java web 就是对数据库的增删改查么

Posted 2023-03-15

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参考技术A 增删改查只是对数据的处理，java web是一类技术的总称，用java语言去实现和web相关的程序。参考技术B 这是一个form表单把数据发给后台的java action action中调用你操作数据库的dao或者是数据库的实现类实现类中有具体的增删改查,分页,模糊查询本回答被提问者采纳

jsp+servlet+jdbc实现对数据库的增删改查

一、JSP和Servlet的简单介绍

1、Servlet和JSP简介：

Java开发Web应用程序时用到的技术主要有两种，即Servlet和JSP，Servlet是在服务器端执行的Java程序，一个被称为Servlet容器的程序（其实就是服务器）负责执行Java程序，而JSP(Java Server Page)则是一个页面，由JSP容器负责执行.

2、Servlet和JSP的区别：

Servlet以Java程序为主，输出HTML代码时需要使用out.println函数，也就是说Java中内嵌HTML；而JSP则以HTML页面为主，需要写Java代码时则在页面中直接插入Java代码，即HTML中内嵌Java.

3、MVC模型

MVC模型就是将数据、逻辑处理、用户界面分离的一种方法
1）、M(Model, 模型)：用于数据处理、逻辑处理
2）、V(View，视图)：用于显示用户界面
3）、C(Controller，控制器)：根据客户端的请求控制逻辑走向和画面

而在Java中，MVC这三个部分则分别对应于 JavaBeans、JSP和Servlet
1）、M = JavaBeans：用于传递数据，拥有与数据相关的逻辑处理
2）、V = JSP：从Model接收数据并生成HTML
3）、C = Servlet：接收HTTP请求并控制Model和View

4、jdbc连接，可参考文章：点击打开链接

二、代码演示，实现了book的添加删除和修改功能

1、环境的配置

myeclipse+tomcat+mysql

2、Book中bean类

package example.bean.book;

public class Book {
	// 编号
	private int id;
	// 图书名称
	private String name;
	// 价格
	private double price;
	// 数量
	private int bookCount;
	// 作者
	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;
	}

}

3、Servlet类

1)、FindServlet.java

package example.servlet.book;

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
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 example.bean.book.Book;

/**
 * Servlet implementation class FindServlet
 */
public class FindServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		try {
			// 加载数据库驱动，注册到驱动管理器
			Class.forName("com.mysql.jdbc.Driver");
			// 数据库连接字符串
			String url = "jdbc:mysql://localhost:3306/db_book?useUnicode=true&characterEncoding=utf-8";
			// 数据库用户名
			String username = "root";
			// 数据库密码
			String password = "";
			// 创建Connection连接
			Connection conn = DriverManager.getConnection(url, username,
					password);
			// 添加图书信息的SQL语句
			String sql = "select * from tb_books";
			// 获取Statement
			Statement statement = conn.createStatement();

			ResultSet resultSet = statement.executeQuery(sql);

			List<Book> list = new ArrayList<Book>();
			while (resultSet.next()) {

				Book book = new Book();
				book.setId(resultSet.getInt("id"));
				book.setName(resultSet.getString("name"));
				book.setPrice(resultSet.getDouble("price"));
				book.setBookCount(resultSet.getInt("bookCount"));
				book.setAuthor(resultSet.getString("author"));
				list.add(book);

			}
			request.setAttribute("list", list);
			resultSet.close();
			statement.close();
			conn.close();

		} catch (Exception e) {
			e.printStackTrace();
		}

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

	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

2)、UpdateServlet.java类

package example.servlet.book;

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

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

/**
 * Servlet implementation class UpdateServlet
 */
public class UpdateServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		int id = Integer.valueOf(request.getParameter("id"));
		int bookCount = Integer.valueOf(request.getParameter("bookCount"));
		try {
			// 加载数据库驱动，注册到驱动管理器
			Class.forName("com.mysql.jdbc.Driver");
			// 数据库连接字符串
			String url = "jdbc:mysql://localhost:3306/db_book";
			// 数据库用户名
			String username = "root";
			// 数据库密码
			String password = "";
			// 创建Connection连接
			Connection conn = DriverManager.getConnection(url, username,
					password);
			// 更新SQL语句
			String sql = "update tb_books set bookcount=? where id=?";
			// 获取PreparedStatement
			PreparedStatement ps = conn.prepareStatement(sql);
			// 对SQL语句中的第一个参数赋值
			ps.setInt(1, bookCount);
			// 对SQL语句中的第二个参数赋值
			ps.setInt(2, id);
			// 执行更新操作
			ps.executeUpdate();
			// 关闭PreparedStatement
			ps.close();
			// 关闭Connection
			conn.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
		// 重定向到FindServlet
		response.sendRedirect("FindServlet");

	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

3）、DeleteServlet类

package example.servlet.book;

import java.io.IOException;
import java.sql.Connection;

