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url
  private 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 block
      e.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 block
          e.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 block
        e.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 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", "123");
    String result = sendPostMessage(params, "utf-8");
    System.out.println("-result->>" + result);

  }

}

服务器端: 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
  }

}