1、什么是httpclient

      HttpClient 是 Apache Jakarta Common 下的子项目，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。

      HttpClient特性：基于标准、纯净的Java语言。实现了Http1.0和Http1.1。支持HTTPS协议。通过Http代理建立透明的连接。

      下载地址：http://hc.apache.org/

2、使用方法

使用HttpClient发送请求、接收响应很简单，一般需要如下几步即可。        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。

3、实例

添加依赖 <!-- httpclient --> <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>${httpclient.version}</version> </dependency> 3.1、get 请求抓取网页信息

/*get 请求抓取网页信息*/ @Test public void doGet() throws Exception { //创建一个httpclient对象 CloseableHttpClient httpClient = HttpClients.createDefault(); //创建一个GET对象 HttpGet get = new HttpGet("http://www.sogou.com"); //执行请求 CloseableHttpResponse response = httpClient.execute(get); //取响应的结果 int statusCode = response.getStatusLine().getStatusCode(); System.out.println(statusCode); HttpEntity entity = response.getEntity(); String string = EntityUtils.toString(entity, "utf-8"); System.out.println(string); //关闭httpclient response.close(); httpClient.close(); }  

3.2、带参数的get请求

/*带参数的get 请求*/ @Test public void doGetWithParam() throws Exception{ //创建一个httpclient对象 CloseableHttpClient httpClient = HttpClients.createDefault(); //创建一个uri对象 URIBuilder uriBuilder = new URIBuilder("http://www.sogou.com/web"); uriBuilder.addParameter("query", "花千骨"); HttpGet get = new HttpGet(uriBuilder.build()); //执行请求 CloseableHttpResponse response = httpClient.execute(get); //取响应的结果 int statusCode = response.getStatusLine().getStatusCode(); System.out.println(statusCode); HttpEntity entity = response.getEntity(); String string = EntityUtils.toString(entity, "utf-8"); System.out.println(string); //关闭httpclient response.close(); httpClient.close(); }

3.3、post请求

/*post 请求*/ @Test public void doPost() throws Exception { CloseableHttpClient httpClient = HttpClients.createDefault(); //创建一个post对象 HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.html"); //执行post请求 CloseableHttpResponse response = httpClient.execute(post); String string = EntityUtils.toString(response.getEntity()); System.out.println(string); response.close(); httpClient.close(); }

SpringMVC的Controller本地模拟：http://localhost:8082/httpclient/post.html 

//测试：乱码produces= MediaType.TEXT_PLAIN_VALUE+";charset=utf-8" @RequestMapping(value="/httpclient/post", method= RequestMethod.POST, produces= MediaType.TEXT_PLAIN_VALUE+";charset=utf-8") @ResponseBody public String testPost(String username, String password) { String result = "username:" + username + "\tpassword:" + password; System.out.println(result); return "username:" + username + ",password:" + password; }

3.4、带参数的post请求

/*post 带参数请求*/ @Test public void doPostWithParam() throws Exception{ CloseableHttpClient httpClient = HttpClients.createDefault(); //创建一个post对象 HttpPost post = new HttpPost("http://localhost:8082/httpclient/param.html"); //创建一个Entity。模拟一个表单 List<NameValuePair> kvList = new ArrayList<>(); kvList.add(new BasicNameValuePair("username", "zhangsan")); kvList.add(new BasicNameValuePair("password", "123")); //包装成一个Entity对象 StringEntity entity = new UrlEncodedFormEntity(kvList, "utf-8"); //设置请求的内容 post.setEntity(entity); //执行post请求 CloseableHttpResponse response = httpClient.execute(post); String string = EntityUtils.toString(response.getEntity()); System.out.println(string); response.close(); httpClient.close(); } SpringMVC的Controller本地模拟：http://localhost:8082/httpclient/param 的Controller

//测试 @RequestMapping(value = "/httpclient/param",method = RequestMethod.POST) @ResponseBody public String testPostParam(String username,String password){ return "username:"+ username + "\tpassword:" +password; }