伺服器與資料庫建立連線，將從瀏覽器得到的資訊與資料庫中的資訊相比較，如果有了，就顯示登陸成功，如果沒有，就顯示登入失敗：

package com.lingzhuo.test;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import
 
 javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ServletTest
 */
@WebServlet("/ServletTest")
public class ServletTest extends HttpServlet {
    private static final long serialVersionUID = 1
 
L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public ServletTest() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws
 
 ServletException, IOException {
        // TODO Auto-generated method stub
        String name = request.getParameter("name");
        String password = request.getParameter("password");
//      try {
//          Thread.sleep(1000);
//      } catch (InterruptedException e) {
//          // TODO Auto-generated catch block
//          e.printStackTrace();
//      }
//      name= Encoding.doEncoding(name);
//      password = Encoding.doEncoding(password);
        String s = "";

        System.out.println("使用者名稱: "+name+" "+"密碼: "+password);
        Connection con = MySQL.newInstance().getCon();
        try {
            PreparedStatement prea = con.prepareStatement("select * from user where username = ? and password=?");
            prea.setString(1, name);
            prea.setString(2, password);
            ResultSet set = prea.executeQuery();
            set.last();
            int num = set.getRow();
            if(num==1){
                s = "登陸成功";
            }else{
                s = "登入失敗";
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
//      response.getWriter().append("Served at: ").append(request.getContextPath());
        response.setHeader("Content-type", "text/html;charset=UTF-8");
//      response.getWriter().append("使用者名稱: "+name+"密碼: "+password);

        response.getWriter().append(s);
    }
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}