# Struts2 與 JSP
[TOC]
### :triangular_flag_on_post: JSP標籤

|說明|語法|
|-|-|
|輸出|<s:property value=”#x['y']” />|

### :triangular_flag_on_post: type=”chain”

<result name="toDetail" type="chain">
    <param name="namespace">要跳轉的action的路徑</param>
    <param name="actionName">要跳轉的action的名字</param>
    <param name="method">要跳轉的method的名字</param>
</result>

範例：

   <result type="chain" name="toAaaArticle">
       <param name="namespace">/aaa/article</param>
       <param name="actionName">article/toArticle</param>
   </result>
   <result type="chain" name="toBbbArticle">
       <param name="namespace">/article</param>
       <param name="actionName">article/toArticle</param>
   </result>
   <result type="chain" name="toCccArticle">
       <param name="namespace">/ccc/article</param>
       <param name="actionName">article/toArticle</param>
   </result>
   <result type="chain" name="toArticle">
       <param name="namespace">/article</param>
       <param name="actionName">article/toArticle</param>
   </result>

### :triangular_flag_on_post: 路徑設定

<action name="網址路徑*/*" class="Action名稱" method="{位置}">
    <param name="參數名稱">{位置}</param>
    <param name="參數名稱">值</param>
    <result name="方法名稱">檔案路徑</result>
    <result name="方法名稱" type="redirect">檔案路徑</result>
</action>

範例：

<action name="new_*/*" class="newsAction" method="{2}">
	<param name="today">{1}</param>
	<param name="type_id">123</param>
	<param name="type_name">最新消息</param>
	<result name="toIndex">/WEB-INF/news/index.jsp</result>
	<result name="redirectList" type="redirect">${PATH}new_${today}/index.jsp</result>
</action>

### :triangular_flag_on_post: xml 強制報錯

<interceptors>
  <interceptor-stack name="loggingStack">
    <interceptor-ref name="defaultStack">
      <param name="exception.logEnable">true</param>
      <param name="exception.logLevel">ERROR</param>
    </interceptor-ref>
  </interceptor-stack>
</interceptors>

在該ation設定加入此段

<action name="user/*" class="userAction">
  <interceptor-ref name="loggingStack"/>
  <result name="toDetail">/WEBINF/user/detail.jsp</result>
  ...
</action>

### :triangular_flag_on_post: 使用 s:iterator
#### 1. 為 XxxAction 新增方法，並提供 getter、setter 方法

public class XxxAction {    
    private List<Product> products;

    public List<Product> getProducts() {
    return products;
    
    public void setProducts(List<Product> products) {
        this.products = products;
    }
       
    public String list() {
        products = XxxService.getList();
        return "list";
    }
}

#### 2. 於 struts.xml 設定路徑

<action name="products" class="com.winnie.action.XxxAction" method="showProducts">
    <result name="list">list.jsp</result>
</action>

#### 3. list.jsp 使用 s:iterator 跌代 products

|語法|回傳|說明|
|-|-|-|
|value |物件| Action的參數|
|var |物件的別名| 表示跌代出來的元素|
|st |物件的別名| 表示跌代出來的元素狀態|
|st.index |數字型態|表示跌代的索引值，初始值為0|
|st.count |數字型態|表示跌代的索引值，初始值為1|
|st.first |布林型態|是否為第一個元素|
|st.last |布林型態|是否為最後一個元素|
|st.odd |布林型態|是否為奇數|
|st.even |布林型態|是否為偶數|

<s:iterator value="products" var="p" status="st">
    <div>
        <p>${p.id}</p>
        <p>${p.name}</p>
        <p>${st.index}</p>
        <p>${st.count}</p>
        <p>${st.first}</p>
        <p>${st.last}</p>
        <p>${st.odd}</p>
        <p>${st.even}</p>
    </div>
</s:iterator>

---
參考資料
[Dynamic Method Invocation In Struts 2](https://www.w3schools.blog/dynamic-method-invocation-in-struts-2)
[Struts 2 Configuration File](https://www.javatpoint.com/struts-2-configuration-file)