Struts2 How to set default checked items

The following properties are commonly used in the STRUTS2 select tag:
(1) in the Select tag in Struts2, only one of the properties that must be set is a list.
(2) The list in the select tag must have a value, or it will be an error. If there is no value, you can add Headerkey, Headervalue, so you can pass. Even if there is a value in the list, we usually add Headerkey, Headervalue, which is the first option shown in the list. Note that Headerkey cannot be empty and cannot be-1.
(3) List property: typically defined in action, it must be a source that can be iterated, such as a list, Map, set, and so on. If it is a map, then the map key corresponds to the value in Value,map in the select tag corresponding to option in the select tag. And if it is a list or a set, it can be specified by Listkey and ListValue.
(4) Listkey and Listvalue:listkey correspond to value in the Select tag, listvalue that corresponds to option in the select tag.
(5) Name property: That is, the name of the select in the form.
If you can write dead on the JSP page, you can: <s:select list= "#{1: ' Male ', 2: ' Female '}" listkey= "key" listvalue= "value" value= "2"/>
The code runs the result: "Female" is displayed by default.
If the default entry is uploaded from the background to the foreground, you can: JSP:
<s:select list= "#{' 1 ': ' Male ', ' 2 ': ' Female '}" name= "Sex"/>
Action
Private String sex;
The sex attribute has a get/set method.
Set the sex = "2" in the Business method, and select will be selected by default.