【小题大做】 Antipattern: Magic Page

2005-09-12 by 开心就好

Bruce Tate 在他的书《Bitter Java》里谈到了Server-side Java 中的 antipatterns ，其中一个叫做“Magic Servlet” 。在这个Servlet 里，混杂了model，view和controller的编码，搞得责任不清，维护或扩展起来很麻烦。

其实在ASP.NET世界里也一样，如果你在论坛上混长了，类似下面的编码随处可见，我们不妨叫它为 “ Magic Page”，。问题是，这些红字的语句是否应该出现在这里？

(注：我知道这是个样品程序而已，求全责备恐怕是有点荒唐，但类似的编码在论坛上的帖子里经常出现，到底是什么原因呢？是程序员技术不精还是模仿造成的？)

\<%@ Import Namespace="System.Data" %>
\<%@ Import Namespace="System.Data.SqlClient" %>

\<html>

\<head>

SqlConnection myConnection;
public Hashtable StateIndex;

protected void Page_Load(Object Src, EventArgs E)
{
 myConnection = new SqlConnection("server=(local)\NetSDK;database=pubs;Trusted_Connection=yes");

if (!IsPostBack)
BindGrid();

StateIndex = new Hashtable();
 StateIndex["CA"] = 0;
 StateIndex["IN"] = 1;
 StateIndex["KS"] = 2;
 StateIndex["MD"] = 3;
 StateIndex["MI"] = 4;
 StateIndex["OR"] = 5;
 StateIndex["TN"] = 6;
 StateIndex["UT"] = 7;
 }

public void MyDataGrid_Edit(Object sender, DataGridCommandEventArgs E)
    {
        MyDataGrid.EditItemIndex = (int)E.Item.ItemIndex;
        BindGrid();
    }

public void MyDataGrid_Cancel(Object sender, DataGridCommandEventArgs E)
    {
        MyDataGrid.EditItemIndex = -1;
        BindGrid();
    }

public void MyDataGrid_Update(Object sender, DataGridCommandEventArgs E)
 {
 if (Page.IsValid)
 {
String updateCmd = "UPDATE Authors SET au_id = \@Id, au_lname = \@LName, au_fname = \@FName, phone = \@Phone, "
 + "address = \@Address, city = \@City, state = \@State, zip = \@Zip, contract = \@Contract where au_id = \@Id";

 SqlCommand myCommand = new SqlCommand(updateCmd, myConnection);

 myCommand.Parameters.Add(new SqlParameter("@Id", SqlDbType.NVarChar, 11));
 myCommand.Parameters.Add(new SqlParameter("@LName", SqlDbType.NVarChar, 40));
 myCommand.Parameters.Add(new SqlParameter("@FName", SqlDbType.NVarChar, 20));
 myCommand.Parameters.Add(new SqlParameter("@Phone", SqlDbType.NChar, 12));
 myCommand.Parameters.Add(new SqlParameter("@Address", SqlDbType.NVarChar, 40));
 myCommand.Parameters.Add(new SqlParameter("@City", SqlDbType.NVarChar, 20));
 myCommand.Parameters.Add(new SqlParameter("@State", SqlDbType.NChar, 2));
 myCommand.Parameters.Add(new SqlParameter("@Zip", SqlDbType.NChar, 5));
 myCommand.Parameters.Add(new SqlParameter("@Contract", SqlDbType.NVarChar,1));

 myCommand.Parameters["@Id"].Value = MyDataGrid.DataKeys[(int)E.Item.ItemIndex];

