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* 每个HTTP-GET和HTTP-POST都由一系列HTTP请求头组成，这些请求头定义了客户端从服务器请求了什么，而响应则是由一系列HTTP请求数据和响应数据组成，如果请求成功则返回响应的数据。
* HTTP-GET以使用MIME类型application/x-www-form-urlencoded的urlencoded文本的格式传递参数。Urlencoding是一种字符编码，保证被传送的参数由遵循规范的文本组成，例如一个空格的编码是"%20"。附加参数还能被认为是一个查询字符串。
* 与HTTP-GET类似，HTTP-POST参数也是被URL编码的。然而，变量名/变量值不作为URL的一部分被传送，而是放在实际的HTTP请求消息内部被传送。
* GET和POST之间的主要区别
1、GET是从服务器上获取数据，POST是向服务器传送数据。
2、在客户端， GET方式在通过URL提交数据，数据在URL中可以看到；POST方式，数据放置在HTML HEADER内提交
3、对于GET方式，服务器端用Request.QueryString获取变量的值，对于POST方式，服务器端用Request.Form获取提交的数据。
4、GET方式提交的数据最多只能有1024字节，而POST则没有此限制
5、安全性问题。正如在（2）中提到，使用 GET 的时候，参数会显示在地址栏上，而 POST 不会。所以，如果这些数据是中文数据而且是非敏感数据，那么使用 GET ；如果用户输入的数据不是中文字符而且包含敏感数据，那么还是使用 POST为好
* URL的定义和组成
Uniform Resource Locator 统一资源定位符
URL的组成部分：http://www.mbalib.com/china/index.htm
http://：代表超文本传输协议
www：代表一个万维网服务器
mbalib.com/：服务器的域名，或服务器名称
China/：子目录，类似于我们的文件夹
Index.htm:是文件夹中的一个文件
/china/index.htm统称为URL路径
服务器端
public class LoginAction extends HttpServlet { /** * Constructor of the object. */ public LoginAction() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); request.setCharacterEncoding("utf-8"); response.setCharacterEncoding("utf-8"); PrintWriter out = response.getWriter(); String username = request.getParameter("username"); System.out.println("-username->>"+username); String pswd = request.getParameter("password"); System.out.println("-password->>"+pswd); if(username.equals("admin")&&pswd.equals("123")){ //表示服务器端返回的结果 out.print("login is success!!!!"); }else{ out.print("login is fail!!!"); } out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }
HTTP-GET方式
public class HttpUtils { private static String URL_PATH = "http://192.168.0.102:8080/myhttp/pro1.png"; public HttpUtils() { // TODO Auto-generated constructor stub } public static void saveImageToDisk() { InputStream inputStream = getInputStream(); byte[] data = new byte[1024]; int len = 0; FileOutputStream fileOutputStream = null; try { fileOutputStream = new FileOutputStream("C:\\test.png"); while ((len = inputStream.read(data)) != -1) { fileOutputStream.write(data, 0, len); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } if (fileOutputStream != null) { try { fileOutputStream.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } /** * 获得服务器端的数据,以InputStream形式返回 * @return */ public static InputStream getInputStream() { InputStream inputStream = null; HttpURLConnection httpURLConnection = null; try { URL url = new URL(URL_PATH); if (url != null) { httpURLConnection = (HttpURLConnection) url.openConnection(); // 设置连接网络的超时时间 httpURLConnection.setConnectTimeout(3000); httpURLConnection.setDoInput(true); // 表示设置本次http请求使用GET方式请求 httpURLConnection.setRequestMethod("GET"); int responseCode = httpURLConnection.getResponseCode(); if (responseCode == 200) { // 从服务器获得一个输入流 inputStream = httpURLConnection.getInputStream(); } } } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return inputStream; } public static void main(String[] args) { // 从服务器获得图片保存到本地 saveImageToDisk(); } }
HTTP-POST(Java接口)方式
public class HttpUtils { // 请求服务器端的url private static String PATH = "http://192.168.0.102:8080/myhttp/servlet/LoginAction"; private static URL url; public HttpUtils() { // TODO Auto-generated constructor stub } static { try { url = new URL(PATH); } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } /** * @param params * 填写的url的参数 * @param encode * 字节编码 * @return */ public static String sendPostMessage(Map<String, String> params, String encode) { // 作为StringBuffer初始化的字符串 StringBuffer buffer = new StringBuffer(); try { if (params != null && !params.isEmpty()) { for (Map.Entry<String, String> entry : params.entrySet()) { // 完成转码操作 buffer.append(entry.getKey()).append("=").append( URLEncoder.encode(entry.getValue(), encode)) .append("&"); } buffer.deleteCharAt(buffer.length() - 