javaweb实现数据库增删改查的小项目代码

很抱歉，作为AI语言模型，我无法提供完整的JavaWeb项目代码。但是，我可以给你一些指导，帮助你实现JavaWeb项目中的增删改查功能。

下面是一个简单的示例代码，实现了一个简单的学生信息管理系统，包括增加学生信息、删除学生信息、修改学生信息和查询学生信息等功能。

首先是数据库连接的代码：

public class DBUtil {

    private static final String URL = "jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "root";

    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }

    public static void close(Connection conn, Statement stmt, ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (conn != null) {
                conn.close();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

接下来是学生信息的实体类：

public class Student {

    private int id;
    private String name;
    private int age;
    private String address;

    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 int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }
}

然后是增加学生信息的Servlet代码：

public class AddStudentServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String address = request.getParameter("address");

        Connection conn = null;
        PreparedStatement stmt = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "insert into student(id, name, age, address) values (?, ?, ?, ?)";
            stmt = conn.prepareStatement(sql);
            stmt.setInt(1, id);
            stmt.setString(2, name);
            stmt.setInt(3, age);
            stmt.setString(4, address);
            stmt.executeUpdate();
            response.sendRedirect("index.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, null);
        }
    }
}

接下来是删除学生信息的Servlet代码：

public class DeleteStudentServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));

        Connection conn = null;
        PreparedStatement stmt = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "delete from student where id=?";
            stmt = conn.prepareStatement(sql);
            stmt.setInt(1, id);
            stmt.executeUpdate();
            response.sendRedirect("index.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, null);
        }
    }
}

然后是修改学生信息的Servlet代码：

public class EditStudentServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        int age = Integer.parseInt(request.getParameter("age"));
        String address = request.getParameter("address");

        Connection conn = null;
        PreparedStatement stmt = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "update student set name=?, age=?, address=? where id=?";
            stmt = conn.prepareStatement(sql);
            stmt.setString(1, name);
            stmt.setInt(2, age);
            stmt.setString(3, address);
            stmt.setInt(4, id);
            stmt.executeUpdate();
            response.sendRedirect("index.jsp");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, null);
        }
    }
}

最后是查询学生信息的Servlet代码：

public class QueryStudentServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Student> studentList = new ArrayList<>();

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;

        try {
            conn = DBUtil.getConnection();
            String sql = "select * from student";
            stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
            while (rs.next()) {
                Student student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setAge(rs.getInt("age"));
                student.setAddress(rs.getString("address"));
                studentList.add(student);
            }
            request.setAttribute("studentList", studentList);
            request.getRequestDispatcher("index.jsp").forward(request, response);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            DBUtil.close(conn, stmt, rs);
        }
    }
}

以上代码仅供参考，具体实现可以根据自己的需求进行修改和扩展。