struts中html:options的使用

<html:options>

html:options was born to use data in an ArrayList. Do NOT use a Vector, because it is Synchronized and will cause problems if more than one person uses your app at a time.

Given that you have a list of products with their product ID, make a drop-down that returns the product ID. First you set up your data in your controller:

ArrayList prod = new ArrayList();
prod.add( new org.apache.struts.util.LabelValueBean( "Widget", "20" ) );
prod.add( new org.apache.struts.util.LabelValueBean( "Sprocket", "29-2a" ) );
prod.add( new org.apache.struts.util.LabelValueBean( "Cog", "29s" ) );
prod.add( new org.apache.struts.util.LabelValueBean( "Dunsel", "943" ) );

LabelValueBean takes the first String argument as the displayed name and the second as the value returned. We’ll see more about this in a bit.

Now that you have prod set up, you pass that as a session or request bean to the JSP.

request.setAttribute( Constants.PRODUCT_KEY, prod );

(the Constants.PRODUCT_KEY is set to our bean name: "products"; we use this to centralize bean name management)

To use the data in the JSP, add the following code:

  <html:select property="product_id" styleClass="prodselect" >
    <html:options collection="products" property="value" labelProperty="label" />
  </html:select>

Notes: product_id is the variable the JSP will set to the product ID value of the product selected by the user. products is the name of the bean (it must match what is in Contants.PRODUCT_KEY -- we probably could've said

... collection="<%= Constants.PRODUCT_KEY %>" ...

in place of hard-coding the name. The choice is up to you.

property="value" and labelProperty="label" are automatically set by org.apache.struts.util.LabelValueBean, so only use the values shown here.

The resulting HTML will look something like:

<select name="product_id" size="1">
<option value="20">Widget</option>
<option value="29-2a">Sprocket</option>
<option value="29s">Cog</option>
<option value="943">Dunsel</option>
</select>

Which renders as WidgetSprocketCogDunsel