常用的Struts 2.0的标志（Tag）介绍
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常用的Struts 2.0的标志（Tag）介绍
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在上一篇文章《為Struts 2.0做好準備》中，我過于詳細地介紹了Struts 2.0開發環境和運行環境的配置，所以，本文很少涉及的以上兩方面的細節。如果，您看完《為Struts 2.0做好準備》后，還有什么不明白，或者沒法運行文中例子，請聯系我。我的E-MAIL：Max.M.Yuan@gmail.com。
在介紹常用標志前，我想先從總體上，對Struts 1.x與Struts 2.0的標志庫（Tag Library）作比較。
| ? | Struts 1.x | Struts 2.0 |
| 分類 | 將標志庫按功能分成HTML、Tiles、Logic和Bean等幾部分 | 嚴格上來說，沒有分類，所有標志都在URI為“/struts-tags”命名空間下，不過，我們可以從功能上將其分為兩大類：非UI標志和UI標志 |
| 表達式語言（expression languages） | 不支持嵌入語言（EL） | OGNL、JSTL、Groovy和Velcity |
好了，我要開始介紹“常用”（這里所謂的“常用”，是指在已往工作中使用Struts里經常用到的）的標志了。
| 要在JSP中使用Struts 2.0標志，先要指明標志的引入。通過在JSP的代碼的頂部加入以下代碼可以做到這點。 <%@taglib prefix="s" uri="/struts-tags" %> |
- if、elseif和else
描述：
執行基本的條件流轉。參數：
名稱 必需 默認 類型 描述 備注 test 是 Boolean 決定標志里內容是否顯示的表達式 else標志沒有這個參數 id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
<%@?page?contentType="text/html;?charset=UTF-8"?%>
<%@?taglib?prefix="s"?uri="/struts-tags"?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN">
<html>
????<head>
????????<title>Condition?Flow</title>
????</head>
????<body>
????????<h3>Condition?Flow</h3>????????????
????????<!--
????????????這里有點小技巧：
????????????本來可以用#parameters.name[0]來獲得，請求中name的值。但是，在我實現include例子時，
????????????無論我用param標志給name賦任何值，#parameters里面不會含有任何值，所以#parameters.name也為空值。
????????????
????????????其原因為：
????????????當使用include標志時，被包含的頁面（included）里#parameters拿到的是包含頁面里的請求參數。
????????????
????????????因此，這里必須手工調用request.getParameter("name")。
????????-->
????????<s:set?name="name"?value="<%=?"'"?+?request.getParameter("name")?+?"'"?%>"?/>
????????<s:if?test="#name?==?'Max'">
????????????Max's?file?here
????????</s:if>
????????<s:elseif?test="#name?==?'Scott'">
????????????Scott's?file?here
????????</s:elseif>
????????<s:else>
????????????Other's?file?here
????????</s:else>????????
????</body>
</html>例1 condition.jsp - iterator
描述：
用于遍歷集合（java.util.Collection）或枚舉值（java.util.Iterator）。參數：
名稱 必需 默認 類型 描述 status 否 String 如果設置此參數，一個IteratorStatus的實例將會壓入每個遍歷的堆棧 value 否 Object/String 要遍歷的可枚舉的（iteratable）數據源，或者將放入新列表（List）的對象 id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
<%@?page?contentType="text/html;?charset=UTF-8"?%>
<%@?page?import="java.util.List"?%>
<%@?page?import="java.util.ArrayList"?%>
<%@?taglib?prefix="s"?uri="/struts-tags"?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN">
<%
????List?list?=?new?ArrayList();
????list.add("Max");
????list.add("Scott");
????list.add("Jeffry");
????list.add("Joe");
????list.add("Kelvin");
????request.setAttribute("names",?list);
%>
<html>
????<head>
????????<title>Iterator</title>
????</head>
????<body>
????????<h3>Names:?</h3>
????????<!--?
????????????1、此處的空property元素用于獲得當前iterator的值?
????????????2、status被設成stuts，在iterator的里面就可以通過#stuts取得IteratorStatus的對象。IteratorStatus類包含當前序號信息，如是否第一個或最后一個，是否為奇數序號。這些信息在我們做格式化的時候，顯得非常有用。
????????-->
????????<ol>
????????????<s:iterator?value="#request.names"?status="stuts">????????????????
