Question

public ArrayList<FeedObjects> GetFeeds(Connection connection) throws Exception
    {
        ArrayList<FeedObjects> feedData = new ArrayList<FeedObjects>();
        try
        {
            //String uname = request.getParameter("uname");
            PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website ORDER BY id DESC");
            //ps.setString(1,uname);
            ResultSet rs = ps.executeQuery();
            while(rs.next())
            {
                FeedObjects feedObject = new FeedObjects();
                feedObject.SetId(rs.getInt("id"));
                feedObject.setTitle(rs.getString("title"));
                feedObject.setDescription(rs.getString("description"));
                feedObject.setUrl(rs.getString("url"));
                feedData.add(feedObject);
            }
            return feedData;
        }
        catch(Exception e)
        {
            throw e;
        }
    }

这是我的代码，我可以从中显示employee表中的所有数据。我想要写函数，这样如果我传递id，那么我将获得相应的列值。

例如，如果我们输入id = 1，那么它应该只显示id一个emp_name。

请帮助我并修改给定的功能，以便我可以实现它。

Answer 1

然后添加WHERE clause

SELECT id,title,description,url FROM website where id= "+userId+"

返回具有该特定Id的记录，假设Id是唯一的。

看起来像

public ArrayList<FeedObjects> GetUserFeed(Connection connection, long userId) 
                                                            throws Exception

所以现在你的函数需要接收userId作为参数。

注意：不要混用两种方法。写一个单独的方法来接收用户ID 以及接收所有Feed的常用方法。

Answer 2

public ArrayList<FeedObjects> GetFeeds(Connection connection) throws Exception
    {
        ArrayList<FeedObjects> feedData = new ArrayList<FeedObjects>();
        try
        {
            //String uname = request.getParameter("uname");
            PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website where id = "<PASS ID HERE>" ORDER BY id DESC");
            //ps.setString(1,uname);
            ResultSet rs = ps.executeQuery();
            while(rs.next())
            {
                FeedObjects feedObject = new FeedObjects();
                feedObject.SetId(rs.getInt("id"));
                feedObject.setTitle(rs.getString("title"));
                feedObject.setDescription(rs.getString("description"));
                feedObject.setUrl(rs.getString("url"));
                feedData.add(feedObject);
            }
            return feedData;
        }
        catch(Exception e)
        {
            throw e;
        }
    }

试试这个

Answer 3

试试这个..

public ArrayList<FeedObjects> GetFeeds(Connection connection,int id) throws Exception
{
    ArrayList<FeedObjects> feedData = new ArrayList<FeedObjects>();
    try
    {
        //String uname = request.getParameter("uname");
        PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website where id=? ORDER BY id DESC");
        ps.setInt(1,id);
        ResultSet rs = ps.executeQuery();
        while(rs.next())
        {
            FeedObjects feedObject = new FeedObjects();
            feedObject.SetId(rs.getInt("id"));
            feedObject.setTitle(rs.getString("title"));
            feedObject.setDescription(rs.getString("description"));
            feedObject.setUrl(rs.getString("url"));
            feedData.add(feedObject);
        }
        return feedData;
    }
    catch(Exception e)
    {
        throw e;
    }
}

Answer 4

在SQL语句中添加WHERE ...

使用PreparedStatement时的正确方法是注入值而不是像这样添加它们

PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website ORDER BY id DESC WHERE id=?");
ps.setInt(1, id); //you only have 1 '?' so the index is 1, if you had another it would be 2, etc

你当然需要将你的id传递给函数。

你最好注入PreparedStatement而不是像这样追加

PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website ORDER BY id DESC WHERE id="+id);

因为那时你正在捕捉可能的SQL注入攻击。不是你现在可能不必担心的事情，但这是一种很好的做法。

Answer 5

public ArrayList<FeedObjects> GetFeeds(Connection connection, int id) throws Exception {
    //...
    PreparedStatement ps = connection.prepareStatement("SELECT id,title,description,url FROM website where id = ?");
    ps.setInt(1, id);
    ResultSet rs = ps.executeQuery();
    //...
}

如何编写函数来传递参数并获取相应的数据库值

5 个答案: