📄 入門 08 - actionerror與actionmessage - javaworld@tw.htm
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HttpServletResponse response)
<SPAN class=java-keyword>throws</SPAN> Exception {
<SPAN class=java-object>String</SPAN> name = (<SPAN class=java-object>String</SPAN>) PropertyUtils.getSimpleProperty(form, <SPAN class=java-quote>"name"</SPAN>);
<SPAN class=java-object>String</SPAN> password = (<SPAN class=java-object>String</SPAN>) PropertyUtils.getSimpleProperty(form, <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>))) {
ActionMessages messages = <SPAN class=java-keyword>new</SPAN> ActionMessages();
messages.add(ActionMessages.GLOBAL_MESSAGE,
<SPAN class=java-keyword>new</SPAN> ActionMessage(<SPAN class=java-quote>"message.namepass.notmatched"</SPAN>));
saveMessages(request, messages);
<SPAN class=java-keyword>return</SPAN> mapping.findForward(<SPAN class=java-quote>"welcome"</SPAN>);
}
<SPAN class=java-keyword>else</SPAN> {
request.getSession().setAttribute(<SPAN class=java-quote>"valid_user"</SPAN>, form);
<SPAN class=java-keyword>return</SPAN> mapping.findForward(<SPAN class=java-quote>"greeting"</SPAN>);
}
}
}</PRE></DIV></DIV><BR> 在這次的程式中，我們使用了org.apache.commons.beanutils中的PropertyUtils類別來協助我們取
ActionForm中的值，好處是不用理會ActionForm真正的形態，PropertyUtils會自動幫我們判斷，
getSimpleProperty()傳回的是Object，我們將之轉換為String。<BR> ActionMessages是Struts
1.1所新增的類別，它變成了ActionErrors的父類別，同樣的，ActionMessage也是Struts
1.1新增的類別，它是ActionError的父類別，資料的格式與完整性檢查在ActionForm中我們已經驗證了，接下來我們在Action中檢查是否符合名稱與密碼，如果不符合就加入相關的訊息。<BR> 在Struts
1.1中特意將Message與Error區別，該是認定所謂的Error是使用者的輸入在完整性或格式等上有誤，而Message是指輸入的資料基本上沒有錯誤，但不能符合後續的商務處理。<BR> 為了要能夠顯示錯誤與訊息，我們必須在application_zh.properties中加入key-value對應，如下：
<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>application_zh.properties</B></DIV>
<DIV class=codeContent><PRE># -- error --
error.name.required=沒有輸入名稱
error.password.required=沒有輸入密碼
#-- message --
message.namepass.notmatched=名稱與密碼不正確</PRE></DIV></DIV><BR> 為了要能使用中文，記得使用native2ascii工具程式進行轉換，接下來我們來看看我們的Welcome.jsp如何撰寫，要注意的是在<html:errors/>與<htm:messages/>的使用：
<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>Welcome.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> %>
<%@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>>
<html:errors/>
<html:messages id=<SPAN class=java-quote>"messages"</SPAN> message=<SPAN class=java-quote>"<SPAN class=java-keyword>true</SPAN>"</SPAN>>
<bean:write name=<SPAN class=java-quote>"messages"</SPAN>/>
</html:messages>
<h3>請登入</h3>
<html:form action=<SPAN class=java-quote>"/Login"</SPAN>>
名稱：<html:text property=<SPAN class=java-quote>"name"</SPAN> size=<SPAN class=java-quote>"20"</SPAN>/><br>
密碼：<html:password property=<SPAN class=java-quote>"password"</SPAN> size=<SPAN class=java-quote>"20"</SPAN>/><br>
<html:submit/> <html:reset/>
</html:form>
</body>
</html:html></PRE></DIV></DIV><BR> 如果由於ActionForm傳回ActionErrors物件而返回Welcome.jsp，則<html:errors/>標籤會顯示ActionErrors中的相關錯誤訊息，我們利用<html:messages/>來檢查返回中是否也包括
ActionMessages物件，如果有的話就取出並使用<bean:write/>標籤顯示之。<BR> 下面是執行時未填寫欄位所顯示的錯誤訊息的一個例子：
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<DIV class=codeContent><PRE><html lang=<SPAN class=java-quote>"zh"</SPAN>>
<head>
<title>哈囉！Struts！</title>
<base href=<SPAN class=java-quote>"http:<SPAN class=java-comment>//localhost:8080/HelloStruts/pages/Welcome.jsp"</SPAN>></SPAN>
</head>
<body bgcolor=<SPAN class=java-quote>"white"</SPAN>>
<UL>
<LI>沒有輸入名稱
</LI><LI>沒有輸入密碼
</LI></UL>
<h3>請登入</h3>
<form name=<SPAN class=java-quote>"UserForm"</SPAN> method=<SPAN class=java-quote>"post"</SPAN> action=<SPAN class=java-quote>"/HelloStruts/Login.<SPAN class=java-keyword>do</SPAN>"</SPAN>>
名稱：<input type=<SPAN class=java-quote>"text"</SPAN> name=<SPAN class=java-quote>"name"</SPAN> size=<SPAN class=java-quote>"20"</SPAN> value=<SPAN class=java-quote>""><br>
密碼：<input type="</SPAN>password<SPAN class=java-quote>" name="</SPAN>password<SPAN class=java-quote>" size="</SPAN>20<SPAN class=java-quote>" value="</SPAN><SPAN class=java-quote>"><br>
<input type="</SPAN>submit<SPAN class=java-quote>" value="</SPAN>Submit<SPAN class=java-quote>"> <input type="</SPAN>reset<SPAN class=java-quote>" value="</SPAN>Reset">
</form>
</body>
</html></PRE></DIV></DIV><BR> 注意到ActionErrors在Struts
1.2之後可能會被標示為deprecated，將來可能會改以ActionMessages取代，所以<html:errors/>在將來必須以下面的方式來取代：
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<DIV class=codeContent><PRE><html:messages id=<SPAN class=java-quote>"msg"</SPAN> >
<bean:write name=<SPAN class=java-quote>"msg"</SPAN>/>
</html:messages></PRE></DIV></DIV><BR> 在之前的例子中，在<html:messages/>的屬性上設定message為true，這表示顯示ActionMessages的內容：代碼:
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<DIV class=codeContent><PRE><html:messages id=<SPAN class=java-quote>"messages"</SPAN> message=<SPAN class=java-quote>"<SPAN class=java-keyword>true</SPAN>"</SPAN>>
<bean:write name=<SPAN class=java-quote>"messages"</SPAN>/>
</html:messages></PRE></DIV></DIV><!-- 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=481" dc:identifier="http://www.javaworld.com.tw/confluence/pages/viewpage.action?pageId=481" dc:title="入門 08 - ActionError與ActionMessage" trackback:ping="http://www.javaworld.com.tw/confluence/rpc/trackback/481"/></rdf:RDF>-->
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