Java实现post和get请求

GET请求：GET请求会向服务器发索取数据的请求，从而来获取信息，该请求就像数据库的select操作一样，只是用来查询一下数据，不会修改、增加数据，不会影响资源的内容，即该请求不会产生副作用。无论进行多少次操作，结果都是一样的。

 /**
      * 向指定URL发送GET方法的请求
      *
      */
     public static String get(String url) {
         BufferedReader in = null;
         try {
             URL realUrl = new URL(url);
             // 打开和URL之间的连接
             URLConnection connection = realUrl.openConnection();
             // 设置通用的请求属性
             connection.setRequestProperty("accept", "*/*");
             connection.setRequestProperty("connection", "Keep-Alive");
             connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
             connection.setConnectTimeout(5000);
             connection.setReadTimeout(5000);
             // 建立实际的连接
             connection.connect();
             // 定义 BufferedReader输入流来读取URL的响应
             in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
             StringBuffer sb = new StringBuffer();
             String line;
             while ((line = in.readLine()) != null) {
                 sb.append(line);
             }
             return sb.toString();
         } catch (Exception e) {
             LOG.error("Exception occur when send http get request!", e);
         }
         // 使用finally块来关闭输入流
         finally {
             try {
                 if (in != null) {
                     in.close();
                 }
             } catch (Exception e2) {
                 e2.printStackTrace();
             }
         }
         return null;
     }  

post请求：POST是向服务器端发送数据的，但是该请求会改变数据的种类等资源，就像数据库的insert操作一样，会创建新的内容。几乎目前所有的提交操作都是用POST请求的。

 /**
      * 发送HttpPost请求
      *
      * @param strURL
      *            服务地址
      * @param params
      *
      * @return 成功:返回json字符串<br/>
      */
     public static String jsonPost(String strURL, Map<String, String> params) {
         try {
             URL url = new URL(strURL);// 创建连接
             HttpURLConnection connection = (HttpURLConnection) url.openConnection();
             connection.setDoOutput(true);
             connection.setDoInput(true);
             connection.setUseCaches(false);
             connection.setInstanceFollowRedirects(true);
             connection.setRequestMethod("POST"); // 设置请求方式
             connection.setRequestProperty("Accept", "application/json"); // 设置接收数据的格式
             connection.setRequestProperty("Content-Type", "application/json"); // 设置发送数据的格式
             connection.connect();
             OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8编码
             out.append(JSONUtil.object2JsonString(params));
             out.flush();
             out.close();  

             int code = connection.getResponseCode();
             InputStream is = null;
             if (code == 200) {
                 is = connection.getInputStream();
             } else {
                 is = connection.getErrorStream();
             }  

             // 读取响应
             int length = (int) connection.getContentLength();// 获取长度
             if (length != -1) {
                 byte[] data = new byte[length];
                 byte[] temp = new byte[512];
                 int readLen = 0;
                 int destPos = 0;
                 while ((readLen = is.read(temp)) > 0) {
                     System.arraycopy(temp, 0, data, destPos, readLen);
                     destPos += readLen;
                 }
                 String result = new String(data, "UTF-8"); // utf-8编码
                 return result;
             }  

         } catch (IOException e) {
             LOG.error("Exception occur when send http post request!", e);
         }
         return "error"; // 自定义错误信息
     }