J2EE知识点1 - Servlet练习（登陆及查询） - 《Java笔记》

//告诉request才用如下的字符集进行组合
req.setCharacterEncoding(“UTF-8”);
//_设置服务器向浏览器发送响应信息的字符集
_resp.setCharacterEncoding(“UTF-8”);
这两条语句很重要，不加上很可能出现乱码问题

返回操作代码：**

<script type="text/javascript">
            window.onload=function () {
                var inputElement=document.getElementById("back");
                inputElement.onclick=function () {
                    window.history.back();
                }
            }
        </script>

AtmForServlet.zip

package controller;

import service.AtmService;
import util.MySpring;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class LoginController extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        String username=req.getParameter("username");
        String password= req.getParameter("password");
        AtmService atmService= MySpring.getJavaBean("service.AtmService");
        String result=atmService.login(username,password);
        System.out.println(result);

        //设置服务器向浏览器发送响应信息的字符集
        resp.setCharacterEncoding("UTF-8");
        PrintWriter out= resp.getWriter();
        out.write("<html>");
        out.write("<head>");
        out.write("<meta charset=\"UTF-8\"");
        out.write("</head>");
        out.write("<body>");
        if("登陆成功".equals(result)){
            out.write("欢迎"+username+"进入ATM系统<br>");
            out.write("请输入操作选项<br>");
            out.write("<a href=\"query?username="+username+"\">查询</a><br>");
            out.write("<a href=\"query?username="+username+"\">存款</a><br>");
            out.write("<a href=\"query?username="+username+"\">取款</a><br>");
            out.write("<a href=\"query?username="+username+"\">转账</a><br>");
        }else{
            out.write(result);
        }
        out.write("</body>");
        out.write("</html>");
        out.flush();
    }
}

package controller;

import service.AtmService;
import util.MySpring;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class QueryController extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        String username=req.getParameter("username");
        AtmService atmService=MySpring.getJavaBean("service.AtmService");
        Float balance=atmService.inquire(username);

        resp.setCharacterEncoding("UTF-8");
        PrintWriter out= resp.getWriter();
        out.write("<html>");
        out.write("<head>");
        out.write("<meta charset=\"UTF-8\">");
        out.write("<script type=\"text/javascript\">" +
                "            window.onload=function () {" +
                "                var inputElement=document.getElementById(\"back\");" +
                "                inputElement.onclick=function () {" +
                "                    window.history.back();" +
                "                }" +
                "            }" +
                "        </script>");
        out.write("</head>");
        out.write("<body>");
        out.write("用户"+username+"您的余额为"+balance+"元<br>");
        out.write("<input id=\"back\" type=\"button\" value=\"返回\">");
        out.write("</body>");
        out.write("</html>");
        out.flush();
    }
}

package dao;

import domain.Atm;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class AtmDao {
    private String url="jdbc:mysql://localhost:3306/atm";
    private String className="com.mysql.jdbc.Driver";
    private String password="cy414ljh212,,,";

    public Atm selectOne(String username){
        Atm atm=null;
        try {
            Class.forName(className);
            Connection connection=DriverManager.getConnection(url,"root",password);
            String sql="SELECT USERNAME,PASSWORD,BALANCE FROM ATM WHERE USERNAME = ?";
            PreparedStatement preparedStatement=connection.prepareStatement(sql);
            preparedStatement.setString(1,username);
            ResultSet resultSet=preparedStatement.executeQuery();
            if(resultSet.next()){
                atm=new Atm();
                atm.setUsername(resultSet.getString("username"));
                atm.setPassword(resultSet.getString("password"));
                atm.setBalance(resultSet.getFloat("balance"));
            }
            resultSet.close();
            preparedStatement.close();
        }catch (Exception e){
            e.printStackTrace();
        }
        return atm;
    }
}

package domain;

public class Atm {
    private String username;
    private String password;
    private Float balance;

    public Atm(String username, String password, Float balance) {
        this.username = username;
        this.password = password;
        this.balance = balance;
    }

    public Atm() {
    }

    public String getUsername() {
        return username;
    }

    public String getPassword() {
        return password;
    }

    public Float getBalance() {
        return balance;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public void setBalance(Float balance) {
        this.balance = balance;
    }
}

package service;

import dao.AtmDao;
import domain.Atm;
import util.MySpring;

public class AtmService {
    private AtmDao atmDao= MySpring.getJavaBean("dao.AtmDao");

    public String login(String username,String password){
        String result="用户名或密码错误";
        Atm atm=atmDao.selectOne(username);
        if(atm!=null&&atm.getPassword().equals(password)){
            result="登陆成功";
        }
        return result;
    }

    public Float inquire(String username){
        return atmDao.selectOne(username).getBalance();
    }
}

package util;

import java.util.HashMap;

public class MySpring {
    private static HashMap<String,Object> beanMap=new HashMap<>();
    public static <T>T getJavaBean(String className){
        T obj=(T) beanMap.get(className);
        if(obj==null){
            try {
                    Class clazz=Class.forName(className);
                    obj=(T) clazz.newInstance();
                    beanMap.put(className,obj);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        return obj;
    }
}

<?xml version="1.0" encoding="GBK"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

<!--    登录-->
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>controller.LoginController</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

<!--    查询-->
    <servlet>
        <servlet-name>query</servlet-name>
        <servlet-class>controller.QueryController</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>query</servlet-name>
        <url-pattern>/query</url-pattern>
    </servlet-mapping>
</web-app>

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Title</title>
    </head>
    <body>
    <form action="login" method="post">
        <p>
            账号：<input type="text" name="username" value="请输入用户名" style="color: #999;"
                   onfocus="if(this.value =='请输入用户名'){this.value=''}">
        </p>
        <p>
            密码：<input type="password" name="password">
        </p>
        <input type="submit" value="登录">

    </form>
    </body>
</html>