要讓 Select 設定預設的選項可以參考 https://struts.apache.org/docs/select.html 的範例
<s:select label="Months" name="months" headerKey="-1" headerValue="Select Month" list="#{'01':'Jan', '02':'Feb', [...]}" value="selectedMonth" required="true"/>// The month id (01, 02, ...) returned by the getSelectedMonth() call// against the stack will be auto-selected範例的意是是說,當 Action 執行時,會先呼叫 getSelectedMonth() 這個 method,只要在這個 method 中回傳值,就可以有預設選項了.https://struts.apache.org/docs/select.html