增（id自增） 删（根据id删除） 改（根据id修改） Java做查（根据学号查询、姓名模糊查询、查询全部）

好的，以下是Java代码实现数据库的增删改查操作：

1. 增加数据（id自增）

public void add(Student student) {
    Connection conn = null;
    PreparedStatement pstmt = null;
    try {
        // 获取数据库连接
        conn = getConnection();
        // SQL语句，id自增长，不需要插入id
        String sql = "INSERT INTO students (name, age, gender) VALUES (?, ?, ?)";
        // 创建PreparedStatement对象
        pstmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
        // 设置参数
        pstmt.setString(1, student.getName());
        pstmt.setInt(2, student.getAge());
        pstmt.setString(3, student.getGender());
        // 执行SQL语句
        pstmt.executeUpdate();
        // 获取自增长的id
        ResultSet rs = pstmt.getGeneratedKeys();
        if (rs.next()) {
            int id = rs.getInt(1);
            student.setId(id);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭连接和PreparedStatement对象
        close(conn, pstmt, null);
    }
}

2. 删除数据（根据id删除）

public void delete(int id) {
    Connection conn = null;
    PreparedStatement pstmt = null;
    try {
        // 获取数据库连接
        conn = getConnection();
        // SQL语句，根据id删除
        String sql = "DELETE FROM students WHERE id = ?";
        // 创建PreparedStatement对象
        pstmt = conn.prepareStatement(sql);
        // 设置参数
        pstmt.setInt(1, id);
        // 执行SQL语句
        pstmt.executeUpdate();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭连接和PreparedStatement对象
        close(conn, pstmt, null);
    }
}

3. 修改数据（根据id修改）

public void update(Student student) {
    Connection conn = null;
    PreparedStatement pstmt = null;
    try {
        // 获取数据库连接
        conn = getConnection();
        // SQL语句，根据id修改
        String sql = "UPDATE students SET name = ?, age = ?, gender = ? WHERE id = ?";
        // 创建PreparedStatement对象
        pstmt = conn.prepareStatement(sql);
        // 设置参数
        pstmt.setString(1, student.getName());
        pstmt.setInt(2, student.getAge());
        pstmt.setString(3, student.getGender());
        pstmt.setInt(4, student.getId());
        // 执行SQL语句
        pstmt.executeUpdate();
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭连接和PreparedStatement对象
        close(conn, pstmt, null);
    }
}

4. 查询数据（根据学号查询、姓名模糊查询、查询全部）

public List<Student> query(String sno, String name) {
    Connection conn = null;
    PreparedStatement pstmt = null;
    ResultSet rs = null;
    List<Student> list = new ArrayList<Student>();
    try {
        // 获取数据库连接
        conn = getConnection();
        // SQL语句，根据学号查询、姓名模糊查询、查询全部
        String sql = "SELECT * FROM students WHERE 1 = 1 ";
        if (!StringUtils.isEmpty(sno)) {
            sql += "AND sno = '" + sno + "' ";
        }
        if (!StringUtils.isEmpty(name)) {
            sql += "AND name LIKE '%" + name + "%' ";
        }
        // 创建PreparedStatement对象
        pstmt = conn.prepareStatement(sql);
        // 执行SQL语句
        rs = pstmt.executeQuery();
        // 处理结果集
        while (rs.next()) {
            int id = rs.getInt("id");
            String sNo = rs.getString("sno");
            String sName = rs.getString("name");
            int age = rs.getInt("age");
            String gender = rs.getString("gender");
            Student student = new Student();
            student.setId(id);
            student.setSno(sNo);
            student.setName(sName);
            student.setAge(age);
            student.setGender(gender);
            list.add(student);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    } finally {
        // 关闭连接、PreparedStatement对象和ResultSet对象
        close(conn, pstmt, rs);
    }
    return list;
}

希望这些代码对您有所帮助。