????????????????<s:if?test="#stuts.odd?==?true">
????????????????????<li>White?<s:property?/></li>
????????????????</s:if>
????????????????<s:else>
????????????????????<li?style="background-color:gray"><s:property?/></li>
????????????????</s:else>
????????????</s:iterator>
????????</ol>
????</body>
</html>例2 iterator.jsp - i18n
描述：
加載資源包到值堆棧。它可以允許text標志訪問任何資源包的信息，而不只當前action相關聯的資源包。參數：
名稱 必需 默認 類型 描述 value 是 Object/String 資源包的類路徑（如com.xxxx.resources.AppMsg） id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
HelloWorld=Hello?Wrold!例3 classes\ ApplicationMessages.properties
<%@?page?contentType="text/html;?charset=UTF-8"?%>
<%@?taglib?prefix="s"?uri="/struts-tags"?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN">
<html>
????<head>
????????<title>Internationization</title>
????</head>
????<body>
????????<h3>
????????????<s:i18n?name="ApplicationMessages">
????????????????<s:text?name="HelloWorld"?/>
????????????</s:i18n>
????????</h3>
????</body>
</html>例3 i18n.jsp - include
描述：
包含一個servlet的輸出（servlet或jsp的頁面）。參數：
名稱 必需 默認 類型 描述 value 是 String 要包含的jsp或servlet id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
<%@?page?contentType="text/html;?charset=UTF-8"?%>
<%@?taglib?prefix="s"?uri="/struts-tags"?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN">
<html>
????<head>
????????<title>Iterator</title>
????</head>
????<body>
????????<h3>Interator?Page</h3>
????????<s:include?value="/condition.jsp">
????????????<s:param?name="name">Max</s:param>
????????</s:include>
????????<h3>i18n</h3>
????????<s:include?value="/i18n.jsp"?/>
????</body>
</html>例4 include.jsp - param
描述：
為其他標簽提供參數,比如include標簽和bean標簽. 參數的name屬性是可選的,如果提供，會調用Component的方法addParameter(String, Object), 如果不提供，則外層嵌套標簽必須實現UnnamedParametric接口(如TextTag)。value的提供有兩種方式,通過value屬性或者標簽中間的text,不同之處我們看一下例子: <param name="color">blue</param><!-- (A) --><?xml:namespace prefix = o />
<param name="color" value="blue"/><!-- (B) -->
(A)參數值會以String的格式放入statck.
(B)該值會以java.lang.Object的格式放入statck.參數：
名稱 必需 默認 類型 描述 name 否 String 參數名 value 否 String value表達式 id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
請參考例4。 - set
描述：
set標簽賦予變量一個特定范圍內的值。當希望給一個變量賦一個復雜的表達式,每次訪問該變量而不是復雜的表達式時用到。其在兩種情況下非常有用: 復雜的表達式很耗時 (性能提升) 或者很難理解 (代碼可讀性提高)。參數：
名稱 必需 默認 類型 描述 name 是 String 變量名字 scope 否 String 變量作用域,可以為application, session, request, page, 或action. value 否 Object/String 將會賦給變量的值 id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
請參考例1。 - text
描述：
支持國際化信息的標簽。國際化信息必須放在一個和當前action同名的resource bundle中,如果沒有找到相應message,tag body將被當作默認message,如果沒有tag body,message的name會被作為默認message。參數：
名稱 必需 默認 類型 描述 name 是 String 資源屬性的名字 id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
請參考例3。 - url
描述：
該標簽用于創建url,可以通過"param"標簽提供request參數。當includeParams的值時'all'或者'get', param標簽中定義的參數將有優先權,也就是說其會覆蓋其他同名參數的值。 參數： 略
例子：
<%@?page?contentType="text/html;?charset=UTF-8"?%>
<%@?taglib?prefix="s"?uri="/struts-tags"?%>
<!DOCTYPE?HTML?PUBLIC?"-//W3C//DTD?HTML?4.01?Transitional//EN">
<html>
????<head>
????????<title>URL</title>
????</head>
????<body>
????????<h3>URL</h3>????????????
????????<a?href='<s:url?value="/i18n.jsp"?/>'>i18n</a><br?/>
????????<s:url?id="url"?value="/condition.jsp">
????????????<s:param?name="name">Max</s:param>
????????</s:url>????????
