JavaWeb——操作数据库之JDBC查询和更新数据

其他 2020-02-08 18:31:30 阅读次数: 0

JavaWeb——JDBC 操作数据库

四、JDBC 向 MySQL 数据库查询和更新数据

1、查询数据

  • 新建一个 JSP 页面，编辑如下代码：
    <%--
Created by IntelliJ IDEA.
User: 御承扬
Date: 2019/12/2
Time: 16:43
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="java.util.List" %>
<%@page import="com.lyq.bean.Book" %>
<%@ page import="java.sql.*" %>
<%@ page import="java.util.ArrayList" %>
<html>
<head>
    <title>图书信息查询结果页面</title>
    <style type="text/css">
        body {
            background: #d7c7e9;
            align-items: center;
            text-align: center;
        }
    </style>
</head>
<body>
<table align="center" width="450" border="1" height="180" bordercolor="white" bgcolor="black" cellpadding="1"
       cellspacing="1">
    <tr bgcolor="white">
        <td align="center" colspan="5">
            <h2>所有图书信息</h2>
        </td>
    </tr>
    <tr align="center" bgcolor="#e1ffc1">
        <td><b>ID</b></td>
        <td><b>图书名称</b></td>
        <td><b>价格</b></td>
        <td><b>数量</b></td>
        <td><b>作者</b></td>
    </tr>
    <%
        // 获取图书信息集合
        //List<Book> list = (List<Book>) request.getAttribute("list");
        try {
                Class.forName("com.mysql.jdbc.Driver");
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
            String url = "jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8";
            String username = "root";
            String password = "**********";
            Connection conn = null;
            Statement stmt =null;
            ResultSet rs = null;
            List<Book> list = new ArrayList<Book>();
            try {
                conn = DriverManager.getConnection(url, username, password);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            if(conn != null){
                try{
                    stmt = conn.createStatement();
                    String sql = "select * from tb_books;";
                    rs = stmt.executeQuery(sql);

                    while (rs.next()) {
                        Book book = new Book();
                        book.setId(rs.getInt("id"));
                        book.setName(rs.getString("name"));
                        book.setPrice(rs.getDouble("price"));
                        book.setBookCount(rs.getInt("bookCount"));
                        book.setAuthor(rs.getString("author"));
                        list.add(book);
                    }
                }catch(SQLException e){
                        e.printStackTrace();
                        out.print("查询失败！");
                    }
            }
        // 判断集合是否有效
        if (list.size() < 1) {
            out.print("没有数据！");
        } else {
            // 遍历图书集合中的数据
            for (Book book : list) {
    %>
    <tr align="center" bgcolor="white">
        <td><%=book.getId()%>
        </td>
        <td><%=book.getName()%>
        </td>
        <td><%=book.getPrice()%>
        </td>
        <td><%=book.getBookCount()%>
        </td>
        <td><%=book.getAuthor()%>
        </td>
    </tr>
    <%
            }
            try {
                rs.close();
                stmt.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }

    }
    %>
    <tr bgcolor="white">
    <td align="center" colspan="5">
        <input type="button" value="添加图书信息" onclick="window.location.href='book.jsp'">
    </td>
</table>
</body>
</html>
  • 效果如下：
    在这里插入图片描述

2、更新数据

  • 更新数据稍微麻烦点，首先新建两个 Servlet 。
  • 第一个 Servlet：
    //@Software: IntelliJ IDEA
// @Project: JavaWebProject1
//@File:${NAME}
//@Date:2019/12/3
// Author:御承扬
//E-mail:[email protected]
package com.lyq.ServletSet;
import com.lyq.bean.Book;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
@WebServlet(name = "FindServlet", urlPatterns = "/FindServlet")
public class FindServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        String url = "jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8";
        String username = "root";
        String password = "*********";
        Connection conn = null;
        Statement stmt =null;
        ResultSet rs = null;
        List<Book> list = new ArrayList<>();
        try {
            conn = DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        if(conn != null){
            try{
                stmt = conn.createStatement();
                String sql = "select * from tb_books;";
                rs = stmt.executeQuery(sql);

