HttpClient
一 简介
1.尽管java.net包提供了基本通过HTTP访问资源的功能，但它没有提供全面的灵活性和其它很多应用程序需要的功能。HttpClient就是寻求弥补这项空白的组件，通过提供一个有效的，保持更新的，功能丰富的软件包来实现客户端最新的HTTP标准和建议。
为扩展而设计，同时为基本的HTTP协议提供强大的支持，HttpClient组件也许就是构建HTTP客户端应用程序，比如web浏览器，web服务端，利用或扩展HTTP协议进行分布式通信的系统的开发人员的关注点。
2.HttpClient不是一个浏览器。它是一个客户端的HTTP通信实现库。HttpClient的目标是发送和接收HTTP报文。HttpClient不会去缓存内容，执行嵌入在HTML页面中的javascript代码，猜测内容类型，重新格式化请求/重定向URI，或者其它和HTTP运输无关的功能。
二 使用
1.执行请求
(1)HttpClient最重要的功能是执行HTTP方法。一个HTTP方法的执行包含一个或多个HTTP请求/HTTP响应交换，通常由HttpClient的内部来处理。而期望用户提供一个要执行的请求对象，而HttpClient期望传输请求到目标服务器并返回对应的响应对象，或者当执行不成功时抛出异常。
一个很简单的请求执行过程的示例：
HttpClient httpclient = new DefaultHttpClient();HttpGet httpget = new HttpGet("http://localhost/");HttpResponse response = httpclient.execute(httpget);HttpEntity entity = response.getEntity();if (entity != null) {InputStream instream = entity.getContent();int l;byte[] tmp = new byte[2048];while ((l = instream.read(tmp)) != -1) {}}(2)HTTP请求
所有HTTP请求有一个组合了方法名，请求URI和HTTP协议版本的请求行。
HttpClient支持所有定义在HTTP/1.1版本中的HTTP方法：GET，HEAD，POST，PUT，DELETE，TRACE和OPTIONS。对于每个方法类型都有一个特殊的类：HttpGet，HttpHead，HttpPost，HttpPut，HttpDelete，HttpTrace和HttpOptions。
请求的URI是统一资源定位符，它标识了应用于哪个请求之上的资源。HTTP请求URI包含一个协议模式，主机名称，可选的端口，资源路径，可选的查询和可选的片段。
HttpClient提供很多工具方法来简化创建和修改执行URI。
a.使用URIUtils工具类
URI uri = URIUtils.createURI("http", "www.google.com", -1, "/search","q=httpclient&btnG=Google+Search&aq=f&oq=", null);HttpGet httpget = new HttpGet(uri);System.out.println(httpget.getURI());结果：http://www.google.com/search?q=httpclient&btnG=Google+Search&aq=f&oq=
b.查询字符串也可以从独立的参数中来生成
List<NameValuePair> qparams = new ArrayList<NameValuePair>();qparams.add(new BasicNameValuePair("q", "httpclient"));qparams.add(new BasicNameValuePair("btnG", "Google Search"));qparams.add(new BasicNameValuePair("aq", "f"));qparams.add(new BasicNameValuePair("oq", null));URI uri = URIUtils.createURI("http", "www.google.com", -1, "/search",URLEncodedUtils.format(qparams, "UTF-8"), null);HttpGet httpget = new HttpGet(uri);System.out.println(httpget.getURI());结果：http://www.google.com/search?q=httpclient&btnG=Google+Search&aq=f&oq=
(3)HTTP响应
HTTP响应是由服务器在接收和解释请求报文之后返回发送给客户端的报文。响应报文的第一行包含了协议版本，之后是数字状态码和相关联的文本段。
HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1,HttpStatus.SC_OK, "OK");System.out.println(response.getProtocolVersion());System.out.println(response.getStatusLine().getStatusCode());System.out.println(response.getStatusLine().getReasonPhrase());System.out.println(response.getStatusLine().toString());
结果：
HTTP/1.1
200
OK
HTTP/1.1 200 OK
(4)处理报文头部
一个HTTP报文可以包含很多描述如内容长度，内容类型等信息属性的头部信息。
HttpClient提供获取，添加，移除和枚举头部信息的方法。
HttpResponse response = new BasicHttpResponse(HttpVersion.HTTP_1_1,HttpStatus.SC_OK, "OK");response.addHeader("Set-Cookie","c1=a; path=/; domain=localhost");response.addHeader("Set-Cookie","c2=b; path=\"/\", c3=c; domain=\"localhost\"");Header h1 = response.getFirstHeader("Set-Cookie");System.out.println(h1);Header h2 = response.getLastHeader("Set-Cookie");System.out.println(h2);Header[] hs = response.getHeaders("Set-Cookie");System.out.println(hs.length);结果：
Set-Cookie: c1=a; path=/; domain=localhost
Set-Cookie: c2=b; path="/", c3=c; domain="localhost"
三 使用HttpClient发送请求、接收响应
1.一般需要如下几步:
(1) 创建HttpClient对象。
(2)创建请求方法的实例，并指定请求URL。如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。
(3) 如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数。
(4) 调用HttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个HttpResponse。
(5) 调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。
(6) 释放连接。无论执行方法是否成功，都必须释放连接
2.使用httpClient的两种方式：
(1)第一种：
public class HttpClientExample { ???public static void main(String args[]) throws IOException{ ???????List<NameValuePair> formparams=new ArrayList<NameValuePair>(); ???????formparams.add(new BasicNameValuePair("account","")); ???????formparams.add(new BasicNameValuePair("password","")); ???????HttpEntity reqEntity=new UrlEncodedFormEntity(formparams,"utf-8"); ???????RequestConfig requestConfig = RequestConfig.custom() ???????????????.setSocketTimeout(5000) ???????????????.setConnectTimeout(5000) ???????????????.setConnectionRequestTimeout(5000) ???????????????.build(); ???????HttpClient client = new DefaultHttpClient(); ???????HttpPost post = new HttpPost("http://baidu.com"); ???????post.setEntity(reqEntity); ???????post.setConfig(requestConfig); ???????HttpResponse response = client.execute(post); ???????if (response.getStatusLine().getStatusCode() == 200) { ???????????HttpEntity resEntity = response.getEntity(); ???????????String message = EntityUtils.toString(resEntity, "utf-8"); ???????????System.out.println(message); ???????} else { ???????????System.out.println("请求失败"); ???????} ???}}(2)第二种：这种方式是用了一个http的连接池，同时使用httpbuilder构造合适的http方法
