java - 哪个地方写connection.close()和preparedstatement.close()

Question

我是 JDBC 新手...

Student类有Constructor、add()、update()和delete()等方法...

在构造函数中打开连接。下面代码中的 conn.close() 和 pstmt.close() 写在哪个位置帮助我

class Student
{
    Connection conn;

    PreparedStatement  pstmt;

    ResultSet rs;

    public Student()
    {
        try
        {
            Class.forName("com.mysql.jdbc.Driver");

            conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
        }
        catch(Exception e)
        {
             System.out.println("Error :"+e.getMessage());
        }

    }


    public void add(int rollno,String name)
    {
        try
        {
            pstmt = conn.prepareStatement("insert into student values (?, ?)");

            pstmt.setInt(1,rollno);

            pstmt.setString(2, name);

            int i = pstmt.executeUpdate();

            if (i != 0) {
                System.out.println("Record Inserted");
            } else {
                System.out.println("Record Not Inserted");
            }

        }
        catch(Exception e)
        {
             System.out.println("Error :"+e.getMessage());
        }

    }

    public void update(int rollno,String name)
    {
        try
        {
            pstmt = conn.prepareStatement("update student set name=? where rollno=?");

            pstmt.setString(1, name);

            pstmt.setInt(2,rollno);


            int i = pstmt.executeUpdate();

            if (i != 0) {
                System.out.println("Record Updated");
            } else {
                System.out.println("Record Not Updated");
            }


        }
        catch(Exception e)
        {
             System.out.println("Error :"+e.getMessage());
        }
    }

    public void delete(int rollno)
    {
        try
        {
            pstmt = conn.prepareStatement("delete from student where rollno=?");

            pstmt.setInt(1,rollno);


            int i = pstmt.executeUpdate();

            if (i != 0) {
                System.out.println("Record Deleted");
            } else {
                System.out.println("Record Not Deleted");
            }

        }
        catch(Exception e)
        {
             System.out.println("Error :"+e.getMessage());
        }
    }

}

Answer 1

我想您应该添加另一个方法来关闭连接，并在完成操作后在对象上调用它。

public void closeConnection() {
    conn.close();
}

另外，最好创建另一个方法来打开连接，而不是从构造函数中打开它。