📄 入門 09 - 使用dynaactionform類別 - javaworld@tw.htm
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<DIV class=codeHeader
style="BORDER-BOTTOM-STYLE: solid"><B>LoginAction.java</B></DIV>
<DIV class=codeContent><PRE><SPAN class=java-keyword>package</SPAN> onlyfun.caterpillar;
<SPAN class=java-keyword>import</SPAN> javax.servlet.http.*;
<SPAN class=java-keyword>import</SPAN> org.apache.struts.action.*;
<SPAN class=java-keyword>public</SPAN> class LoginAction <SPAN class=java-keyword>extends</SPAN> Action {
<SPAN class=java-keyword>public</SPAN> ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
<SPAN class=java-keyword>throws</SPAN> Exception {
DynaActionForm dynaForm = (DynaActionForm) form;
<SPAN class=java-object>String</SPAN> name = (<SPAN class=java-object>String</SPAN>) dynaForm.get(<SPAN class=java-quote>"name"</SPAN>);
<SPAN class=java-object>String</SPAN> password = (<SPAN class=java-object>String</SPAN>) dynaForm.get(<SPAN class=java-quote>"password"</SPAN>);
<SPAN class=java-keyword>if</SPAN>(name.equals(<SPAN class=java-quote>"caterpillar"</SPAN>) && password.equals(<SPAN class=java-quote>"1234"</SPAN>)) {
request.setAttribute(<SPAN class=java-quote>"valid_user"</SPAN>, form);
<SPAN class=java-keyword>return</SPAN> mapping.findForward(<SPAN class=java-quote>"greeting"</SPAN>);
}
<SPAN class=java-keyword>return</SPAN> mapping.findForward(<SPAN class=java-quote>"welcome"</SPAN>);
}
}</PRE></DIV></DIV><BR> 在視圖的取值上，DynaActionForm也可以使用<bean:write>來寫出其指定的屬性值，如果您要使用EL來取得屬性值，則必須先取得map物件再指定屬性名稱，例如
${valid_user.map.name} ，下面是gretting.jsp的內容示範：
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<DIV class=codeHeader
style="BORDER-BOTTOM-STYLE: solid"><B>greeting.jsp</B></DIV>
<DIV class=codeContent><PRE><%@ taglib uri=<SPAN class=java-quote>"/tags/struts-bean"</SPAN> prefix=<SPAN class=java-quote>"bean"</SPAN> %>
<%@ taglib uri=<SPAN class=java-quote>"/tags/struts-html"</SPAN> prefix=<SPAN class=java-quote>"html"</SPAN> %>
<%@ taglib uri=<SPAN class=java-quote>"/tags/struts-logic"</SPAN> prefix=<SPAN class=java-quote>"logic"</SPAN> %>
<%@page contentType=<SPAN class=java-quote>"text/html; charset=Big5"</SPAN>%>
<html:html locale=<SPAN class=java-quote>"<SPAN class=java-keyword>true</SPAN>"</SPAN>>
<head>
<title><bean:message key=<SPAN class=java-quote>"welcome.title"</SPAN>/></title>
<html:base/>
</head>
<body bgcolor=<SPAN class=java-quote>"white"</SPAN>>
<logic:present scope=<SPAN class=java-quote>"request"</SPAN> name=<SPAN class=java-quote>"valid_user"</SPAN>>
<bean:write name=<SPAN class=java-quote>"valid_user"</SPAN> property=<SPAN class=java-quote>"name"</SPAN>/>您好，這是您的神秘禮物！
${ valid_user.map.name }, ${ valid_user.map.password}
</logic:present>
<logic:notPresent scope=<SPAN class=java-quote>"request"</SPAN> name=<SPAN class=java-quote>"valid_user"</SPAN>>
<html:link forward=<SPAN class=java-quote>"welcome"</SPAN>>請先登入</html:link>
</logic:notPresent>
</body>
</html:html></PRE></DIV></DIV><BR> Welcome.jsp的內容與之前的主題相同。<BR> DynaActionForm預設並沒有為validate()方法提供任何行為，如果需要的話，您可以透過繼承DynaActionForm來定義validate()方法，並於<form-bean>的type中設定為您所撰寫的類別。<BR> 使用DynaActionForm相當方便，但也必須付出代價，不可避免的，您的strut-config.xml內容將變得冗長，而另一方面，
DynaActionForm使用Map來查找屬性，所付出的是效能的降低，如果您的ActionForm經常使用，建議還是使用繼承
ActionForm的方法來使用表單物件。: <!-- page content ends --><!--<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/"><rdf:Description rdf:about="http://www.javaworld.com.tw/confluence/pages/viewpage.action?pageId=483" dc:identifier="http://www.javaworld.com.tw/confluence/pages/viewpage.action?pageId=483" dc:title="入門 09 - 使用DynaActionForm類別" trackback:ping="http://www.javaworld.com.tw/confluence/rpc/trackback/483"/></rdf:RDF>-->
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(5) <BR><A
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href="http://www.google.com/search?hl=zh-CN&ie=UTF-8&q=+%3Caction+type%3D%22org.apache.struts.actions.ForwardAction%22+parameter&lr=lang_zh-CN">Google:
<ACTION
title=http://www.google.com/search?q=ACTIONFORM&hl=zh-CN&lr=lang_zh-CN&ie=UTF-8&newwindow=1&start=10&sa=N
search?q='ACTIONFORM&hl=zh-CN&lr=lang_zh-CN&ie=UTF-8&newwindow=1&start=10&sa=N"'
www.google.com http:
type="org.ap...</a> (4) <br/> <a href=">Google:
ACTIONFORM</A> (4) <BR><A
title=http://www.google.com/search?hl=zh-CN&newwindow=1&q=DynaActionForm&btnG=%E6%90%9C%E7%B4%A2&lr=
href="http://www.google.com/search?hl=zh-CN&newwindow=1&q=DynaActionForm&btnG=%E6%90%9C%E7%B4%A2&lr=">Google:
DynaActionForm</A> (4) <BR><A
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href="http://www.google.com/search?q=bean:write&hl=zh-CN&lr=lang_zh-CN&ie=UTF-8&newwindow=1&start=10&sa=N">Google:
bean:write</A> (3) <BR></SPAN>
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