public class HttpClientExample2 { ???private static PoolingHttpClientConnectionManager connectionManager = null; ???private static HttpClientBuilder httpBulder = null; ???private static RequestConfig requestConfig = null; ???private static int MAXCONNECTION = 10; ???private static int DEFAULTMAXCONNECTION = 5; ???private static String IP = "cnivi.com.cn"; ???private static int PORT = 80; ???static { ???????//设置http的状态参数 ???????requestConfig = RequestConfig.custom() ???????????????.setSocketTimeout(5000) ???????????????.setConnectTimeout(5000) ???????????????.setConnectionRequestTimeout(5000) ???????????????.build(); ???????HttpHost target = new HttpHost(IP, PORT); ???????connectionManager = new PoolingHttpClientConnectionManager(); ???????connectionManager.setMaxTotal(MAXCONNECTION); ???????connectionManager.setDefaultMaxPerRoute(DEFAULTMAXCONNECTION); ???????connectionManager.setMaxPerRoute(new HttpRoute(target), 20); ???????httpBulder = HttpClients.custom(); ???????httpBulder.setConnectionManager(connectionManager); ???} ???public static CloseableHttpClient getConnection() { ???????CloseableHttpClient httpClient = httpBulder.build(); ???????httpClient = httpBulder.build(); ???????return httpClient; ???} ???public static HttpUriRequest getRequestMethod(Map<String, String> map, String url, String method) { ???????List<NameValuePair> params = new ArrayList<NameValuePair>(); ???????Set<Map.Entry<String, String>> entrySet = map.entrySet(); ???????for (Map.Entry<String, String> e : entrySet) { ???????????String name = e.getKey(); ???????????String value = e.getValue(); ???????????NameValuePair pair = new BasicNameValuePair(name, value); ???????????params.add(pair); ???????} ???????HttpUriRequest reqMethod = null; ???????if ("post".equals(method)) { ???????????reqMethod = RequestBuilder.post().setUri(url) ???????????????????.addParameters(params.toArray(new BasicNameValuePair[params.size()])) ???????????????????.setConfig(requestConfig).build(); ???????} else if ("get".equals(method)) { ???????????reqMethod = RequestBuilder.get().setUri(url) ???????????????????.addParameters(params.toArray(new BasicNameValuePair[params.size()])) ???????????????????.setConfig(requestConfig).build(); ???????} ???????return reqMethod; ???} ???public static void main(String args[]) throws IOException { ???????Map<String, String> map = new HashMap<String, String>(); ???????map.put("account", ""); ???????map.put("password", ""); ???????HttpClient client = getConnection(); ???????HttpUriRequest post = getRequestMethod(map, "http://baidu.com", "post"); ???????HttpResponse response = client.execute(post); ???????if (response.getStatusLine().getStatusCode() == 200) { ???????????HttpEntity entity = response.getEntity(); ???????????String message = EntityUtils.toString(entity, "utf-8"); ???????????System.out.println(message); ???????} else { ???????????System.out.println("请求失败"); ???????} ???}}3.再看一个例子
import org.apache.http.HttpEntity;import org.apache.http.NameValuePair;import org.apache.http.client.ClientProtocolException;import org.apache.http.client.entity.UrlEncodedFormEntity;import org.apache.http.client.methods.CloseableHttpResponse;import org.apache.http.client.methods.HttpGet;import org.apache.http.client.methods.HttpPost;import org.apache.http.conn.ssl.SSLConnectionSocketFactory;import org.apache.http.conn.ssl.SSLContexts;import org.apache.http.conn.ssl.TrustSelfSignedStrategy;import org.apache.http.impl.client.CloseableHttpClient;import org.apache.http.impl.client.HttpClients;import org.apache.http.message.BasicNameValuePair;import org.apache.http.util.EntityUtils;import org.junit.Test;import javax.net.ssl.SSLContext;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.UnsupportedEncodingException;import java.security.KeyManagementException;import java.security.KeyStore;import java.security.KeyStoreException;import java.security.NoSuchAlgorithmException;import java.security.cert.CertificateException;import java.util.ArrayList;import java.util.List;public class HttpClientExample3{ ???@Test ???public void jUnitTest() { ???????get(); ???