????????<s:a?href="%{url}">if\elseif\else</s:a>
????</body>
</html>例5 url.jsp - property
描述：
得到'value'的屬性,如果value沒提供,默認為堆棧頂端的元素。參數：
名稱 必需 默認 類型 描述 default 否 String 如果屬性是null則顯示的default值 escape 否 true Booelean 是否escape HTML value 否 棧頂 Object 要顯示的值 id 否 Object/String 用來標識元素的id。在UI和表單中為HTML的id屬性 例子：
請參考例2。
UI標志又可以分為表單UI和非表單UI兩部分。表單UI部分基本與Struts 1.x相同，都是對HTML表單元素的包裝。不過，Struts 2.0加了幾個我們經常在項目中用到的控件如：datepicker、doubleselect、timepicker、optiontransferselect等。因為這些標志很多都經常用到，而且參數也很多，要在一篇文章詳細說明并非易事。
| 需要深入了解這些標志的朋友，可以到以下查看以下網址： http://wiki.javascud.org/display/ww2cndoc/Tags WebWork2文檔中文化計劃（中文） http://cwiki.apache.org/WW/tag-reference.html Tag Developers Guide（英文） 本文有相當的內容也來自這兩處。 |
在此，我雖然不能夠詳細講述這些標志，但是可以與大家分享一個來Struts 2.0 Show Case一個例子。
/**//*?*?$Id:?UITagExample.java?420385?2006-07-10?00:57:05Z?mrdon?$
?*
?*?Copyright?2006?The?Apache?Software?Foundation.
?*
?*?Licensed?under?the?Apache?License,?Version?2.0?(the?"License");
?*?you?may?not?use?this?file?except?in?compliance?with?the?License.
?*?You?may?obtain?a?copy?of?the?License?at
?*
?*??????http://www.apache.org/licenses/LICENSE-2.0
?*
?*?Unless?required?by?applicable?law?or?agreed?to?in?writing,?software
?*?distributed?under?the?License?is?distributed?on?an?"AS?IS"?BASIS,
?*?WITHOUT?WARRANTIES?OR?CONDITIONS?OF?ANY?KIND,?either?express?or?implied.
?*?See?the?License?for?the?specific?language?governing?permissions?and
?*?limitations?under?the?License.
?*/
package?org.apache.struts2.showcase;
import?org.apache.struts2.ServletActionContext;
import?com.opensymphony.xwork2.ActionSupport;
import?com.opensymphony.xwork2.Validateable;
import?com.opensymphony.xwork2.util.OgnlValueStack;
import?java.util.ArrayList;
import?java.util.Collections;
import?java.util.Date;
import?java.util.HashMap;
import?java.util.List;
import?java.util.Map;
import?java.io.File;
/**?*//**
?*/
public?class?UITagExample?extends?ActionSupport?implements?Validateable?{
????
????private?static?final?long?serialVersionUID?=?-94044809860988047L;????????
????String?name;
????Date?birthday;
????String?bio;
????String?favoriteColor;
????List?friends;
????boolean?legalAge;
????String?state;
????String?region;
????File?picture;
????String?pictureContentType;
????String?pictureFileName;
????String?favouriteLanguage;
????String?favouriteVehicalType?=?"MotorcycleKey";
????String?favouriteVehicalSpecific?=?"YamahaKey";
????
????List?leftSideCartoonCharacters;
????List?rightSideCartoonCharacters;
????
????List?favouriteLanguages?=?new?ArrayList();
????List?vehicalTypeList?=?new?ArrayList();
????Map?vehicalSpecificMap?=?new?HashMap();
????
????String?thoughts;
????
????public?UITagExample()?{
????????favouriteLanguages.add(new?Language("EnglishKey",?"English?Language"));
????????favouriteLanguages.add(new?Language("FrenchKey",?"French?Language"));
????????favouriteLanguages.add(new?Language("SpanishKey",?"Spanish?Language"));
????????
????????VehicalType?car?=?new?VehicalType("CarKey",?"Car");
????????VehicalType?motorcycle?=?new?VehicalType("MotorcycleKey",?"Motorcycle");
????????vehicalTypeList.add(car);
????????vehicalTypeList.add(motorcycle);
????????
????????List?cars?=?new?ArrayList();
????????cars.add(new?VehicalSpecific("MercedesKey",?"Mercedes"));
????????cars.add(new?VehicalSpecific("HondaKey",?"Honda"));
????????cars.add(new?VehicalSpecific("FordKey",?"Ford"));
????????
????????List?motorcycles?=?new?ArrayList();
????????motorcycles.add(new?VehicalSpecific("SuzukiKey",?"Suzuki"));
????????motorcycles.add(new?VehicalSpecific("YamahaKey",?"Yamaha"));
????????
