HttpClient 是 Apache Jakarta Common 下的子项目，可以用来提供高效的、最新的、功能丰富的支持 HTTP 协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本和建议。
使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可：
创建CloseableHttpClient对象。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。如果需要发送请求参数，可可调用setEntity(HttpEntity entity)方法来设置请求参数。setParams方法已过时（4.4.1版本）。调用HttpGet、HttpPost对象的setHeader(String name, String value)方法设置header信息，或者调用setHeaders(Header[] headers)设置一组header信息。调用CloseableHttpClient对象的execute(HttpUriRequest request)发送请求，该方法返回一个CloseableHttpResponse。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；调用CloseableHttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头。释放连接。无论执行方法是否成功，都必须释放连接
具体代码如下(HttpClient-4.4.1)：
/** * 简单httpclient实例* * @author arron* @date 11月11日 下午6:36:49 * @version 1.0 */public class SimpleHttpClientDemo {/*** 模拟请求* * @param url 资源地址* @param map 参数列表* @param encoding 编码* @return* @throws ParseException* @throws IOException*/public static String send(String url, Map<String,String> map,String encoding) throws ParseException, IOException{String body = "";//创建httpclient对象CloseableHttpClient client = HttpClients.createDefault();//创建post方式请求对象HttpPost httpPost = new HttpPost(url);//装填参数List<NameValuePair> nvps = new ArrayList<NameValuePair>();if(map!=null){for (Entry<String, String> entry : map.entrySet()) {nvps.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));}}//设置参数到请求对象中httpPost.setEntity(new UrlEncodedFormEntity(nvps, encoding));System.out.println("请求地址："+url);System.out.println("请求参数："+nvps.toString());//设置header信息//指定报文头【Content-type】、【User-Agent】httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");httpPost.setHeader("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");//执行请求操作，并拿到结果（同步阻塞）CloseableHttpResponse response = client.execute(httpPost);//获取结果实体HttpEntity entity = response.getEntity();if (entity != null) {//按指定编码转换结果实体为String类型body = EntityUtils.toString(entity, encoding);}EntityUtils.consume(entity);//释放链接 response.close();return body;}}
对于HTTPS的访问，采取绕过证书的策略：
/*** 绕过验证** @return* @throws NoSuchAlgorithmException * @throws KeyManagementException */public static SSLContext createIgnoreVerifySSL() throws NoSuchAlgorithmException, KeyManagementException {SSLContext sc = SSLContext.getInstance("SSLv3");// 实现一个X509TrustManager接口，用于绕过验证，不用修改里面的方法X509TrustManager trustManager = new X509TrustManager() {@Overridepublic void checkClientTrusted(java.security.cert.X509Certificate[] paramArrayOfX509Certificate,String paramString) throws CertificateException {}@Overridepublic void checkServerTrusted(java.security.cert.X509Certificate[] paramArrayOfX509Certificate,String paramString) throws CertificateException {}@Overridepublic java.security.cert.X509Certificate[] getAcceptedIssuers() {return null;}};sc.init(null, new TrustManager[] { trustManager }, null);return sc;}
然后修改原来的send方法：
/*** 模拟请求* * @param url 资源地址* @param map 参数列表* @param encoding 编码* @return* @throws NoSuchAlgorithmException * @throws KeyManagementException * @throws IOException * @throws ClientProtocolException */public static String send(String url, Map<String,String> map,String encoding) throws KeyManagementException, NoSuchAlgorithmException, ClientProtocolException, IOException {String body = "";//采用绕过验证的方式处理https请求SSLContext sslcontext = createIgnoreVerifySSL();// 设置协议http和https对应的处理socket链接工厂的对象Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create().register("http", PlainConnectionSocketFactory.INSTANCE).register("https", new SSLConnectionSocketFactory(sslcontext)).build();PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);HttpClients.custom().setConnectionManager(connManager);//创建自定义的httpclient对象CloseableHttpClient client = HttpClients.custom().setConnectionManager(connManager).build();// CloseableHttpClient client = HttpClients.createDefault();//创建post方式请求对象HttpPost httpPost = new HttpPost(url);//装填参数List<NameValuePair> nvps = new ArrayList<NameValuePair>();if(map!