} ???/** ????* HttpClient连接SSL ????*/ ???public void ssl() { ???????CloseableHttpClient httpclient = null; ???????try { ???????????KeyStore trustStore = KeyStore.getInstance(KeyStore.getDefaultType()); ???????????FileInputStream instream = new FileInputStream(new File("d:\\tomcat.keystore")); ???????????try { ???????????????// 加载keyStore d:\\tomcat.keystore ???????????????trustStore.load(instream, "123456".toCharArray()); ???????????} catch (CertificateException e) { ???????????????e.printStackTrace(); ???????????} finally { ???????????????try { ???????????????????instream.close(); ???????????????} catch (Exception ignore) { ???????????????} ???????????} ???????????// 相信自己的CA和所有自签名的证书 ???????????SSLContext sslcontext = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build(); ???????????// 只允许使用TLSv1协议 ???????????SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(sslcontext, new String[] { "TLSv1" }, null, ???????????????????SSLConnectionSocketFactory.BROWSER_COMPATIBLE_HOSTNAME_VERIFIER); ???????????httpclient = HttpClients.custom().setSSLSocketFactory(sslsf).build(); ???????????// 创建http请求(get方式) ???????????HttpGet httpget = new HttpGet("https://localhost:8443/myDemo/Ajax/serivceJ.action"); ???????????System.out.println("executing request" + httpget.getRequestLine()); ???????????CloseableHttpResponse response = httpclient.execute(httpget); ???????????try { ???????????????HttpEntity entity = response.getEntity(); ???????????????System.out.println("----------------------------------------"); ???????????????System.out.println(response.getStatusLine()); ???????????????if (entity != null) { ???????????????????System.out.println("Response content length: " + entity.getContentLength()); ???????????????????System.out.println(EntityUtils.toString(entity)); ???????????????????EntityUtils.consume(entity); ???????????????} ???????????} finally { ???????????????response.close(); ???????????} ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} catch (KeyManagementException e) { ???????????e.printStackTrace(); ???????} catch (NoSuchAlgorithmException e) { ???????????e.printStackTrace(); ???????} catch (KeyStoreException e) { ???????????e.printStackTrace(); ???????} finally { ???????????if (httpclient != null) { ???????????????try { ???????????????????httpclient.close(); ???????????????} catch (IOException e) { ???????????????????e.printStackTrace(); ???????????????} ???????????} ???????} ???} ???/** ????* post方式提交表单（模拟用户登录请求） ????*/ ???public void postForm() { ???????// 创建默认的httpClient实例. ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????// 创建httppost ???????HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action"); ???????// 创建参数队列 ???????List<NameValuePair> formparams = new ArrayList<NameValuePair>(); ???????formparams.add(new BasicNameValuePair("username", "admin")); ???????formparams.add(new BasicNameValuePair("password", "123456")); ???????UrlEncodedFormEntity uefEntity; ???????try { ???????????uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); ???????????httppost.setEntity(uefEntity); ???????????System.out.println("executing request " + httppost.getURI()); ???????????CloseableHttpResponse response = httpclient.execute(httppost); ???????????try { ???????????????HttpEntity entity = response.getEntity(); ???????????????if (entity != null) { ???????????????????System.out.println("--------------------------------------"); ???????????????????System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8")); ???????????????????System.out.println("--------------------------------------"); ???????????????} ???????????} finally { ???????????????response.close(); ???????????} ???????} catch (ClientProtocolException e) { ???????????e.printStackTrace(); ???????} catch (UnsupportedEncodingException e1) { ???????????e1.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????// 关闭连接,释放资源 ???????????try { ???????????????httpclient.close(); ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???} ???/** ????* 发送 post请求访问本地应用并根据传递参数不同返回不同结果 ????*/ ???public void post() { ???????// 创建默认的httpClient实例. ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????// 创建httppost ???????HttpPost httppost = new HttpPost("http://localhost:8080/myDemo/Ajax/serivceJ.action"); ???????