编程开发练习：是用Servlet实现用户登录界面

编程开发练习：是用Servlet实现用户登录界面，今天学习的是用Servlet实现用户登录界面。
??index.jsp页面的代码还是07-08的代码
??main.jsp页面的代码是新建页面的代码
??今天主要学习连接数据库
??下面是今天的代码

//BaseDao.java
package dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

// 负责完成数据库的操作
public class BaseDao {
    // 增 删 查 改
    // 为了能够操作数据库，我们需要首先获得一个操作数据库的代理
    /**
     * 所有数据库操作可以分为四步，
     * 第一步 加载驱动
     * 第二步 获取连接
     * 第三步 执行操作
     * 第四步 得到结果
     * 
     * */

    public int getData(String sql){
        int result=0;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/sqsj","root","");
            Statement stmt = con.createStatement();
            ResultSet rs=stmt.executeQuery(sql);
            if(rs.next()){
                result = 1;
            }
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return result;
    }
}

在这里，连接数据库的主要代码是：

Class.forName("com.mysql.jdbc.Driver");
Connection  con= DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/sqsj","root","");
Statement stmt = con.createStatement();
ResultSet rs=stmt.executeQuery(sql);

// LogServlet.java  这是一个Servlet类
package action;

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;

import dao.BaseDao;

public class LogServlet extends HttpServlet {
    BaseDao bd = new BaseDao();
    /**
         * The doGet method of the servlet. 

         *
         * 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 {

        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        PrintWriter out = response.getWriter();     // 获取返回输出
        //获取页面输入信息
        String uname=request.getParameter("uname");
        String upwd=request.getParameter("upwd");
        String sql="select * from users where uname ='"+uname+"'and upwd='"+upwd+"'";
//      System.out.println(request.getLocalAddr());  获取IP地址 查javaEE帮助文档

        if(bd.getData(sql)>0)
            response.sendRedirect("../main.jsp");   // 重定向
        else{
            out.print("<script>alert('用户名或密码错误');history.back();</script>");
        }
        out.flush();
        out.close();
    }

    /**
         * The doPost method of the servlet. 

         *
         * 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 {
        doGet(request,response);    // Alt+/  智能提示
    }

}

在MyEclipse的文件如下:

此外，连接数据库还需要导入数据库的jar包，我在这里用的是MySql的数据库，我的数据库的界面如下

其中的测试数据如下：

以上，就是今天所学习的内容。