前端与数据库交互

设计要求：

前端的HTML页面可以对数据库的一个数据表进行增删改查，并将结果以一个div的形式进行输出。

前端HTML页面（index.html）：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no" />
<title>Powered By Leisureeen</title>
<style>
table {
    border-collapse: collapse;
}

td {
    border: 1px solid #448844;
}
</style>
<script src="js/req.js"></script>
<script type="text/javascript">
    var mode = 0;
    function setVis(vis) {
        if (vis == 0)
            document.getElementById('name').style.visibility = "hidden";
        else
            document.getElementById('name').style.visibility = "visible";
    }
    function b_req() {
        var idV = document.getElementById("id").value;
        var nameV = document.getElementById("name").value;
        var result = document.getElementById("res");
        Request("db.do", "post", "mode=" + mode + "&id=" + idV + "&name="
                + nameV, result);
    }
</script>
</head>
<body bgcolor="CCDDFF">
    <div align="center" style="line-height: 30px;">
        Please Select a Mode:
        <br>
        <input type="radio" name="ra" onclick="mode=0;setVis(1)" checked="checked">
        增
        <input type="radio" name="ra" onclick="mode=1;setVis(0)">
        删
        <input type="radio" name="ra" onclick="mode=2;setVis(1)">
        改
        <input type="radio" name="ra" onclick="mode=3;setVis(1)">
        查
        <br>
        &nbsp;&nbsp;id:&nbsp;&nbsp;
        <input type="text" id="id" maxlength="11" value="18876543210">
        <br>
        name:
        <input type="text" id="name" maxlength="16" value="王炸">
        <br>
        <input type="submit" value="Submit" onclick="b_req()">
        <br>
        <div id="res" style="color: red"></div>
    </div>
</body>
</html>

req.js文件：

function Request(url, action, json, result) {
    var httpRequest = new XMLHttpRequest();
    httpRequest.open(action, url, true);
    httpRequest.setRequestHeader("Content-type",
            "application/x-www-form-urlencoded");
    httpRequest.send(json);
    httpRequest.onreadystatechange = function() {
        if (httpRequest.readyState == 4 && httpRequest.status == 200)
            result.innerHTML = httpRequest.responseText;
    };
}

web.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <display-name>html_db</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>database</servlet-name>
        <servlet-class>controller.Servlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>database</servlet-name>
        <url-pattern>/db.do</url-pattern>
    </servlet-mapping>
</web-app>

后端收发数据Java类（Servlet.java）：

package controller;

import java.io.IOException;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import math.*;

public class Servlet extends HttpServlet{

    protected void doPost(HttpServletRequest req,HttpServletResponse resp) throws ServletException, IOException{
        req.setCharacterEncoding("utf-8");// 这条语句竟然是我因为乱码然后自己摸索出来的，必须写上一行中文注释
        String mode=req.getParameter("mode");
        int modeI=Integer.parseInt(mode);
        String id=req.getParameter("id");
        String name=req.getParameter("name");
        resp.setContentType("application/json; charset=utf-8");
        if(modeI>3||modeI<0||name.length()>16)
            resp.getWriter().print("意外的错误。");
        else if(!(Str.isPhone(id)||modeI==3&&id.equals("")))
            resp.getWriter().print("id格式错误，应为11位手机号。");
        else if(modeI%2==0&&name.equals(""))
            resp.getWriter().print("请输入姓名！");
        else
            try{
                resp.getWriter().print(DB.dataIn(modeI,id,name));
            }catch(ClassNotFoundException e){
                // e.printStackTrace();
                resp.getWriter().print("ClassNotFoundException");
            }catch(SQLException e){
                // e.printStackTrace();
                resp.getWriter().print("SQLException");
            }
    }
}

后端字符串处理Java类（Str.java）：

package math;

public class Str{

    public static boolean isPhone(String s){
        if(s.length()!=11)
            return false;
        if(s.charAt(0)!='1')
            return false;
        for(int i=1;i<=10;i++)
            if(s.charAt(i)>'9'||s.charAt(i)<'0')
                return false;
        return true;
    }
}

后端数据库处理Java类（DB.java）：

package controller;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.mysql.jdbc.PreparedStatement;

public class DB{

    public static String dataIn(int mode,String id,String name) throws ClassNotFoundException, SQLException{
        int resN=0;
        String preStr="",outS="";
        Class.forName("com.mysql.jdbc.Driver");
        Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/html_db?characterEncoding=utf-8","root",
                "123456");
        if(mode==0){
            preStr="insert `maintable` values('"+id+"','"+name+"')";
            PreparedStatement ps=(PreparedStatement)con.prepareStatement(preStr);
            resN=ps.executeUpdate();
            outS+="操作成功，Inserted:"+id+"。";
            ps.close();
        }else if(mode==1){
            preStr="delete from `maintable` where `id`='"+id+"'";
            PreparedStatement ps=(PreparedStatement)con.prepareStatement(preStr);
            resN=ps.executeUpdate();
            outS+="操作成功，Deleted:"+id+"。";
            ps.close();
        }else if(mode==2){
            preStr="update `maintable` set `name`='"+name+"' where `id`='"+id+"'";
            PreparedStatement ps=(PreparedStatement)con.prepareStatement(preStr);
            resN=ps.executeUpdate();
            outS+="操作成功，Updated:"+id+"。";
            ps.close();
        }else{
            if(!id.equals(""))
                preStr="select * from `maintable` where `id`='"+id+"'";
            else if(!name.equals(""))
                preStr="select * from `maintable` where `name`='"+name+"'";
            else
                preStr="select * from `maintable`";
            PreparedStatement ps=(PreparedStatement)con.prepareStatement(preStr);
            ResultSet res=ps.executeQuery();
            outS+="<table>";
            for(resN=0;res.next();resN++)
                outS+="<tr><td>"+res.getString(1)+"</td><td>"+res.getString(2)+"</td></tr>";
            if(resN==0)
                outS+="<tr><td>无</td></tr>";
            outS+="</table>";
            outS="查询结果（共"+resN+"条记录）：<br>"+outS;
            res.close();
            ps.close();
        }
        con.close();
        return outS;
    }
}

数据库初始化文件（html_db.sql）：

CREATE DATABASE /*!32312 IF NOT EXISTS*/`html_db` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `html_db`;

/*Table structure for table `maintable` */

DROP TABLE IF EXISTS `maintable`;

CREATE TABLE `maintable` (
  `id` char(11) NOT NULL,
  `name` char(16) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 CHECKSUM=1 DELAY_KEY_WRITE=1 ROW_FORMAT=DYNAMIC;

前端与数据库交互

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