jsp+serverlet+jdbc+mysql实现增删改查

首先，需要创建一个数据库和对应的表。假设我们创建了一个名为“student”的数据库，其中有一个名为“student_info”的表，包含id、name、age和gender四个字段。

接下来，需要创建一个Java Web项目，将mysql-connector-java包添加到项目中。

在项目中创建一个servlet，并在web.xml中进行配置。

在servlet中，使用JDBC连接数据库，并实现增删改查操作。下面是一个示例代码：

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
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 StudentServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    private Connection conn = null;
    private PreparedStatement pstmt = null;
    private ResultSet rs = null;

    // 连接数据库
    private void getConnection() {
        String driver = "com.mysql.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/student";
        String user = "root";
        String password = "123456";

        try {
            Class.forName(driver);
            conn = DriverManager.getConnection(url, user, password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 关闭资源
    private void close() {
        try {
            if (rs != null) {
                rs.close();
            }
            if (pstmt != null) {
                pstmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 查询
    private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        getConnection();

        String sql = "SELECT * FROM student_info";
        try {
            pstmt = conn.prepareStatement(sql);
            rs = pstmt.executeQuery();

            while (rs.next()) {
                out.println(rs.getInt("id") + " " + rs.getString("name") + " " + rs.getInt("age") + " " + rs.getString("gender"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 插入
    private void insert(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        getConnection();

        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String gender = request.getParameter("gender");

        String sql = "INSERT INTO student_info(id, name, age, gender) VALUES(?, ?, ?, ?)";
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            pstmt.setString(2, name);
            pstmt.setInt(3, age);
            pstmt.setString(4, gender);

            int count = pstmt.executeUpdate();
            if (count > 0) {
                out.println("插入成功！");
            } else {
                out.println("插入失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 更新
    private void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        getConnection();

        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String gender = request.getParameter("gender");

        String sql = "UPDATE student_info SET name=?, age=?, gender=? WHERE id=?";
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1, name);
            pstmt.setInt(2, age);
            pstmt.setString(3, gender);
            pstmt.setInt(4, id);

            int count = pstmt.executeUpdate();
            if (count > 0) {
                out.println("更新成功！");
            } else {
                out.println("更新失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    // 删除
    private void delete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();

        getConnection();

        int id = Integer.parseInt(request.getParameter("id"));

        String sql = "DELETE FROM student_info WHERE id=?";
        try {
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);

            int count = pstmt.executeUpdate();
            if (count > 0) {
                out.println("删除成功！");
            } else {
                out.println("删除失败！");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            close();
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        String op = request.getParameter("op");

        if ("query".equals(op)) {
            query(request, response);
        } else if ("insert".equals(op)) {
            insert(request, response);
        } else if ("update".equals(op)) {
            update(request, response);
        } else if ("delete".equals(op)) {
            delete(request, response);
        }
    }

}

在jsp页面中，可以通过表单提交数据，并调用对应的servlet实现增删改查操作。例如：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <form action="StudentServlet" method="post">
        <input type="hidden" name="op" value="insert">
        ID：<input type="text" name="id"><br>
        姓名：<input type="text" name="name"><br>
        年龄：<input type="text" name="age"><br>
        性别：<input type="text" name="gender"><br>
        <input type="submit" value="插入">
    </form>

    <form action="StudentServlet" method="post">
        <input type="hidden" name="op" value="query">
        <input type="submit" value="查询">
    </form>

    <form action="StudentServlet" method="post">
        <input type="hidden" name="op" value="update">
        ID：<input type="text" name="id"><br>
        姓名：<input type="text" name="name"><br>
        年龄：<input type="text" name="age"><br>
        性别：<input type="text" name="gender"><br>
        <input type="submit" value="更新">
    </form>

    <form action="StudentServlet" method="post">
        <input type="hidden" name="op" value="delete">
        ID：<input type="text" name="id"><br>
        <input type="submit" value="删除">
    </form>
</body>
</html>

以上代码实现了一个简单的增删改查功能。需要注意的是，这只是一个示例，实际应用中需要根据具体情况进行修改。