1); } // System.out.println(buffer.toString()); // 删除掉最有一个& System.out.println("-->>"+buffer.toString()); HttpURLConnection urlConnection = (HttpURLConnection) url .openConnection(); urlConnection.setConnectTimeout(3000); urlConnection.setRequestMethod("POST"); urlConnection.setDoInput(true);// 表示从服务器获取数据 urlConnection.setDoOutput(true);// 表示向服务器写数据 // 获得上传信息的字节大小以及长度 byte[] mydata = buffer.toString().getBytes(); // 表示设置请求体的类型是文本类型 urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); urlConnection.setRequestProperty("Content-Length", String.valueOf(mydata.length)); // 获得输出流,向服务器输出数据 OutputStream outputStream = urlConnection.getOutputStream(); outputStream.write(mydata,0,mydata.length); outputStream.close(); // 获得服务器响应的结果和状态码 int responseCode = urlConnection.getResponseCode(); if (responseCode == 200) { return changeInputStream(urlConnection.getInputStream(), encode); } } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return ""; } /** * 将一个输入流转换成指定编码的字符串 * * @param inputStream * @param encode * @return */ private static String changeInputStream(InputStream inputStream, String encode) { // TODO Auto-generated method stub ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); byte[] data = new byte[1024]; int len = 0; String result = ""; if (inputStream != null) { try { while ((len = inputStream.read(data)) != -1) { outputStream.write(data, 0, len); } result = new String(outputStream.toByteArray(), encode); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return result; } /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub Map<String, String> params = new HashMap<String, String>(); params.put("username", "admin"); params.put("password", "1234"); String result = HttpUtils.sendPostMessage(params, "utf-8"); System.out.println("--result->>" + result); } }
HTTP-POST(Apache接口)方式
public class HttpUtils { public HttpUtils() { // TODO Auto-generated constructor stub } public static String sendHttpClientPost(String path, Map<String, String> map, String encode) { List<NameValuePair> list = new ArrayList<NameValuePair>(); if (map != null && !map.isEmpty()) { for (Map.Entry<String, String> entry : map.entrySet()) { list.add(new BasicNameValuePair(entry.getKey(), entry .getValue())); } } try { // 实现将请求的参数封装到表单中,请求体重 UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list, encode); // 使用Post方式提交数据 HttpPost httpPost = new HttpPost(path); httpPost.setEntity(entity); // 指定post请求 DefaultHttpClient client = new DefaultHttpClient(); HttpResponse httpResponse = client.execute(httpPost); if (httpResponse.getStatusLine().getStatusCode() == 200) { return changeInputStream(httpResponse.getEntity().getContent(), encode); } } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClientProtocolException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return ""; } /** * 将一个输入流转换成指定编码的字符串 * * @param inputStream * @param encode * @return */ public static String changeInputStream(InputStream inputStream, String encode) { // TODO Auto-generated method stub ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); byte[] data = new byte[1024]; int len = 0; String result = ""; if (inputStream != null) { try { while ((len = inputStream.read(data)) != -1) { outputStream.write(data, 0, len); } result = new String(outputStream.toByteArray(), encode); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return result; } /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub String path = "http://192.168.0.102:8080/myhttp/servlet/LoginAction"; Map<String, String> params = new HashMap<String, String>(); params.put("username", "admin"); params.put("password", "123"); String result = HttpUtils.sendHttpClientPost(path, params, "utf-8"); System.out.println("-->>"+result); } }
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原文地址：http://www.cnblogs.com/anni-qianqian/p/5568588.html
