Servlet及JDBC、dao简单运用

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Servlet

在服务器上运行以处理客户端请求并作出响应的程序。

init() . service() . destroy()

主要使用的是HttpServlet ,（主要处理HTTP协议的请求和响应）

doGet（）以get请求调用时使用

doPost（）以post请求调用时使用

JDBC

Jdbc是java数据库连接技术的简称

Jdbc API：和数据库建立连接、执行SQL语句、处理结果。

查询用executeQuery（）

增删改要用executeUpdate（）

DAO：数据存取对象

分层模式：是一种结构模式（表示层、业务逻辑层、数据库访问层）

表示层依赖业务逻辑层，业务逻辑层依赖数据库访问层

上层依赖下一层，下层不能调用上层。（不能跨层）

例子：

1.首先建一个dao包，然后创建一个类--BaseDao.java (里面放入与数据库相连接的代码等)

package second.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

public class BaseDao {

   private final String URL="jdbc:oracle:thin:@127.0.0.1:1521:orcl";
   private final String USER="*****";
   private final String PWD="******";

   private Connection conn;
   private PreparedStatement pstmt;
   private ResultSet rs;

   static{
       try {
           Class.forName("oracle.jdbc.driver.OracleDriver");
       } catch (ClassNotFoundException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }
   }

   private Connection getConnection(){
       Connection conn=null;
       try {
           conn=DriverManager.getConnection(URL,USER,PWD);
       } catch (SQLException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }
       return conn;
   }

   public int executeUpdate(String sql,List<Object> params){
       int count=0;
       //数据库连接
       conn=getConnection();

       try {
           pstmt=conn.prepareStatement(sql);
           //设置参数
           if(params!=null){
               for(int i=0;i<params.size();i++){
                   pstmt.setObject(i+1, params.get(i));
               }
           }
           count=pstmt.executeUpdate();

       } catch (SQLException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       } finally{
           closeAll();
       }

       return count;
   }

   public ResultSet executeQuery(String sql,List<Object> params){
       conn=getConnection();

       try {
           pstmt=conn.prepareStatement(sql);
           if(params!=null){
               for(int i=0;i<params.size();i++){
                   pstmt.setObject(i+1, params.get(i));
               }
           }

           rs= pstmt.executeQuery();
       } catch (SQLException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }


       return rs;
   }

   public void closeAll(){

       try {
           if(rs!=null){
               rs.close();
               rs=null;
           }
           if(pstmt!=null){
               pstmt.close();
               pstmt=null;

           }
           if(conn!=null){
               conn.close();
               conn=null;
           }
       } catch (SQLException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }
   }


}

2.数据库中含有相应的表（user）及类User ， servlet中的内容

package second.servlet;

import java.io.IOException;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import second.entity.Cusinfo;
import second.entity.User;
import second.service.CusinfoService;
import second.service.LoginBiz;
import second.service.impl.CusinfoServiceImpl;
import second.service.impl.LoginBizImpl;

public class LoginServlet extends HttpServlet {

   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse resp)
           throws ServletException, IOException {
       // TODO Auto-generated method stub
       doPost(req, resp);
   }

   @Override
   protected void doPost(HttpServletRequest req, HttpServletResponse resp)
           throws ServletException, IOException {
       req.setCharacterEncoding("utf-8");
       String name=req.getParameter("username");
       String pwd=req.getParameter("userpwd");

       LoginBiz loginBiz= new LoginBizImpl();
       User user=loginBiz.login(name, pwd);
       if(user!=null){

           req.setAttribute("cusinfos", list);
           //转发
           RequestDispatcher rd = req.getRequestDispatcher("/login/dilogin_success.jsp");
           rd.forward(req, resp);
       }else{
           //重定向
           resp.sendRedirect(req.getContextPath()+"/login/login_fail.jsp");
       }
   }

}

package second.entity;

public class User {
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public String getPwd() {
       return pwd;
   }
   public void setPwd(String pwd) {
       this.pwd = pwd;
   }
   private String name;
   private String pwd;

}

3.相应的接口及其实现

①
import second.entity.User;

public interface LoginBiz {
public User login(String name,String pwd);
}

②

import second.dao.AccountDao;
import second.dao.impl.AccountDaoImpl;
import second.entity.User;
import second.service.LoginBiz;

public class LoginBizImpl implements LoginBiz {

   private AccountDao accountDao =new AccountDaoImpl() ;

   @Override
   public User login(String name, String pwd) {
       User user = accountDao.findUserByName(name);
       if(user!=null && user.getPwd().equals(pwd)){
           return user;
       }
       return null;
   }
}

③

package second.dao;

import second.entity.User;

public interface AccountDao {
public User findUserByName(String name);
}

④

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import second.dao.AccountDao;
import second.dao.BaseDao;
import second.entity.User;

public class AccountDaoImpl extends BaseDao implements AccountDao{

   public User findUserByName(String name){
       User user = null;
       String select ="select uname,pwd from accounts where uname=?";
       List<Object> params = new ArrayList<Object>();
       params.add(name);

       ResultSet rs= this.executeQuery(select,params);

       try {
           if(rs.next()){
               user = new User();
               user.setName(rs.getString("uname"));
               user.setPwd(rs.getString("pwd"));
           }
       } catch (SQLException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }finally{
           this.closeAll();
       }
       return user;

   }
}

4.jsp中的内容，有相应的验证

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">

    <title>登录页面</title>
    <script type="text/javascript" src="<%=request.getContextPath()%>/js/jquery-1.10.2.js"></script>
    <script type="text/javascript">
       $(function(){
           $("#myname").blur(function(){
               var uname=$("#myname").val();
               if(uname==""){
                   $("#nameTip").html("用户名不能为空！！");
                   //alert("用户名不能为空！！");
                   return;
               }else{
                   $("#nameTip").html("   ");
               }
           });
           $("#mypwd").blur(function(){
               var upwd=$("#mypwd").val();
               if(upwd==""){
                   $("#pwdTip").html("密码不能为空！！！");
                   return;
               }else{
                   $("pwdTip").html(" ");
               }
           });
       });
    </script>

</head>

<body>
    <form action="<%=request.getContextPath()%>/loginServlet.action" method="post" >
        <table>
            <tr>
                <td>用户名：</td>
                <td>
                    <input type="text" name="username" id="myname"><span id="nameTip"></span>
                </td>
            </tr>
            <tr>
                <td>密码：</td>
                <td>
                    <input type="password" name="userpwd" id="mypwd"><span id="pwdTip"></span>
                </td>
            </tr>
            <tr>
                <td>
                    <input type="submit" value="登录" >
                </td>
                <td>
                    <input type="reset" value="重置">
                </td>
            </tr>
        </table>
    </form>
</body>
</html>

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