JSP 实现数据的增删改操作实践
JavaServer Pages（JSP）是一种动态网页技术，它允许开发者使用Java代码来生成HTML页面。JSP技术结合了Java的强类型语言特性和HTML的易用性，使得开发动态网页变得更加高效。本文将围绕JSP实现数据的增删改操作进行实践，通过一系列的示例代码，展示如何使用JSP和JavaBean来管理数据库中的数据。
环境准备
在开始实践之前，我们需要准备以下环境：
1. Java Development Kit（JDK）：推荐使用JDK 8或更高版本。
2. Java EE Web服务器：如Apache Tomcat。
3. 数据库：如MySQL、Oracle等。
数据库设计
为了演示增删改操作，我们假设有一个简单的用户表（users）：
sql
CREATE TABLE users (
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(50) NOT NULL,
password VARCHAR(50) NOT NULL,
email VARCHAR(100)
);
创建JavaBean
我们需要创建一个JavaBean来表示用户表中的数据。这个JavaBean将包含用户的所有属性以及相应的getter和setter方法。
java
public class User {
private int id;
private String username;
private String password;
private String email;
// Getter 和 Setter 方法
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
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;
}
}
创建数据访问对象（DAO）
接下来，我们需要创建一个数据访问对象（DAO）来处理与数据库的交互。这个对象将包含增删改查（CRUD）操作的方法。
java
import java.sql.;
import java.util.ArrayList;
import java.util.List;
public class UserDAO {
private Connection getConnection() throws SQLException {
String url = "jdbc:mysql://localhost:3306/your_database";
String user = "your_username";
String password = "your_password";
return DriverManager.getConnection(url, user, password);
}
public List<User> getAllUsers() {
List<User> users = new ArrayList<>();
String sql = "SELECT FROM users";
try (Connection conn = getConnection();
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql)) {
while (rs.next()) {
User user = new User();
user.setId(rs.getInt("id"));
user.setUsername(rs.getString("username"));
user.setPassword(rs.getString("password"));
user.setEmail(rs.getString("email"));
users.add(user);
}
} catch (SQLException e) {
e.printStackTrace();
}
return users;
}
public void addUser(User user) {
String sql = "INSERT INTO users (username, password, email) VALUES (?, ?, ?)";
try (Connection conn = getConnection();
PreparedStatement pstmt = conn.prepareStatement(sql)) {
pstmt.setString(1, user.getUsername());
pstmt.setString(2, user.getPassword());
pstmt.setString(3, user.getEmail());
pstmt.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
}
public void updateUser(User user) {
String sql = "UPDATE users SET username=?, password=?, email=? WHERE id=?";
try (Connection conn = getConnection();
PreparedStatement pstmt = conn.prepareStatement(sql)) {
pstmt.setString(1, user.getUsername());
pstmt.setString(2, user.getPassword());
pstmt.setString(3, user.getEmail());
pstmt.setInt(4, user.getId());
pstmt.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
}
public void deleteUser(int id) {
String sql = "DELETE FROM users WHERE id=?";
try (Connection conn = getConnection();
PreparedStatement pstmt = conn.prepareStatement(sql)) {
pstmt.setInt(1, id);
pstmt.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
创建JSP页面
现在，我们可以创建JSP页面来展示用户列表、添加新用户、编辑用户和删除用户。
用户列表页面（users.jsp）
jsp
<%@ page import="java.util.List" %>
<%@ page import="com.example.User" %>
<%@ page import="com.example.UserDAO" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>User List</title>
</head>
<body>
<h1>User List</h1>
<table border="1">
<tr>
<th>ID</th>
<th>Username</th>
<th>Password</th>
<th>Email</th>
<th>Actions</th>
</tr>
<%
UserDAO userDAO = new UserDAO();
List<User> users = userDAO.getAllUsers();
for (User user : users) {
%>
<tr>
<td><%= user.getId() %></td>
<td><%= user.getUsername() %></td>
<td><%= user.getPassword() %></td>
<td><%= user.getEmail() %></td>
<td>
<a href="edit.jsp?id=<%= user.getId() %>">Edit</a>
<a href="delete.jsp?id=<%= user.getId() %>">Delete</a>
</td>
</tr>
<%
}
%>
</table>
<a href="add.jsp">Add New User</a>
</body>
</html>
添加新用户页面（add.jsp）
jsp
<%@ page import="com.example.User" %>
<%@ page import="com.example.UserDAO" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Add User</title>
</head>
<body>
<h1>Add User</h1>
<form action="add_process.jsp" method="post">
Username: <input type="text" name="username"><br>
Password: <input type="password" name="password"><br>
Email: <input type="email" name="email"><br>
<input type="submit" value="Add">
</form>
</body>
</html>
添加新用户处理页面（add_process.jsp）
jsp
<%@ page import="com.example.User" %>
<%@ page import="com.example.UserDAO" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Add User Process</title>
</head>
<body>
<%
String username = request.getParameter("username");
String password = request.getParameter("password");
String email = request.getParameter("email");
User user = new User();
user.setUsername(username);
user.setPassword(password);
user.setEmail(email);
UserDAO userDAO = new UserDAO();
userDAO.addUser(user);
response.sendRedirect("users.jsp");
%>
</body>
</html>
编辑用户页面（edit.jsp）
jsp
<%@ page import="com.example.User" %>
<%@ page import="com.example.UserDAO" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Edit User</title>
</head>
<body>
<h1>Edit User</h1>
<%
int id = Integer.parseInt(request.getParameter("id"));
UserDAO userDAO = new UserDAO();
User user = userDAO.getUserById(id);
%>
<form action="update_process.jsp" method="post">
Username: <input type="text" name="username" value="<%= user.getUsername() %>"><br>
Password: <input type="password" name="password" value="<%= user.getPassword() %>"><br>
Email: <input type="email" name="email" value="<%= user.getEmail() %>"><br>
<input type="hidden" name="id" value="<%= user.getId() %>">
<input type="submit" value="Update">
</form>
</body>
</html>
编辑用户处理页面（update_process.jsp）
jsp
<%@ page import="com.example.User" %>
<%@ page import="com.example.UserDAO" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Update User Process</title>
</head>
<body>
<%
int id = Integer.parseInt(request.getParameter("id"));
String username = request.getParameter("username");
String password = request.getParameter("password");
String email = request.getParameter("email");
User user = new User();
user.setId(id);
user.setUsername(username);
user.setPassword(password);
user.setEmail(email);
UserDAO userDAO = new UserDAO();
userDAO.updateUser(user);
response.sendRedirect("users.jsp");
%>
</body>
</html>
删除用户页面（delete.jsp）
jsp
<%@ page import="com.example.UserDAO" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Delete User</title>
</head>
<body>
<%
int id = Integer.parseInt(request.getParameter("id"));
UserDAO userDAO = new UserDAO();
userDAO.deleteUser(id);
response.sendRedirect("users.jsp");
%>
</body>
</html>
总结
通过以上示例，我们展示了如何使用JSP和JavaBean来实现数据的增删改操作。在实际项目中，你可能需要添加更多的功能，如用户认证、权限控制等。为了提高代码的可维护性和可扩展性，建议使用框架（如Spring MVC）来简化开发过程。希望本文能帮助你更好地理解JSP在数据管理方面的应用。
Comments NOTHING