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

import example.dao.book.BookJdbcDao;
import example.dao.book.ConnectionFactory;

/**
 * Servlet implementation class DeleteServlet
 */
public class DeleteServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		int id = Integer.valueOf(request.getParameter("id"));
		try {
//			// 加载数据库驱动，注册到驱动管理器
//			Class.forName("com.mysql.jdbc.Driver");
//			// 数据库连接字符串
//			String url = "jdbc:mysql://localhost:3306/db_book";
//			// 数据库用户名
//			String username = "root";
//			// 数据库密码
//			String password = "";
//			// 创建Connection连接
//			Connection conn = DriverManager.getConnection(url, username,
//					password);
//			// 删除图书信息的SQL语句
//			String sql = "delete from tb_books where id=?";
//			// 获取PreparedStatement
//			PreparedStatement ps = conn.prepareStatement(sql);
//			// 对SQL语句中的第一个占位符赋值
//			ps.setInt(1, id);
//			// 执行更新操作
//			ps.executeUpdate();
//			// 关闭PreparedStatement
//			ps.close();
//			// 关闭Connection
//			conn.close();
			BookJdbcDao bookDao=new BookJdbcDao();
			Connection conn=ConnectionFactory.getInstance().getConnection();
			bookDao.delete(conn,id);
			
		} catch (Exception e) {
			e.printStackTrace();
		}
		// 重定向到FindServlet
		response.sendRedirect("FindServlet");
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}

}

4、servlet访问url映射配置：

由于客户端是通过URL地址访问web服务器中的资源，所以Servlet程序若想被外界访问，必须把servlet程序映射到一个URL地址上，这个工作在web.xml文件中使用<servlet>元素和<servlet-mapping>元素完成，<servlet>元素用于注册Servlet，它包含有两个主要的子元素：<servlet-name>和<servlet-class>，分别用于设置Servlet的注册名称和Servlet的完整类名。一个<servlet-mapping>元素用于映射一个已注册的Servlet的一个对外访问路径，它包含有两个子元素：<servlet-name>和<url-pattern>，分别用于指定Servlet的注册名称和Servlet的对外访问路径.另外：同一个Servlet可以被映射到多个URL上，即多个<servlet-mapping>元素的<servlet-name>子元素的设置值可以是同一个Servlet的注册名.

eg:上例中的web.xml

<?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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>JdbcConnection</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>
    <description></description>
    <display-name>FindServlet</display-name>
    <servlet-name>FindServlet</servlet-name>
    <servlet-class>example.servlet.book.FindServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>FindServlet</servlet-name>
    <url-pattern>/FindServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>UpdateServlet</display-name>
    <servlet-name>UpdateServlet</servlet-name>
    <servlet-class>example.servlet.book.UpdateServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>UpdateServlet</servlet-name>
    <url-pattern>/UpdateServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>DeleteServlet</display-name>
    <servlet-name>DeleteServlet</servlet-name>
    <servlet-class>example.servlet.book.DeleteServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>DeleteServlet</servlet-name>
    <url-pattern>/DeleteServlet</url-pattern>
  </servlet-mapping>
</web-app>

5、jsp页面

1）、index.jsp web页面主界面

<%@page import="java.sql.SQLException"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.Connection"%>
<%@ 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>添加图书信息</title>

<script type="text/javascript">
	function check(form) {
		with (form) {
			if (name.value == "") {
				alert("图书名称不能为空");
				return false;
			}

			if (price.value == "") {
				alert("图书价格不能为空");
				return false;
			}

			if (author.value == "") {
				alert("作者不能为空");
				return false;
			}

		}
	}
</script>

</head>


<body>

<form action="addbook.jsp" method="post" οnsubmit="check(this)">
	<table align="center" width="450">
		<tr>
			<td align="center" colspan="2">
				<h2>添加图书信息</h2>
				<hr>
			</td>
		</tr>

		<tr>
			<td align="right">图书名称：</td>
			<td><input type="text" name="name"></td>
		</tr>

		<tr>
			<td align="right">价 格：</td>
			<td><input type="text" name="price"></td>
		</tr>

		<tr>
			<td align="right">数 量：</td>
			<td><input type="text" name="bookCount" /></td>
		</tr>

		<tr>
			<td align="right">作 者：</td>
			<td><input type="text" name="author" /></td>
		</tr>
		<tr>
			<td align="center" colspan="2"><input type="submit" value="添　加">
			</td>
		</tr>
	</table>
</form>