????????vehicalSpecificMap.put(car,?cars);
????????vehicalSpecificMap.put(motorcycle,?motorcycles);
????}???
????????
????public?List?getLeftSideCartoonCharacters()?{
????????return?leftSideCartoonCharacters;
????}
????public?void?setLeftSideCartoonCharacters(List?leftSideCartoonCharacters)?{
????????this.leftSideCartoonCharacters?=?leftSideCartoonCharacters;
????}
????????
????public?List?getRightSideCartoonCharacters()?{
????????return?rightSideCartoonCharacters;
????}
????public?void?setRightSideCartoonCharacters(List?rightSideCartoonCharacters)?{
????????this.rightSideCartoonCharacters?=?rightSideCartoonCharacters;
????}
????????
????public?String?getFavouriteVehicalType()?{
????????return?favouriteVehicalType;
????}
????
????public?void?setFavouriteVehicalType(String?favouriteVehicalType)?{
????????this.favouriteVehicalType?=?favouriteVehicalType;
????}
????
????public?String?getFavouriteVehicalSpecific()?{
????????return?favouriteVehicalSpecific;
????}
????
????public?void?setFavouriteVehicalSpecific(String?favouriteVehicalSpecific)?{
????????this.favouriteVehicalSpecific?=?favouriteVehicalSpecific;
????}
????
????public?List?getVehicalTypeList()?{
????????return?vehicalTypeList;
????}
????
????public?List?getVehicalSpecificList()?{
????????OgnlValueStack?stack?=?ServletActionContext.getValueStack(ServletActionContext.getRequest());
????????Object?vehicalType?=?stack.findValue("top");
????????if?(vehicalType?!=?null?&&?vehicalType?instanceof?VehicalType)?{
????????????List?l?=?(List)?vehicalSpecificMap.get(vehicalType);
????????????return?l;
????????}
????????return?Collections.EMPTY_LIST;
????}
????
????public?List?getFavouriteLanguages()?{
????????return?favouriteLanguages;
????}
????public?String?execute()?throws?Exception?{
????????return?SUCCESS;
????}
????/**//*?Getters?and?Setters?*/
???????????
????public?String?doSubmit()?{
????????return?SUCCESS;
????}???????
????
????//?===?inner?class?
????public?static?class?Language?{
????????String?description;
????????String?key;
????????
????????public?Language(String?key,?String?description)?{
????????????this.key?=?key;
????????????this.description?=?description;
????????}
????????
????????public?String?getKey()?{?
????????????return?key;?
????????}
????????public?String?getDescription()?{?
????????????return?description;?
????????}
????????
????}????
????
????public?static?class?VehicalType?{
????????String?key;
????????String?description;
????????public?VehicalType(String?key,?String?description)?{
????????????this.key?=?key;
????????????this.description?=?description;
????????}
????????
????????public?String?getKey()?{?return?this.key;?}
????????public?String?getDescription()?{?return?this.description;?}
????????
????????public?boolean?equals(Object?obj)?{
????????????if?(!?(obj?instanceof?VehicalType))?{?
????????????????return?false;
????????????}
????????????else?{
????????????????return?key.equals(((VehicalType)obj).getKey());
????????????}
????????}
????????
????????public?int?hashCode()?{
????????????return?key.hashCode();
????????}
????}????
????
????public?static?class?VehicalSpecific?{
????????String?key;?
????????String?description;
????????public?VehicalSpecific(String?key,?String?description)?{
????????????this.key?=?key;
????????????this.description?=?description;
????????}
????????
????????public?String?getKey()?{?return?this.key;?}
????????public?String?getDescription()?{?return?this.description;?}
????????
????????public?boolean?equals(Object?obj)?{
????????????if?(!?(obj?instanceof?VehicalSpecific))?{
????????????????return?false;
????????????}
????????????else?{
????????????????return?key.equals(((VehicalSpecific)obj).getKey());
????????????}
????????}
????????
????????public?int?hashCode()?{
????????????return?key.hashCode();
????????}
????}
}例6 org.apache.struts2.showcase.UITagExample.java
<%@?page?contentType="text/html;?charset=UTF-8"?pageEncoding="UTF-8"?%>
<%@?taglib?prefix="s"?uri="/struts-tags"?%>
<html>
<head>
????<title>UI?Tags?Example</title>
????<s:head/>
</head>
<body>
<s:actionerror/>
<s:actionmessage/>
<s:fielderror?/>
<s:form?action="exampleSubmit"?method="post"?enctype="multipart/form-data"?tooltipConfig="#{'jsTooltipEnabled':'true'}">
????<s:textfield?
