📄 入門 21 - validator伺服端驗證 - javaworld@tw.htm
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Validator伺服端驗證</SPAN> </DIV>
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<DIV class=pagesubheading>Last changed on Oct 27, 2004 by <A
href="http://www.javaworld.com.tw/confluence/display/~koji">koji
lin</A>
</DIV><!-- page content --> 如果要驗證使用者的輸入，光使用客戶端驗證是不保險的，客戶端可能跳過輸入頁面，直接對伺服器發送請求不正確的請求，如果伺服端沒有驗證請求，就會導致錯誤。
<BR> 要使用Validator伺服端驗證，只要繼承org.apache.struts.validator.ValidatorForm類別來撰寫ActionForm就可以了，ValidatorForm是ActionForm的子類別，它重新定義了validate()方法，使用ValidatorForm定義了類別之後，在validation.xml中的設定與前一個主題相同。
<BR> ActionServlet會呼叫validate()方法，如果驗證有誤，則會收集相關的錯誤訊息並儲存在ActionErrors中傳回，您要作的是指定struts-config.xml中ActionMapping的type屬性，提供一個訊息頁面，在當中使用<html:errors/>標籤顯示錯誤訊息，例如：
<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>struts-config.xml</B></DIV>
<DIV class=codeContent><PRE><action
path=<SPAN class=java-quote>"/LoginAction"</SPAN>
type=<SPAN class=java-quote>"onlyfun.caterpillar.LoginAction"</SPAN>
name=<SPAN class=java-quote>"userForm"</SPAN>
validate=<SPAN class=java-quote>"<SPAN class=java-keyword>true</SPAN>"</SPAN>
input=<SPAN class=java-quote>"/pages/welcome.jsp"</SPAN>>
<forward
name=<SPAN class=java-quote>"greeting"</SPAN>
path=<SPAN class=java-quote>"/pages/greeting.jsp"</SPAN>/>
</action></PRE></DIV></DIV><BR>
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<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>
<head>
<title><bean:message key=<SPAN class=java-quote>"welcome.title"</SPAN>/></title>
<html:base/>
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