<h2 align="center">
	<a href="FindServlet">查询图书信息</a>
</h2>

</body>
</html>

2)、addbook.jsp 添加书籍成功或者失败后的显示页面

<%@ 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">

<%@page import="java.sql.Connection"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.PreparedStatement"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>添加结果</title>
</head>
<body>
	<%
		request.setCharacterEncoding("utf-8");
	%>
	<jsp:useBean id="book" class="example.bean.book.Book"></jsp:useBean>
	<jsp:setProperty property="*" name="book" />
	<%
		try {
			// 加载数据库驱动，注册到驱动管理器
			Class.forName("com.mysql.jdbc.Driver");
			// 数据库连接字符串
			String url = "jdbc:mysql://localhost:3306/db_book?useUnicode=true&characterEncoding=utf-8";
			// 数据库用户名
			String username = "root";
			// 数据库密码
			String password = "";
			// 创建Connection连接
			Connection conn = DriverManager.getConnection(url, username,
					password);
			// 添加图书信息的SQL语句
			String sql = "insert into tb_books(name,price,bookCount,author) values(?,?,?,?)";
			// 获取PreparedStatement
			PreparedStatement ps = conn.prepareStatement(sql);
			// 对SQL语句中的第1个参数赋值
			ps.setString(1, book.getName());
			// 对SQL语句中的第2个参数赋值
			ps.setDouble(2, book.getPrice());
			// 对SQL语句中的第3个参数赋值
			ps.setInt(3, book.getBookCount());
			// 对SQL语句中的第4个参数赋值
			ps.setString(4, book.getAuthor());
			// 执行更新操作，返回所影响的行数
			int row = ps.executeUpdate();
			// 判断是否更新成功
			if (row > 0) {
				// 更新成输出信息
				out.print("成功添加了 " + row + "条数据！");
			}
			// 关闭PreparedStatement，释放资源
			ps.close();
			// 关闭Connection，释放资源
			conn.close();
		} catch (Exception e) {
			out.print("图书信息添加失败！");
			e.printStackTrace();
		}
	%>
	<br>
	<a href="index.jsp">返回</a>
</body>
</html>

3)、book_list.jsp 查找所有书籍信息的显示页面，以表格方式显示

<!--<%@page import="sun.awt.SunHints.Value"%>-->
<%@ 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">

<%@page import="java.util.List"%>
<%@page import="example.bean.book.Book"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>所有图书信息</title>
<style type="text/css">
td {
	font-size: 12px;
}

h2 {
	margin: 0px
}
</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>
	<table align="center" width="450" border="1" height="180"
		bordercolor="white" bgcolor="black" cellpadding="1" cellspacing="1">
		<tr bgcolor="white">
			<td align="center" colspan="7">
				<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</b></td>
			<td><b>删除</b></td>
		</tr>
		<%
			// 获取图书信息集合
			List<Book> list = (List<Book>) request.getAttribute("list");
			// 判断集合是否有效
			if (list == null || 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>
			<td >
				<form style="align:center;  background-color: gray" action="UpdateServlet" method="post"
					οnsubmit="return check(this);">
					 <input type="hidden" name="id" value="<%=book.getId()%>"> <input
						type="text" name="bookCount" size="3">
				     <input type="submit" value="修改数量">
				</form>
			</td>
		    <td>
		    <a href="DeleteServlet?id=<%=book.getId()%>">删除</a>
		    </td>


		</tr>
		<%
			}
			}
		%>
	</table>
	<h2 align="center">
		<a href="index.jsp">返回添加图书信息页面</a>
	</h2>

</body>
</html>

6、jdbc简单的封装

1）、ConnectionFactory.java工厂类

package example.dao.book;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConnectionFactory {
	
	private String driverClassName = "com.mysql.jdbc.Driver";
	private String url = "jdbc:mysql://localhost:3306/db_book?useUnicode=true&characterEncoding=utf-8";
	private String userName = "root";
	private String password = "";
	
	private static ConnectionFactory connectionFactory=null;

	private ConnectionFactory() {
		
		try {
			Class.forName(driverClassName);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	
	public  Connection getConnection() throws SQLException
	{
		return DriverManager.getConnection(url, userName, password);
		
	}
	
	public static ConnectionFactory getInstance()
	{   
		if (null==connectionFactory) {
			connectionFactory=new ConnectionFactory();
		}
		return connectionFactory;
		
	}
	
	

}

2）、BookJdbcDao.java数据库操作封装类

package example.dao.book;

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

import example.bean.book.Book;

public class BookJdbcDao {
	
	private PreparedStatement ptmt = null;
	private ResultSet rs = null;

	public BookJdbcDao() {
	}
	
	
	public void findAll(Connection conn) throws SQLException
	{
		//to do
		
	}
	
	public void delete(Connection conn, int id) throws SQLException
	{
		String sql = "delete from tb_books where id=?";
		try{
			ptmt = conn.prepareStatement(sql);
			// 对SQL语句中的第一个占位符赋值
			ptmt.setInt(1, id);
			// 执行更新操作
			ptmt.executeUpdate();
			
		}finally{
			if (null!=ptmt) {
				ptmt.close();
			}
			
			if (null!=conn) {
				conn.close();
			}
			
		}
		
	}
	
	public void update(Connection conn, int id ,int bookcount) throws SQLException
	{
		//to do
		
	}
	

}

源代码下载链接

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