 String[] cols = {"LName","FName","Phone","Address","City","Zip"};

 for (int i=0; i {
 String colvalue = ((TextBox)E.Item.FindControl("edit_" + cols[i])).Text;
 myCommand.Parameters["@" + cols[i]].Value = Server.HtmlEncode(colvalue);
 }

 myCommand.Parameters["@State"].Value = ((DropDownList)E.Item.FindControl("edit_State")).SelectedItem.ToString();

 if (((CheckBox)E.Item.FindControl("edit_Contract")).Checked = true)
 myCommand.Parameters["@Contract"].Value = "1";
 else
 myCommand.Parameters["@Contract"].Value = "0";

 myCommand.Connection.Open();

 try
 {
 myCommand.ExecuteNonQuery();
 Message.InnerHtml = "Record Updated
" + updateCmd;
 MyDataGrid.EditItemIndex = -1;
 }
 catch (SqlException e)
 {
 if (e.Number == 2627)
 Message.InnerHtml = "ERROR: A record already exists with the same primary key";
 else
 Message.InnerHtml = "ERROR: Could not update record, please ensure the fields are correctly filled out";
 Message.Style["color"] = "red";
 }

 myCommand.Connection.Close();

BindGrid();
        }
        else
        {
            Message.InnerHtml = "ERROR: Please check each field for error conditions.";
            Message.Style["color"] = "red";
        }
    }

private void MyDataGrid_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
    {
        if (e.Item.ItemType == ListItemType.EditItem)
        {
            for (int i = 0; i             {
                try
                {
                    if (e.Item.Controls[i].Controls[1].GetType().ToString() == "System.Web.UI.WebControls.TextBox")
                    {
                        TextBox tb = (TextBox)e.Item.Controls[i].Controls[1];
                        tb.Text = Server.HtmlDecode(tb.Text);
                    }
                }
                catch
                {

}
            }
        }
    }

public void BindGrid()
{
 SqlDataAdapter myCommand = new SqlDataAdapter("select * from Authors", myConnection);

 DataSet ds = new DataSet();
myCommand.Fill(ds, "Authors");

 MyDataGrid.DataSource=ds.Tables["Authors"].DefaultView;
 MyDataGrid.DataBind();
 }

\</head>

\<body style="font: 10pt verdana">

\<form runat="server">

\<h3>\Updating a Row of Data w/ Validation\\</h3>

\\

\<ASP:DataGrid id="MyDataGrid" runat="server"
 Width="800"
 BackColor="#ccccff"
 BorderColor="black"
 ShowFooter="false"
 CellPadding=3
 CellSpacing="0"
 Font-Name="Verdana"
 Font-Size="8pt"
 HeaderStyle-BackColor="#aaaadd"
 OnEditCommand="MyDataGrid_Edit"
 OnCancelCommand="MyDataGrid_Cancel"
 OnUpdateCommand="MyDataGrid_Update"
 DataKeyField="au_id"
 AutoGenerateColumns="false"
 OnItemDataBound="MyDataGrid_ItemDataBound"
 >

\<Columns>
 \<asp:EditCommandColumn EditText="Edit" CancelText="Cancel" UpdateText="Update" ItemStyle-Wrap="false"/>
 \<asp:BoundColumn HeaderText="au_id" SortExpression="au_id" ReadOnly="True" DataField="au_id" ItemStyle-Wrap="false"/>
 \<asp:TemplateColumn HeaderText="au_lname" SortExpression="au_lname">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "au_lname") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \
 \<asp:TextBox runat="server" id="edit_LName" Text='\<%# DataBinder.Eval(Container.DataItem, "au_lname") %>'/>
 \<asp:RequiredFieldValidator id="au_lnameReqVal"
 ControlToValidate="edit_LName"
 Display="Dynamic"
 Font-Name="Verdana" Font-Size="12"
 runat=server>

 \</asp:RequiredFieldValidator>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="au_fname" SortExpression="au_fname">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "au_fname") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \
 \<asp:TextBox runat="server" id="edit_FName" Text='\<%# DataBinder.Eval(Container.DataItem, "au_fname") %>'/>
 \<asp:RequiredFieldValidator id="au_fnameReqVal"
 ControlToValidate="edit_FName"
 Display="Dynamic"
 Font-Name="Verdana" Font-Size="12"
 runat=server>

