JDBC操作数据库之删除数据

删除数据使用的SQL语句为delete语句，如果删除图书id为1的图书信息，其SQL语句为：

delete from book where id=1

在实际开发中删除数据通常使用PreparedStatement对象进行操作。

实例代码：

（1）index.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 <title>查看所有图书</title>
 </head>
 <body>
     <a href="FindServlet">查看所有图书</a>
 </body>
 </html>

（2）book_list.jsp

 <%@ page language="java" contentType="text/html; charset=UTF-8"
     pageEncoding="UTF-8"%>
 <%@ page import="com.java.Book" %>
 <%@ page import="java.util.ArrayList" %>
 <%@ page import="java.util.List" %>
 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 <html>
 <head>
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 <title>删除数据</title>
 <style>
     td{
         font-size:12px;
     }
     h2{
         margin:2px;
     }
 </style>
 <script type="text/javascript">
     function check(form){
         with(form){
             if(bookCount.value == ""){
                 alert("请输入更新数量！");
                 return false;
             }
             if(isNaN(bookCount.value)){
                 alert("格式错误！");
                 return false;
             }
             return true;
         }
     }
 </script>
 </head>
 <body>
     <div style="text-align:center;">
         <table align="center" width="500px" border="1" height="170px" bordercolor="white" bgcolor="black" cellpadding="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>作者</b></td>
                 <td><b>修改数量</b></td>
                 <td><b>删除</b></td>
             </tr>
             <%
                 List<Book> list = (List<Book>)request.getAttribute("list");
                 if(list ==null || list.size() < 1){
                     out.print("数据为空");
                 }else{
                     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>
                 <td>
                     <a href="DeleteServlet?id=<%=book.getId()%>">删除</a>
                 </td>
             </tr>
             <%
                     }
                 }
             %>
          </table>
     </div>
 </body>
 </html>

查看代码

（3）Book类

 package com.java;

 public class Book {
      private int id;
         private String name;
         private double price;
         private int bookCount;
         private String author;
         public int getId() {
             return id;
         }
         public void setId(int id) {
             this.id = id;
         }
         public String getName() {
             return name;
         }
         public void setName(String name) {
             this.name = name;
         }
         public double getPrice() {
             return price;
         }
         public void setPrice(double price) {
             this.price = price;
         }
         public int getBookCount() {
             return bookCount;
         }
         public void setBookCount(int bookCount) {
             this.bookCount = bookCount;
         }
         public String getAuthor() {
             return author;
         }
         public void setAuthor(String author) {
             this.author = author;
         }
 }

查看代码

（4）FindServlet类

 package com.java;

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

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

 import com.java.Book;

 public class FindServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;
     private String sql = "select * from book";
     private String url = "jdbc:mysql://localhost:3306/test";
     private String username = "root";
     private String password = "123456";

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         try {
             Class.forName("com.mysql.jdbc.Driver");
         } catch (ClassNotFoundException e1) {
             // TODO Auto-generated catch block
             e1.printStackTrace();
         }
         Connection conn=null;
         try {
             conn = DriverManager.getConnection(url,username,password);
         } catch (SQLException e1) {
             // TODO Auto-generated catch block
             e1.printStackTrace();
         }

         try {
             PreparedStatement ps = conn.prepareStatement(sql);
             ResultSet rs = ps.executeQuery(sql);
             List<Book> list = (List<Book>)new ArrayList();
             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();
             ps.close();
             conn.close();
         } catch (SQLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }

         request.getRequestDispatcher("book_list.jsp").forward(request, response);
     }
 }

查看代码

（5）DeleteServlet类

 package com.java;

 import java.io.IOException;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.SQLException;

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

 public class DeleteServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;
     protected void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException{
         int id = Integer.valueOf(request.getParameter("id"));

             try {
                 Class.forName("com.mysql.jdbc.Driver");
                 String url = "jdbc:mysql://localhost:3306/test";
                 String username = "root";
                 String password = "123456";
                 Connection conn=null;
                 try {
                     conn = DriverManager.getConnection(url,username,password);
                 } catch (SQLException e1) {
                     // TODO Auto-generated catch block
                     e1.printStackTrace();
                 }
                 String sql = "delete from book where id=?";
                 PreparedStatement ps;
                 try {
                     ps = conn.prepareStatement(sql);
                     ps.setInt(1, id);
                     ps.executeUpdate();
                     ps.close();
                     conn.close();
                 } catch (SQLException e) {
                     // TODO Auto-generated catch block
                     e.printStackTrace();
                 }

             } catch (ClassNotFoundException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }

             response.sendRedirect("FindServlet");

     }

 }

查看代码

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