Question

我正在尝试创建一个表单，卖家可以插入新项目，新类别和删除项目。现在我有DELETE的问题。这是我的代码，如果有人知道如何解决它，请帮助。

String id = "42";

    try
        {
            Class.forName("com.mysql.jdbc.Driver");
            Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/projekat","root","");

            PreparedStatement prepared_statement = connection.prepareStatement("DELETE FROM artikli WHERE id= ? ;");
            prepared_statement.setString(1, id);
            int result_set = prepared_statement.executeUpdate();
            if (result_set > 0)
            {
                System.out.println("Deleted");
            }
            else
            {
                System.out.println("Can't delete");
            }
} catch (Exception ex) {
    System.out.println(ex);
}

Answer 1

试试这个：

String id = request.getParameter("id");

        try
            {
                Class.forName("com.mysql.jdbc.Driver");
                Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/projekat","root","");
                PreparedStatement prepared_statement = null;

                String strQuery = "DELETE FROM artikli WHERE id= ?";
                prepared_statement = connection.prepareStatement(strQuery);
                prepared_statement.setString(1, id);
                int result_set = prepared_statement.executeUpdate();

                if (result_set > 0)
                {
                    // System.out.println(result_set);                    
                    response.sendRedirect("Prodaja2.jsp");
                }
                else
                {
                    // System.out.println(result_set);
                    response.sendRedirect("Prodaja2.jsp?error=Can'tDelete");
                }
    } catch (Exception ex) {
        out.print(ex);
    } finally {
        try {
            stmtProd.close();
            connection.close();
        } catch (Exception ex) {
            System.out.println(ex.getMessage());
        }
    }
}


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

在您的代码中，查询后面的分号可能会有冲突。并且也不要忘记关闭创建的finally块中的连接，因为它可能导致资源泄漏，即使用户注销，连接也将保持活动状态。

Answer 2

这里有一个错误，就是你的语法

更改代码

 PreparedStatement prepared_statement = connection.prepareStatement("DELETE FROM artikli WHERE id= ? ;");

到

 PreparedStatement prepared_statement = connection.prepareStatement("DELETE FROM artikli WHERE id= ?");

如果没有其他错误，请检查id中的值，有可能为空值。

如何使用JDBC从数据库中删除数据

2 个答案: