jsp增删查改代码

JSP（JavaServer Pages）是一种用于创建动态Web内容的技术，它允许开发者在HTML页面中嵌入Java代码。以下是一个简单的JSP增删查改（CRUD）操作的示例代码，包括数据库连接和基本的SQL操作。

基础概念

JSP：JavaServer Pages，用于创建动态Web页面。
CRUD：增（Create）、删（Read）、改（Update）、查（Delete），是数据库操作的四种基本功能。

示例代码

数据库连接类（DBConnection.java）

import java.sql.*;

public class DBConnection {
    private static final String URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String USER = "username";
    private static final String PASSWORD = "password";

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL, USER, PASSWORD);
    }
}

JSP页面示例（crud.jsp）

<%@ page import="java.sql.*" %>
<%@ page import="DBConnection" %>
<html>
<head>
    <title>CRUD Operations</title>
</head>
<body>
    <h1>CRUD Operations Example</h1>

    <!-- Create -->
    <form action="crud.jsp" method="post">
        Name: <input type="text" name="name"><br>
        Email: <input type="text" name="email"><br>
        <input type="hidden" name="action" value="create">
        <input type="submit" value="Add">
    </form>

    <!-- Read -->
    <%
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            conn = DBConnection.getConnection();
            stmt = conn.createStatement();
            rs = stmt.executeQuery("SELECT * FROM users");
    %>
        <table border="1">
            <tr>
                <th>ID</th>
                <th>Name</th>
                <th>Email</th>
                <th>Actions</th>
            </tr>
            <% while (rs.next()) { %>
                <tr>
                    <td><%= rs.getInt("id") %></td>
                    <td><%= rs.getString("name") %></td>
                    <td><%= rs.getString("email") %></td>
                    <td>
                        <form action="crud.jsp" method="post">
                            <input type="hidden" name="id" value="<%= rs.getInt("id") %>">
                            <input type="hidden" name="action" value="delete">
                            <input type="submit" value="Delete">
                        </form>
                        <form action="crud.jsp" method="post">
                            <input type="hidden" name="id" value="<%= rs.getInt("id") %>">
                            <input type="hidden" name="action" value="update">
                            <input type="submit" value="Update">
                        </form>
                    </td>
                </tr>
            <% } %>
        </table>
    <%
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (rs != null) rs.close();
            if (stmt != null) stmt.close();
            if (conn != null) conn.close();
        }
    %>

    <!-- Update -->
    <%
        String action = request.getParameter("action");
        if ("update".equals(action)) {
            int id = Integer.parseInt(request.getParameter("id"));
            String name = request.getParameter("name");
            String email = request.getParameter("email");
            try {
                conn = DBConnection.getConnection();
                String sql = "UPDATE users SET name=?, email=? WHERE id=?";
                PreparedStatement pstmt = conn.prepareStatement(sql);
                pstmt.setString(1, name);
                pstmt.setString(2, email);
                pstmt.setInt(3, id);
                pstmt.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    %>

    <!-- Delete -->
    <%
        if ("delete".equals(action)) {
            int id = Integer.parseInt(request.getParameter("id"));
            try {
                conn = DBConnection.getConnection();
                String sql = "DELETE FROM users WHERE id=?";
                PreparedStatement pstmt = conn.prepareStatement(sql);
                pstmt.setInt(1, id);
                pstmt.executeUpdate();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    %>
</body>
</html>