 \</asp:RequiredFieldValidator>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="phone" SortExpression="phone">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "phone") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \
 \<asp:TextBox runat="server" id="edit_Phone" Text='\<%# DataBinder.Eval(Container.DataItem, "phone") %>'/>
 \<asp:RequiredFieldValidator id="phoneReqVal"
 ControlToValidate="edit_Phone"
 Display="Dynamic"
 Font-Name="Verdana" Font-Size="12"
 runat=server>
 *
 \</asp:RequiredFieldValidator>
 \<asp:RegularExpressionValidator id="phoneRegexVal"
 ControlToValidate="edit_Phone"
 ValidationExpression="[0-9]{3} [0-9]{3}-[0-9]{4}"
 Display="Dynamic"
 Font-Name="Arial" Font-Size="11"
 runat=server>
 * Phone must be in form: XXX XXX-XXXX \ 
 \</asp:RegularExpressionValidator>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="address" SortExpression="address">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "address") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \<asp:TextBox runat="server" id="edit_Address" Text='\<%# DataBinder.Eval(Container.DataItem, "address") %>'/>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="city" SortExpression="city">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "city") %>'/>
 &n
bsp; \</ItemTemplate>
 \<EditItemTemplate>
 \<asp:TextBox runat="server" id="edit_City" Text='\<%# DataBinder.Eval(Container.DataItem, "city") %>'/>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="state" SortExpression="state">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "state") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \<asp:DropDownList runat="server" SelectedIndex='\<%# StateIndex[(String)((DataRowView)Container.DataItem)["state"]] %>' id="edit_State">
 \<asp:ListItem>CA\</asp:ListItem>
 \<asp:ListItem>IN\</asp:ListItem>
 \<asp:ListItem>KS\</asp:ListItem>
 \<asp:ListItem>MD\</asp:ListItem>
 \<asp:ListItem>MI\</asp:ListItem>
 \<asp:ListItem>OR\</asp:ListItem>
 \<asp:ListItem>TN\</asp:ListItem>
 \<asp:ListItem>UT\</asp:ListItem>
 \</asp:DropDownList>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="zip" SortExpression="zip">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "zip") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \<asp:TextBox runat="server" id="edit_Zip" Text='\<%# DataBinder.Eval(Container.DataItem, "zip") %>'/>
 \<asp:RegularExpressionValidator id="RegularExpressionValidator1"
 ASPClass="RegularExpressionValidator" ControlToValidate="edit_Zip"
 ValidationExpression="[0-9]{5}"
 Display="Dynamic"
 Font-Name="Arial" Font-Size="11"
 runat=server>
 * Zip Code must be 5 numeric digits \ 
 \</asp:RegularExpressionValidator>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \<asp:TemplateColumn HeaderText="contract" SortExpression="contract">
 \<ItemTemplate>
 \<asp:Label runat="server" Text='\<%# DataBinder.Eval(Container.DataItem, "contract", "{0}") %>'/>
 \</ItemTemplate>
 \<EditItemTemplate>
 \<asp:CheckBox runat="server" id="edit_Contract" Checked='\<%# DataBinder.Eval(Container.DataItem, "contract") %>'/>
 \</EditItemTemplate>
 \</asp:TemplateColumn>
 \</Columns>

\</ASP:DataGrid>

\</form>

\</body>
\</html>

跟本帖子的主题不相关，在上面的例程中，还有一个不懂的地方是，每次更新一条数据，为什么需要对整个DataGrid做DataBind()？为什么不能对当前这个DataGridItem做重新DataBind()？(DataGridItem是支持DataBind()的，但无法改变当前这个DataGridItem的ItemType)。。。。。。我的看法是，选择是否对整个DataGrid重新做DataBind()应该是高层次的policy，应该由应用的需求或程序员来决定，而不应该通过控件来强制执行