Http使用post方式提交数据（使用java标准接口）

本文内容：使用java标准接口，实现http用post方式提交数据。

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程序组成部分：

1.客户端用eclipse HttpUtils.java 标准java接口，实现http用post方式提交数据。 （用post方式提交 username 和 password）

2.服务器端用myeclipse+tomcat 对客户端请求进行相应。(若用户名密码正确，则返回字符串"login is success !" ,不正确则返回字符串“login is fail !”)

重点注意点：

1. public static String sendPostMessage(Map<String,String> params , String encode)

    目的: 在客户端向服务器端发送 数据 params , 最终获取从服务器返回的输入流，最终将该输入流转换成字符串。注意使用标准java接口如何实现http的post请求，成功与服务器连接，并且获得从服务器端响应返回的数据。

2. public String String changInputStream(InputStream inputStream , String encode)

    目的: 将一个输入流按照指定编码方式转变成一个字符串。(本例中是指，将从服务器端返回的输入流InputStream转变成一个字符串String，编码方式是encode方式)

3. Map<String ,String> 的实例化方法及迭代方法

  Map  的实例化方法：

  Map<String, String> params = new HashMap<String, String>();
  params.put("username", "admin");
  params.put("password", "123");

 

   Map 的迭代方法：

 StringBuffer stringBuffer = new StringBuffer();

 
   for (Map.Entry<String, String> entry : params.entrySet()) {
    try {
     stringBuffer
       .append(entry.getKey())
       .append("=")
       .append(URLEncoder.encode(entry.getValue(), encode))
       .append("&");

    } catch (UnsupportedEncodingException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
   
   }
   // 删掉最后一个 & 字符
   stringBuffer.deleteCharAt(stringBuffer.length() - 1);

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程序思路：

1. 客户端建立http链接httpURLConnection，使用OutputStream向服务器传入数据

2. 获得从服务器端返回的输入流InputStream

3. 将InputStream转换成字符串String

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程序运行效果：

1.客户端运行效果

2. 服务器端运行结果

关键代码：

1. 客户端 HttpUtils.java

package com.http.post;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.io.UnsupportedEncodingException;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.net.URLEncoder;import java.util.HashMap;import java.util.Map;public class HttpUtils {// 表示服务器端的urlprivate static String PATH = "http://192.168.0.100:8080/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 blocke.printStackTrace();}}/* * params 填写的URL的参数 encode 字节编码 */public static String sendPostMessage(Map<String, String> params,String encode) {StringBuffer stringBuffer = new StringBuffer();if (params != null && !params.isEmpty()) {for (Map.Entry<String, String> entry : params.entrySet()) {try {stringBuffer.append(entry.getKey()).append("=").append(URLEncoder.encode(entry.getValue(), encode)).append("&");} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();}}// 删掉最后一个 & 字符stringBuffer.deleteCharAt(stringBuffer.length() - 1);System.out.println("-->>" + stringBuffer.toString());try {HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();httpURLConnection.setConnectTimeout(3000);httpURLConnection.setDoInput(true);// 从服务器获取数据httpURLConnection.setDoOutput(true);// 向服务器写入数据// 获得上传信息的字节大小及长度byte[] mydata = stringBuffer.toString().getBytes();// 设置请求体的类型httpURLConnection.setRequestProperty("Content-Type","application/x-www-form-urlencoded");httpURLConnection.setRequestProperty("Content-Lenth",String.valueOf(mydata.length));// 获得输出流，向服务器输出数据OutputStream outputStream = (OutputStream) httpURLConnection.getOutputStream();outputStream.write(mydata);// 获得服务器响应的结果和状态码int responseCode = httpURLConnection.getResponseCode();if (responseCode == 200) {// 获得输入流，从服务器端获得数据InputStream inputStream = (InputStream) httpURLConnection.getInputStream();return (changeInputStream(inputStream, encode));}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}return "";}/* * // 把从输入流InputStream按指定编码格式encode变成字符串String */public static String changeInputStream(InputStream inputStream,String encode) {// ByteArrayOutputStream 一般叫做内存流ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();byte[] data = new byte[1024];int len = 0;String result = "";if (inputStream != null) {try {while ((len = inputStream.read(data)) != -1) {byteArrayOutputStream.write(data, 0, len);}result = new String(byteArrayOutputStream.toByteArray(), encode);} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}return result;}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubMap<String, String> params = new HashMap<String, String>();params.put("username", "admin");params.put("password", "123");String result = sendPostMessage(params, "utf-8");System.out.println("-result->>" + result);}}

服务器端servlet: LoginAction.java

package com.login.manager;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;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");//客户端 HttpUtils并没有写request方法是post ,但服务器端可自动识别String method = request.getMethod();System.out.println("request method :"+method);PrintWriter out = response.getWriter();String username = request.getParameter("username");System.out.println("-username->>"+username);String password = request.getParameter("password");System.out.println("-password->>"+password);if (username.equals("admin") && password.equals("123")) {// 表示服务器段返回的结果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}}