JSP 创建 CRUD 示例 DAO 用于数据库JSTL 用于遍历记录

编程语言 2023-10-05 05:45:11 阅读次数: 0

在本 Java 教程中，我们将帮助您了解编写基本 Java Web 应用程序的过程，该应用程序管理具有基本功能的用户集合：列表、插入、更新、删除（或 CURD 操作 - 创建、更新、读取和删除）。该应用程序看起来像这样：

您将学习如何使用以下技术构建此应用程序：

  • Java 服务器页面 (JSP)
  • JSP 标准标签库 (JSTL)
  • Java 数据库连接 (JDBC)
  • MySQL数据库
  • Apache Tomcat 服务器

我们使用 Eclipse IDE 和 Maven 来开发项目。

1. 创建 MySQL 数据库

为简单起见，我们只有一张桌子。执行以下 MySQL 脚本以创建名为test的数据库和名为register的表：

CREATE DATABASE `test`;

CREATE TABLE IF NOT EXISTS `user` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `name` varchar(100) NOT NULL,
  `password` varchar(100) NOT NULL,
  `email` varchar(100) NOT NULL,
  `sex` varchar(100) NOT NULL,
  `country` varchar(100) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB   ;

INSERT INTO `user` (`id`, `name`, `password`, `email`, `sex`, `country`) VALUES
(17, 'arun', 'kumar', '[email protected]', 'Male', 'India'),
(19, 'sonoo', 'jaiswal', '[email protected]', 'male', 'India'),
(20, 'Ashok', 'ashok', '[email protected]', 'male', 'India');

您可以使用 MySQL 命令行客户端或 MySQL Workbench 工具来创建数据库。

2. 使用 Maven 创建 Eclipse 项目

在 Eclipse IDE 中，单击File > New > Dynamic Web Project以创建一个新的 Java 动态 Web 项目。将项目命名为UserReg：

请记住将Target runtime选择为Apache Tomcat v8.0，将Dynamic web module version选择为3.1（这是 Java servlet 版本）。

单击完成。然后将此项目转换为 Maven 项目，右键项目，选择Configure > Convert to Maven Project，如下图：

创建 Maven POM 文件需要输入信息，例如组 ID、工件 ID 等。然后在pom.xml 文件中添加以下依赖项：

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>UserReg</groupId>
	<artifactId>UserReg</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
	<dependencies>
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.1.0</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>javax.servlet.jsp-api</artifactId>
			<version>2.3.1</version>
			<scope>provided</scope>
		</dependency>
		<dependency>
			<groupId>jstl</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>8.0.28</version>
		</dependency>
	</dependencies>
	<build>
		<sourceDirectory>src</sourceDirectory>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.8.1</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
			<plugin>
				<artifactId>maven-war-plugin</artifactId>
				<version>3.2.3</version>
				<configuration>
					<warSourceDirectory>WebContent</warSourceDirectory>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

如您所见，这里的依赖项是针对 Servlet、JSP、JSTL 和 MySQL 连接器 Java（MySQL 的 JDBC 驱动程序）。

3. 编写模型类

接下来，使用以下代码创建一个名为User.java的 Java 类来对数据库中的User实体进行建模：

package com.javatpoint.bean;

public class User {
	private int id;
	private String name, password, email, sex, country;

	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 String getPassword() {
		return password;
	}

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

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public String getCountry() {
		return country;
	}

	public void setCountry(String country) {
		this.country = country;
	}

}

如您所见，该类根据数据库中表book中的 6列有 6个字段：id、name、password, email, sex和  country。

4.编码DAO类

接下来，我们需要实现一个数据访问层 (DAO) 类，该类为数据库中的表user提供 CRUD（创建、读取、更新、删除）操作。这是UserDAO类的完整源代码：

package com.javatpoint.dao;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

import com.javatpoint.bean.User;

public class UserDao {
	public static Connection getConnection() {
		Connection con = null;
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
			con = DriverManager.getConnection(
					"jdbc:mysql://localhost:3306/test?autoReconnect=true&useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai",
					"root", "root");
		} catch (Exception e) {
			System.out.println(e);
		}
		return con;
	}