// 创建参数队列 ???????List<NameValuePair> formparams = new ArrayList<NameValuePair>(); ???????formparams.add(new BasicNameValuePair("type", "house")); ???????UrlEncodedFormEntity uefEntity; ???????try { ???????????uefEntity = new UrlEncodedFormEntity(formparams, "UTF-8"); ???????????httppost.setEntity(uefEntity); ???????????System.out.println("executing request " + httppost.getURI()); ???????????CloseableHttpResponse response = httpclient.execute(httppost); ???????????try { ???????????????HttpEntity entity = response.getEntity(); ???????????????if (entity != null) { ???????????????????System.out.println("--------------------------------------"); ???????????????????System.out.println("Response content: " + EntityUtils.toString(entity, "UTF-8")); ???????????????????System.out.println("--------------------------------------"); ???????????????} ???????????} finally { ???????????????response.close(); ???????????} ???????} catch (ClientProtocolException e) { ???????????e.printStackTrace(); ???????} catch (UnsupportedEncodingException e1) { ???????????e1.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????// 关闭连接,释放资源 ???????????try { ???????????????httpclient.close(); ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???} ???/** ????* 发送 get请求 ????*/ ???public void get() { ???????CloseableHttpClient httpclient = HttpClients.createDefault(); ???????try { ???????????// 创建httpget. ???????????HttpGet httpget = new HttpGet("http://www.baidu.com/"); ???????????System.out.println("executing request " + httpget.getURI()); ???????????// 执行get请求. ???????????CloseableHttpResponse response = httpclient.execute(httpget); ???????????try { ???????????????// 获取响应实体 ???????????????HttpEntity entity = response.getEntity(); ???????????????System.out.println("--------------------------------------"); ???????????????// 打印响应状态 ???????????????System.out.println(response.getStatusLine()); ???????????????if (entity != null) { ???????????????????// 打印响应内容长度 ???????????????????System.out.println("Response content length: " + entity.getContentLength()); ???????????????????// 打印响应内容 ???????????????????System.out.println("Response content: " + EntityUtils.toString(entity)); ???????????????} ???????????????System.out.println("------------------------------------"); ???????????} finally { ???????????????response.close(); ???????????} ???????} catch (ClientProtocolException e) { ???????????e.printStackTrace(); ???????} catch (IOException e) { ???????????e.printStackTrace(); ???????} finally { ???????????// 关闭连接,释放资源 ???????????try { ???????????????httpclient.close(); ???????????} catch (IOException e) { ???????????????e.printStackTrace(); ???????????} ???????} ???}}还可以参考一下这个：
public String ?getResponseXMLFromURL(String url){ ???????String result = null; ???????CloseableHttpResponse response = null; ???????try { ???????????response = getHttpResponse(url); ???????????result = EntityUtils.toString(response.getEntity(), DEFAULT_CHARSET); ???????????EntityUtils.consume(response.getEntity()); ???????} ???????catch (IOException e) { ???????????LOG.error("when getResponseXMLFromURL got an error"+e.getMessage()); ???????????Exceptions.throwException(e); ???????}finally{ ???????????try { ???????????????if(response!=null){ ???????????????????response.close(); ???????????????} ???????????} catch (IOException e) { ???????????????LOG.error("when getResponseXMLFromURL got an error" + e.getMessage()); ???????????} ???????} ???????return result; ???}public CloseableHttpResponse getHttpResponse(String url) throws IOException { ???????PoolingHttpClientConnectionManager cm = HttpConnectionManager.getInstance(); ???????int timeout = 5; ???????RequestConfig requestConfig = RequestConfig.custom() ???????????????.setConnectTimeout(timeout * 1000 * 60) ???????????????.setSocketTimeout(timeout * 1000 * 60).build(); ???????return httpClientCreator(cm,requestConfig).execute(new HttpGet(url)); ???}public CloseableHttpClient httpClientCreator(PoolingHttpClientConnectionManager cm,RequestConfig requestConfig){ ???????if(null != requestConfig){ ???????????return HttpClients.custom().setConnectionManager(cm).setDefaultRequestConfig(requestConfig).setProxy(new HttpHost(proxyUrl, Integer.valueOf(proxyPort))).build(); ???????} else { ???????????return HttpClients.custom().setConnectionManager(cm).setProxy(new HttpHost(proxyUrl, Integer.valueOf(proxyPort))).build(); ???????}参考：http://www.cnblogs.com/lyy-2016/p/6388663.html
httpClient4.5 closeableHttpClient用法
原文地址：https://www.cnblogs.com/unknows/p/8534713.html