManager. // This connection manager must be used if more than one thread will // be using the HttpClient. PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(); cm.setMaxTotal(100); CloseableHttpClient httpclient = HttpClients.custom() .setConnectionManager(cm) .build(); try { // create an array of URIs to perform GETs on String[] urisToGet = { "http://hc.apache.org/", "http://hc.apache.org/httpcomponents-core-ga/", "http://hc.apache.org/httpcomponents-client-ga/", }; // create a thread for each URI GetThread[] threads = new GetThread[urisToGet.length]; for (int i = 0; i < threads.length; i++) { HttpGet httpget = new HttpGet(urisToGet[i]); threads[i] = new GetThread(httpclient, httpget, i + 1); } // start the threads for (int j = 0; j < threads.length; j++) { threads[j].start(); } // join the threads for (int j = 0; j < threads.length; j++) { threads[j].join(); } } finally { httpclient.close(); } } /** * A thread that performs a GET. */ static class GetThread extends Thread { private final CloseableHttpClient httpClient; private final HttpContext context; private final HttpGet httpget; private final int id; public GetThread(CloseableHttpClient httpClient, HttpGet httpget, int id) { this.httpClient = httpClient; this.context = new BasicHttpContext(); this.httpget = httpget; this.id = id; } /** * Executes the GetMethod and prints some status information. */ @Override public void run() { try { System.out.println(id + " - about to get something from " + httpget.getURI()); CloseableHttpResponse response = httpClient.execute(httpget, context); try { System.out.println(id + " - get executed"); // get the response body as an array of bytes HttpEntity entity = response.getEntity(); if (entity != null) { byte[] bytes = EntityUtils.toByteArray(entity); System.out.println(id + " - " + bytes.length + " bytes read"); } } finally { response.close(); } } catch (Exception e) { System.out.println(id + " - error: " + e); } } } }