	public static int save(User u) {
		int status = 0;
		try {
			Connection con = getConnection();
			PreparedStatement ps = con
					.prepareStatement("insert into user(name,password,email,sex,country) values(?,?,?,?,?)");
			ps.setString(1, u.getName());
			ps.setString(2, u.getPassword());
			ps.setString(3, u.getEmail());
			ps.setString(4, u.getSex());
			ps.setString(5, u.getCountry());
			status = ps.executeUpdate();
		} catch (Exception e) {
			System.out.println(e);
		}
		return status;
	}

	public static int update(User u) {
		int status = 0;
		try {
			Connection con = getConnection();
			PreparedStatement ps = con
					.prepareStatement("update user set name=?,password=?,email=?,sex=?,country=? where id=?");
			ps.setString(1, u.getName());
			ps.setString(2, u.getPassword());
			ps.setString(3, u.getEmail());
			ps.setString(4, u.getSex());
			ps.setString(5, u.getCountry());
			ps.setInt(6, u.getId());
			status = ps.executeUpdate();
		} catch (Exception e) {
			System.out.println(e);
		}
		return status;
	}

	public static int delete(User u) {
		int status = 0;
		try {
			Connection con = getConnection();
			PreparedStatement ps = con.prepareStatement("delete from user where id=?");
			ps.setInt(1, u.getId());
			status = ps.executeUpdate();
		} catch (Exception e) {
			System.out.println(e);
		}

		return status;
	}

	public static List<User> getAllRecords() {
		List<User> list = new ArrayList<User>();

		try {
			Connection con = getConnection();
			PreparedStatement ps = con.prepareStatement("select * from user");
			ResultSet rs = ps.executeQuery();
			while (rs.next()) {
				User u = new User();
				u.setId(rs.getInt("id"));
				u.setName(rs.getString("name"));
				u.setPassword(rs.getString("password"));
				u.setEmail(rs.getString("email"));
				u.setSex(rs.getString("sex"));
				u.setCountry(rs.getString("country"));
				list.add(u);
			}
		} catch (Exception e) {
			System.out.println(e);
		}
		return list;
	}

	public static User getRecordById(int id) {
		User u = null;
		try {
			Connection con = getConnection();
			PreparedStatement ps = con.prepareStatement("select * from user where id=?");
			ps.setInt(1, id);
			ResultSet rs = ps.executeQuery();
			while (rs.next()) {
				u = new User();
				u.setId(rs.getInt("id"));
				u.setName(rs.getString("name"));
				u.setPassword(rs.getString("password"));
				u.setEmail(rs.getString("email"));
				u.setSex(rs.getString("sex"));
				u.setCountry(rs.getString("country"));
			}
		} catch (Exception e) {
			System.out.println(e);
		}
		return u;
	}
}

如您所见，JDBC 连接信息是通过其构造函数注入到此类的。以下方法适用于 CRUD 操作：

5.编写JSP页面

接下来，创建 JSP 页面来显示数据库中的所有书籍。以下是项目中WebContent目录下jsp页面的代码：

index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<!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=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>

	<a href="adduserform.jsp">Add User</a>
	<a href="viewusers.jsp">View Users</a>

</body>
</html>

adduserform.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Add User Form</title>
</head>
<body>

	<jsp:include page="userform.html"></jsp:include>

</body>
</html>

userform.html

<a href="viewusers.jsp">View All Records</a>
<br />

<h1>Add New User</h1>
<form action="adduser.jsp" method="post">
	<table>
		<tr>
			<td>Name:</td>
			<td><input type="text" name="name" /></td>
		</tr>
		<tr>
			<td>Password:</td>
			<td><input type="password" name="password" /></td>
		</tr>
		<tr>
			<td>Email:</td>
			<td><input type="email" name="email" /></td>
		</tr>
		<tr>
			<td>Sex:</td>
			<td><input type="radio" name="sex" value="male" />Male <input
				type="radio" name="sex" value="female" />Female</td>
		</tr>
		<tr>
			<td>Country:</td>
			<td><select name="country" style="width: 155px">
					<option>India</option>
					<option>Pakistan</option>
					<option>Afghanistan</option>
					<option>Berma</option>
					<option>Other</option>
			</select></td>
		</tr>
		<tr>
			<td colspan="2"><input type="submit" value="Add User" /></td>
		</tr>
	</table>
</form>
adduser.jsp 
<%@page import="com.javatpoint.dao.UserDao"%>
<jsp:useBean id="u" class="com.javatpoint.bean.User"></jsp:useBean>
<jsp:setProperty property="*" name="u" />