????????????label="Name"?
????????????name="name"
????????????tooltip="Enter?your?Name?here"?/>
????<s:datepicker
????????????tooltip="Select?Your?Birthday"
????????????label="Birthday"
????????????name="birthday"?/>
????<s:textarea
????????????tooltip="Enter?your?Biography"
????????????label="Biograph"
????????????name="bio"
????????????cols="20"
????????????rows="3"/>
????<s:select
????????????tooltip="Choose?Your?Favourite?Color"
????????????label="Favorite?Color"
????????????list="{'Red',?'Blue',?'Green'}"
????????????name="favoriteColor"
????????????emptyOption="true"
????????????headerKey="None"
????????????headerValue="None"/>
????<s:select
????????????tooltip="Choose?Your?Favourite?Language"
????????????label="Favourite?Language"
????????????list="favouriteLanguages"
????????????name="favouriteLanguage"
????????????listKey="key"
????????????listValue="description"
????????????emptyOption="true"
????????????headerKey="None"
????????????headerValue="None"/>
????<s:checkboxlist
????????????tooltip="Choose?your?Friends"
????????????label="Friends"
????????????list="{'Patrick',?'Jason',?'Jay',?'Toby',?'Rene'}"
????????????name="friends"/>
????<s:checkbox
????????????tooltip="Confirmed?that?your?are?Over?18"
????????????label="Age?18+"
????????????name="legalAge"/>
????<s:doubleselect
????????????tooltip="Choose?Your?State"
????????????label="State"
????????????name="region"?list="{'North',?'South'}"
????????????value="'South'"
????????????doubleValue="'Florida'"
????????????doubleList="top?==?'North'???{'Oregon',?'Washington'}?:?{'Texas',?'Florida'}"?
????????????doubleName="state"
????????????headerKey="-1"
????????????headerValue="----------?Please?Select?----------"
????????????emptyOption="true"?/>
????<s:doubleselect
????????????tooltip="Choose?your?Vehical"
????????????label="Favourite?Vehical"
????????????name="favouriteVehicalType"
????????????list="vehicalTypeList"
????????????listKey="key"
????????????listValue="description"
????????????value="'MotorcycleKey'"
????????????doubleValue="'YamahaKey'"
????????????doubleList="vehicalSpecificList"
????????????doubleListKey="key"
????????????doubleListValue="description"
????????????doubleName="favouriteVehicalSpecific"?headerKey="-1"
????????????headerValue="----------?Please?Select?----------"
????????????emptyOption="true"?/>
????<s:file
????????????tooltip="Upload?Your?Picture"
????????????label="Picture"?
????????????name="picture"?/>
????????????
????<s:optiontransferselect
????????????tooltip="Select?Your?Favourite?Cartoon?Characters"
????????????label="Favourite?Cartoons?Characters"
????????????name="leftSideCartoonCharacters"?
????????????leftTitle="Left?Title"
????????????rightTitle="Right?Title"
????????????list="{'Popeye',?'He-Man',?'Spiderman'}"?
????????????multiple="true"
????????????headerKey="headerKey"
????????????headerValue="---?Please?Select?---"
????????????emptyOption="true"
????????????doubleList="{'Superman',?'Mickey?Mouse',?'Donald?Duck'}"?
????????????doubleName="rightSideCartoonCharacters"
????????????doubleHeaderKey="doubleHeaderKey"
????????????doubleHeaderValue="---?Please?Select?---"?
????????????doubleEmptyOption="true"
????????????doubleMultiple="true"?/>
????
????<s:textarea
????????????label="Your?Thougths"
????????????name="thoughts"?
????????????tooltip="Enter?your?thoughts?here"?/>
????????????
????<s:submit?onclick="alert('aaaa');"?/>
????<s:reset?onclick="alert('bbbb');"?/>
</s:form>
????
</body>
</html>例6 example.jsp
<action?name="example"?class="org.apache.struts2.showcase.UITagExample">
????<result>example.jsp</result>
????<result?name="input">example.jsp</result>
</action>例6 struts.xml代碼片段
轉載于:https://www.cnblogs.com/fhj2050/archive/2008/04/02/1134518.html
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