                while (rs.next()) {
                    Book book = new Book();
                    book.setId(rs.getInt("id"));
                    book.setName(rs.getString("name"));
                    book.setPrice(rs.getDouble("price"));
                    book.setBookCount(rs.getInt("bookCount"));
                    book.setAuthor(rs.getString("author"));
                    list.add(book);
                }
                request.setAttribute("list", list);
                rs.close();
                stmt.close();
                conn.close();
            }catch(SQLException e){
                e.printStackTrace();
            }
        }
        request.getRequestDispatcher("/JDBCOption/bookUpdate.jsp").forward(request, response);
    }
}
  • 第二个 Servlet
    //@Software: IntelliJ IDEA
// @Project: JavaWebProject1
//@File:${NAME}
//@Date:2019/12/3
// Author:御承扬
//E-mail:[email protected]
package com.lyq.ServletSet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

@WebServlet(name = "UpdateServlet", urlPatterns = "/UpdateServlet")
public class UpdateServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        int bookCount = Integer.parseInt(request.getParameter("bookCount"));
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        String url = "jdbc:mysql://localhost:3306/test?serverTimezone=GMT%2B8";
        String username = "root";
        String password = "**********";
        Connection conn = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        if(conn != null){
            String sql = "update tb_books set bookCount=? where id=?";
            try {
                PreparedStatement ps = conn.prepareStatement(sql);
                ps.setInt(2,id);
                ps.setInt(1, bookCount);
                ps.executeUpdate();
                ps.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            response.sendRedirect("FindServlet");
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}
  • 在建立一个 JSP 页面，代码如下：
    <%--
Created by IntelliJ IDEA.
User: 御承扬
Date: 2019/12/3
Time: 14:47
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="com.lyq.bean.Book"%>
<%@ page import="java.sql.*" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<html>
<head>
    <title>修改图书信息</title>
    <style type="text/css">
        body{
            background: #d7c7e9;
            align-items: center;
            text-align: center;
        }
    </style>
    <script type="text/javascript">
        function check(form){
            with(form){
                if(bookCount.value === ""){
                    alert("图书数量不能为空");
                    return false;
                }
                return true;
            }
        }
    </script>
</head>
<body>
<table align="center" width="450" border="1" height="180" bordercolor="white" cellpadding="1"
       cellspacing="1">
    <tr bgcolor="white">
        <td align="center" colspan="6">
            <h2>所有图书信息</h2>
        </td>
    </tr>
    <tr align="center" bgcolor="#e1ffc1">
        <td><b>ID</b></td>
        <td><b>图书名称</b></td>
        <td><b>价格</b></td>
        <td><b>数量</b></td>
        <td><b>作者</b></td>
        <td><b>修改数量</b></td>
    </tr>
    <%
        List<Book> list = (List<Book>) request.getAttribute("list");
        if(list == null ||list.size() < 1){
            out.print("没有数据");
        }else{
            for(Book book:list){


    %>
        <tr align="center">
            <td><%=book.getId()%>
            </td>
            <td><%=book.getName()%>
            </td>
            <td><%=book.getPrice()%>
            </td>
            <td><%=book.getBookCount()%>
            </td>
            <td><%=book.getAuthor()%>
            </td>
            <td>
                <form action="${pageContext.request.contextPath}/UpdateServlet" method="post" onsubmit="return check(this)">
                    <input type="hidden" name="id" value="<%=book.getId()%>">
                    <label>
                        <input type="text" name="bookCount" size="3">
                    </label>
                    <input type="submit" value="修改">
                </form>
            </td>
        </tr>
    <%
            }
        }
    %>
    <tr bgcolor="white">
        <td align="center" colspan="6">
            <input type="button" value="添加图书信息" onclick="window.location.href='book.jsp'">
        </td>
</table>
</body>
</html>
  • 运行效果如下：
    在这里插入图片描述
  • 对第三行的数量进行修改
    在这里插入图片描述
  • 点击修改
    在这里插入图片描述

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