<%
	int i = UserDao.save(u);
if (i > 0) {
	response.sendRedirect("adduser-success.jsp");
} else {
	response.sendRedirect("adduser-error.jsp");
}
%>

adduser-success.jsp

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Add User Success</title>
</head>
<body>

	<p>Record successfully saved!</p>
	<jsp:include page="userform.html"></jsp:include>

</body>
</html>

adduser-error.jsp

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Add User Success</title>
</head>
<body>

	<p>Sorry, an error occured!</p>
	<jsp:include page="userform.html"></jsp:include>

</body>
</html>

viewusers.jsp

<!DOCTYPE html>

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>View Users</title>
</head>
<body>

	<%@page
		import="com.javatpoint.dao.UserDao,com.javatpoint.bean.*,java.util.*"%>
	<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

	<h1>Users List</h1>

	<%
		List<User> list = UserDao.getAllRecords();
	request.setAttribute("list", list);
	%>

	<table border="1" width="90%">
		<tr>
			<th>Id</th>
			<th>Name</th>
			<th>Password</th>
			<th>Email</th>
			<th>Sex</th>
			<th>Country</th>
			<th>Edit</th>
			<th>Delete</th>
		</tr>
		<c:forEach items="${list}" var="u">
			<tr>
				<td>${u.getId()}</td>
				<td>${u.getName()}</td>
				<td>${u.getPassword()}</td>
				<td>${u.getEmail()}</td>
				<td>${u.getSex()}</td>
				<td>${u.getCountry()}</td>
				<td><a href="editform.jsp?id=${u.getId()}">Edit</a></td>
				<td><a href="deleteuser.jsp?id=${u.getId()}">Delete</a></td>
			</tr>
		</c:forEach>
	</table>
	<br />
	<a href="adduserform.jsp">Add New User</a>

</body>
</html>

editform.jsp

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Edit Form</title>
</head>
<body>
	<%@page import="com.javatpoint.dao.UserDao,com.javatpoint.bean.User"%>

	<%
		String id = request.getParameter("id");
	User u = UserDao.getRecordById(Integer.parseInt(id));
	%>

	<h1>Edit Form</h1>
	<form action="edituser.jsp" method="post">
		<input type="hidden" name="id" value="<%=u.getId()%>" />
		<table>
			<tr>
				<td>Name:</td>
				<td><input type="text" name="name" value="<%=u.getName()%>" /></td>
			</tr>
			<tr>
				<td>Password:</td>
				<td><input type="password" name="password"
					value="<%=u.getPassword()%>" /></td>
			</tr>
			<tr>
				<td>Email:</td>
				<td><input type="email" name="email" value="<%=u.getEmail()%>" /></td>
			</tr>
			<tr>
				<td>Sex:</td>
				<td><input type="radio" name="sex" value="male" />Male <input
					type="radio" name="sex" value="female" />Female</td>
			</tr>
			<tr>
				<td>Country:</td>
				<td><select name="country">
						<option>India</option>
						<option>Pakistan</option>
						<option>Afghanistan</option>
						<option>Berma</option>
						<option>Other</option>
				</select></td>
			</tr>
			<tr>
				<td colspan="2"><input type="submit" value="Edit User" /></td>
			</tr>
		</table>
	</form>

</body>
</html>

edituser.jsp

<%@page import="com.javatpoint.dao.UserDao"%>
<jsp:useBean id="u" class="com.javatpoint.bean.User"></jsp:useBean>
<jsp:setProperty property="*" name="u" />

<%
	int i = UserDao.update(u);
response.sendRedirect("viewusers.jsp");
%>

deleteuser.jsp

<%@page import="com.javatpoint.dao.UserDao"%>
<jsp:useBean id="u" class="com.javatpoint.bean.User"></jsp:useBean>
<jsp:setProperty property="*" name="u" />

<%
	UserDao.delete(u);
response.sendRedirect("viewusers.jsp");
%>

6. 部署和测试应用程序

至此我们已经完成了项目的代码。是时候部署和测试应用程序以了解它是如何工作的了。如果您不知道如何在 Eclipse 中添加 Apache Tomcat 服务器，请遵循本教程。

在 Web 浏览器中键入以下 URL 以访问 UserReg应用程序：

http://localhost:8080/UserReg

输出

      

下载项目

在 JSP 中下载 CRUD 项目

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