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  
    }