/**  * Copy Right Information   :    * Project                  :   * JDK version used         :    * Comments                 :    * Version                  : 1.01  * Author                   : Gordon Gu  * Modification history     : 2011  * Sr     Date       Modified By       Why & What is modified  * 1.     2011       Gordon Gu         new  **/ import java.io.*; import java.net.*; import sun.misc.BASE64Encoder; public class ServletCom { static String sessionId = ""; public static String getPicBASE64() { String picPath="g:/zhuge.jpg"; String content = ""; try { FileInputStream fileForInput = new FileInputStream(picPath); byte[] bytes = new byte[fileForInput.available()]; fileForInput.read(bytes); content = new sun.misc.BASE64Encoder().encode(bytes); // 具体的编码方法 fileForInput.close(); //System.out.println(content.length()); } catch (Exception e) { e.printStackTrace(); } return content; }    public static void main(String[] args) throws Exception {     // TODO Auto-generated method stub URL url = new URL("http://localhost:8080/PicDownload/valide.action"); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.setDoOutput(true); // Read from the connection. Default is true. connection.setDoInput(true); // Set the post method. Default is GET connection.setRequestMethod("POST"); // Post cannot use caches // Post 请求不能使用缓存 connection.setUseCaches(false); // This method takes effects to // every instances of this class. // URLConnection.setFollowRedirects是static函数，作用于所有的URLConnection对象。 // connection.setFollowRedirects(true); // This methods only // takes effacts to this // instance. // URLConnection.setInstanceFollowRedirects是成员函数，仅作用于当前函数 connection.setInstanceFollowRedirects(false); // Set the content type to urlencoded, // because we will write // some URL-encoded content to the // connection. Settings above must be set before connect! // 配置本次连接的Content-type，配置为application/x-www-form-urlencoded的 // 意思是正文是urlencoded编码过的form参数，下面我们可以看到我们对正文内容使用URLEncoder.encode // 进行编码 connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); // 连接，从postUrl.openConnection()至此的配置必须要在connect之前完成， // 要注意的是connection.getOutputStream会隐含的进行connect。 connection.connect(); Long sendTime = System.currentTimeMillis(); DataOutputStream out = new DataOutputStream(connection.getOutputStream()); // 要传的参数 String content = URLEncoder.encode("username", "UTF-8") + "=" + URLEncoder.encode("XXX", "UTF-8"); content += "&" + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode("XXXX", "UTF-8"); content += "&" + URLEncoder.encode("sendTime", "UTF-8") + "=" + URLEncoder.encode(sendTime.toString(), "UTF-8");  //得到图片的base64编码 content = content + "&" + URLEncoder.encode("file", "UTF-8") + "=" + URLEncoder.encode(getPicBASE64(), "UTF-8"); out.writeBytes(content); out.flush(); out.close(); // flush and close //Get Session ID String key = ""; if (connection != null) { for (int i = 1; (key = connection.getHeaderFieldKey(i)) != null; i++)  { if (key.equalsIgnoreCase("set-cookie")) { sessionId = connection.getHeaderField(key); sessionId = sessionId.substring(0, sessionId.indexOf(";")); } } }   // ------------------ read the SERVER RESPONSE try { DataInputStream inStream = new DataInputStream(connection.getInputStream()); String str; if((str = inStream.readLine()) != null) { System.out.println("Server response is: " + str); System.out.println(""); } inStream.close(); }  catch (IOException ioex)  { System.out.println("From (ServerResponse): " + ioex); } connection.disconnect(); } }