【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？)
<font color="#ff0000">\<%@ Import Namespace="System.Data" %>
\<%@ Import Namespace="System.Data.SqlClient" %></font>
\<html>
\<head>
<font color="#ff0000">SqlConnection myConnection;
public Hashtable StateIndex;</font>
protected void Page_Load(Object Src, EventArgs E)
{
<font color="#ff0000"> myConnection = new SqlConnection("server=(local)\NetSDK;database=pubs;Trusted_Connection=yes");</font>
if (!IsPostBack)
BindGrid();
<font color="#ff0000">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;
</font> }
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)
{
<font color="#ff0000">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";</font>
<font color="#ff0000"> SqlCommand myCommand = new SqlCommand(updateCmd, myConnection);</font>
<font color="#ff0000"> 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));</font>
<font color="#ff0000"> myCommand.Parameters["@Id"].Value = MyDataGrid.DataKeys[(int)E.Item.ItemIndex];</font>
<font color="#ff0000"> String[] cols = {"LName","FName","Phone","Address","City","Zip"};</font>
<font color="#ff0000"> for (int i=0; i {
String colvalue = ((TextBox)E.Item.FindControl("edit_" + cols[i])).Text;
myCommand.Parameters["@" + cols[i]].Value = Server.HtmlEncode(colvalue);
}</font>
<font color="#ff0000"> myCommand.Parameters["@State"].Value = ((DropDownList)E.Item.FindControl("edit_State")).SelectedItem.ToString();</font>
<font color="#ff0000"> if (((CheckBox)E.Item.FindControl("edit_Contract")).Checked = true)
myCommand.Parameters["@Contract"].Value = "1";
else
myCommand.Parameters["@Contract"].Value = "0";</font>
<font color="#ff0000"> myCommand.Connection.Open();</font>
<font color="#ff0000"> 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";
}</font>
<font color="#ff0000"> myCommand.Connection.Close();</font>
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()
{
<font color="#ff0000"> SqlDataAdapter myCommand = new SqlDataAdapter("select * from Authors", myConnection);</font>
<font color="#ff0000"> DataSet ds = new DataSet();
myCommand.Fill(ds, "Authors");</font>
<font color="#ff0000"> MyDataGrid.DataSource=ds.Tables["Authors"].DefaultView;
MyDataGrid.DataBind();
</font> }
\</head>
\<body style="font: 10pt verdana">
\<form runat="server">
\<h3>\<font face="Verdana">Updating a Row of Data w/ Validation\</font>\</h3>
\<span id="Message" EnableViewState="false" style="font: arial 11pt;" runat="server"/>\<p>
\<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>
\<nobr>
\<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>
\<nobr>
\<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>
\<nobr>
\<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 \<br>
\</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='<font color="#ff0000">\<%# StateIndex[(String)((DataRowView)Container.DataItem)["state"]] %></font>' 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 \<br>
\</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