=null){for (Entry<String, String> entry : map.entrySet()) {nvps.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));}}//设置参数到请求对象中httpPost.setEntity(new UrlEncodedFormEntity(nvps, encoding));System.out.println("请求地址："+url);System.out.println("请求参数："+nvps.toString());//设置header信息//指定报文头【Content-type】、【User-Agent】httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");httpPost.setHeader("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");//执行请求操作，并拿到结果（同步阻塞）CloseableHttpResponse response = client.execute(httpPost);//获取结果实体HttpEntity entity = response.getEntity();if (entity != null) {//按指定编码转换结果实体为String类型body = EntityUtils.toString(entity, encoding);}EntityUtils.consume(entity);//释放链接 response.close();return body;}
但是，如果是自己用jdk或者其他工具生成的证书，还是希望用其他方式认证自签名的证书，这篇文章就来分享一下如何设置信任自签名的证书。当然你也可以参考官网示例中。
要想信任自签名的证书，必须得知道密钥库的路径及密钥库的密码。然后加载到程序来才可以。具体代码如下：
/*** 设置信任自签名证书** @param keyStorePath 密钥库路径* @param keyStorepass 密钥库密码* @return*/public static SSLContext custom(String keyStorePath, String keyStorepass){SSLContext sc = null;FileInputStream instream = null;KeyStore trustStore = null;try {trustStore = KeyStore.getInstance(KeyStore.getDefaultType());instream = new FileInputStream(new File(keyStorePath));trustStore.load(instream, keyStorepass.toCharArray());// 相信自己的CA和所有自签名的证书sc = SSLContexts.custom().loadTrustMaterial(trustStore, new TrustSelfSignedStrategy()).build();} catch (KeyStoreException | NoSuchAlgorithmException| CertificateException | IOException | KeyManagementException e) {e.printStackTrace();} finally {try {instream.close();} catch (IOException e) {}}return sc;}
然后修改原来的send方法：
/*** 模拟请求* * @param url 资源地址* @param map 参数列表* @param encoding 编码* @return* @throws ParseException* @throws IOException* @throws KeyManagementException * @throws NoSuchAlgorithmException * @throws ClientProtocolException */public static String send(String url, Map<String,String> map,String encoding) throws ClientProtocolException, IOException {String body = "";//tomcat是我自己的密钥库的密码，你可以替换成自己的//如果密码为空，则用"nopassword"代替SSLContext sslcontext = custom("D:\\keys\\wsriakey", "tomcat");// 设置协议http和https对应的处理socket链接工厂的对象Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create().register("http", PlainConnectionSocketFactory.INSTANCE).register("https", new SSLConnectionSocketFactory(sslcontext)).build();PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);HttpClients.custom().setConnectionManager(connManager);//创建自定义的httpclient对象CloseableHttpClient client = HttpClients.custom().setConnectionManager(connManager).build();// CloseableHttpClient client = HttpClients.createDefault();//创建post方式请求对象HttpPost httpPost = new HttpPost(url);//装填参数List<NameValuePair> nvps = new ArrayList<NameValuePair>();if(map!=null){for (Entry<String, String> entry : map.entrySet()) {nvps.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));}}//设置参数到请求对象中httpPost.setEntity(new UrlEncodedFormEntity(nvps, encoding));System.out.println("请求地址："+url);System.out.println("请求参数："+nvps.toString());//设置header信息//指定报文头【Content-type】、【User-Agent】httpPost.setHeader("Content-type", "application/x-www-form-urlencoded");httpPost.setHeader("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");//执行请求操作，并拿到结果（同步阻塞）CloseableHttpResponse response = client.execute(httpPost);//获取结果实体HttpEntity entity = response.getEntity();if (entity != null) {//按指定编码转换结果实体为String类型body = EntityUtils.toString(entity, encoding);}EntityUtils.consume(entity);//释放链接 response.close();return body;}
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