HttpClient 实例（1）

[size=large][b]1：概述[/b][/size]
HttpClient是HttpComponents（简称为hc)项目其中的一部份,访问地址：http://hc.apache.org/
[img]http://dl.iteye.com/upload/attachment/584521/ddaadc93-0ccc-3248-95d2-4a0c5820f9a6.png[/img]
HttpClient是一个代码级的Http客户端工具,可以使用它模拟浏览器向Http服务器发送请求。使用HttpClient还需要HttpCore.后者包括Http请求与Http响应的代码封装。

[img]http://dl.iteye.com/upload/attachment/584523/69c45455-7ccd-3229-b3ea-802549771684.png[/img]

[size=large][b]2：HttpGet[/b][/size]

    public final static void main(String[] args) throws Exception {          HttpClient httpclient = new DefaultHttpClient();          try {              HttpGet httpget = new HttpGet("http://www.apache.org/");              System.out.println("executing request " + httpget.getURI());              HttpResponse response = httpclient.execute(httpget);              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("----------------------------------------");  

            InputStream inSm = entity.getContent();              Scanner inScn = new Scanner(inSm);              while (inScn.hasNextLine()) {                  System.out.println(inScn.nextLine());              }              // Do not feel like reading the response body              // Call abort on the request object  关闭            httpget.abort();          } finally {              // When HttpClient instance is no longer needed,              // shut down the connection manager to ensure              // immediate deallocation of all system resources  关闭            httpclient.getConnectionManager().shutdown();          }      }

[img]http://dl.iteye.com/upload/attachment/584532/38d19a0e-b98f-3d13-a209-fcff5105bcb7.png[/img]
[b]httpcore：EntityUtils.toString(httpEntity)[/b]

读取response响应内容部分，也可以借助于 httpcore-4.1.2.jar 里面的
String content = EntityUtils.toString(httpEntity);
具体：

       public class Demo1 {  

        /**          * 用 get 方法访问 www.apache.org 并返回内容          *          * @param args          */          public static void main(String[] args) {              //创建默认的 HttpClient 实例              HttpClient httpClient = new DefaultHttpClient();              try {                  //创建 httpUriRequest 实例                  HttpGet httpGet = new HttpGet("http://www.apache.org/");                  System.out.println("uri=" + httpGet.getURI());  

                //执行 get 请求                  HttpResponse httpResponse = httpClient.execute(httpGet);  

                //获取响应实体                  HttpEntity httpEntity = httpResponse.getEntity();                  //打印响应状态                  System.out.println(httpResponse.getStatusLine());                  if (httpEntity != null) {                      //响应内容的长度                      long length = httpEntity.getContentLength();                      //响应内容                      String content = EntityUtils.toString(httpEntity);  

                    System.out.println("Response content length:" + length);                      System.out.println("Response content:" + content);                  }  

                //有些教程里没有下面这行                  httpGet.abort();              } catch (Exception e) {                  e.printStackTrace();              } finally {                  //关闭连接，释放资源                  httpClient.getConnectionManager().shutdown();              }          }      }

执行结果：
[img]http://dl.iteye.com/upload/attachment/584532/38d19a0e-b98f-3d13-a209-fcff5105bcb7.png[/img]

[b]httpget.setHeader[/b]
1:分析请求包中这六个头信息
[img]http://dl.iteye.com/upload/attachment/584558/ab5b639c-8f24-394e-a74a-ab0b1dd4f2b5.png[/img]
2:代码

       public static void main(String[] args) {          HttpClient httpClient = new DefaultHttpClient();          try {              HttpGet httpget = new HttpGet("http://www.iteye.com");  

            httpget.setHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");              httpget.setHeader("Accept-Language", "zh-cn,zh;q=0.5");              httpget.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 5.1; rv:7.0.1) Gecko/20100101 Firefox/7.0.1)");              httpget.setHeader("Accept-Encoding", "gzip, deflate");              httpget.setHeader("Accept-Charset", "GB2312,utf-8;q=0.7,*;q=0.7");              httpget.setHeader("Host", "www.iteye.com");              httpget.setHeader("Connection", "Keep-Alive");  

            HttpResponse response = httpClient.execute(httpget);              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("----------------------------------------");  

            InputStream inSm = entity.getContent();              Scanner inScn = new Scanner(inSm);              while (inScn.hasNextLine()) {                  System.out.println(inScn.nextLine());              }              // Do not feel like reading the response body              // Call abort on the request object              httpget.abort();          } catch (Exception e) {              e.printStackTrace();          } finally {              // When HttpClient instance is no longer needed,              // shut down the connection manager to ensure              // immediate deallocation of all system resources              httpClient.getConnectionManager().shutdown();          }      }

3：效果[img]http://dl.iteye.com/upload/attachment/584560/6c810c00-ed43-3260-b650-6e6f2d2e1486.png[/img]
以上乱码是由于
[color=darkred]httpget.setHeader("Accept-Encoding", "gzip, deflate");[/color]
注释掉这行就行

[b]用post方法访问本地应用根据传递参数不同，返回不同结果[/b]
1：web.xml

    <servlet>          <servlet-name>Test1Servlet</servlet-name>          <servlet-class>demo.servlet.Test1Servlet</servlet-class>      </servlet>      <servlet-mapping>          <servlet-name>Test1Servlet</servlet-name>          <url-pattern>/test1Servlet</url-pattern>      </servlet-mapping>

2：Test1Servlet.java

public class Test1Servlet extends HttpServlet {      @Override      protected void doPost(HttpServletRequest request, HttpServletResponse response)              throws ServletException, IOException {          //接收地址栏参数          String param1 = request.getParameter("param1");          //输出          response.setContentType("text/html;charset=UTF-8");          PrintWriter out = response.getWriter();          out.write("你传递来的参数param1=" + param1);          out.close();      }  }

3：Demo2.java

public class Demo2 {  

    /**      * 用post方法访问本地应用根据传递参数不同，返回不同结果      *      * @param args      */      public static void main(String[] args) {          //创建默认的 HttpClient 实例          HttpClient httpClient = new DefaultHttpClient();  

        HttpPost httpPost = new HttpPost("http://localhost:86/test1Servlet");  

        List<NameValuePair> formParams = new ArrayList<NameValuePair>();          formParams.add(new BasicNameValuePair("param1", "刘文涛"));          UrlEncodedFormEntity urlEncodedFormEntity;  

        try {              urlEncodedFormEntity = new UrlEncodedFormEntity(formParams, "UTF-8");              httpPost.setEntity(urlEncodedFormEntity);              System.out.println("execurting request:" + httpPost.getURI());              HttpResponse httpResponse = null;              httpResponse = httpClient.execute(httpPost);              HttpEntity httpEntity = httpResponse.getEntity();              if (httpEntity != null) {                  String content = EntityUtils.toString(httpEntity, "UTF-8");                  System.out.println("Response content:" + content);              }          } catch (ClientProtocolException e) {              e.printStackTrace();          } catch (UnsupportedEncodingException e) {              e.printStackTrace();          } catch (IOException e) {              e.printStackTrace();          } finally {              //关闭连接，释放资源              httpClient.getConnectionManager().shutdown();          }      }  }

结果：[img]http://dl.iteye.com/upload/attachment/0062/3722/d493017f-691c-39b0-ad45-03f86db6bde0.png[/img]

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