?? 入門 09 - 使用dynaactionform類別 - javaworld@tw.htm
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<DIV class=pageheader><SPAN class=pagetitle>入門 09 -
使用DynaActionForm類別</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 --> 一個網站中會有許多的表單以供使用者填寫資料，越大型的網站越需要更多的ActionForm物件來應付表單的取值，對於一些表單來說，ActionForm只是單純的設值、取值行為，如果為每一個表單撰寫一個ActionForm，那麼會是一件單純重複且無趣的行為，而且在維護上會更加困難。<BR> 對於一些單純的表單來說，您可以使用DynaActionForm類別，您只要在struct-config.xml中設定好相關的設定，就可以自動生成ActionForm物件，這麼一來您可以集中在struct-config.xml中管理表單物件，也可以省去不是編碼與編譯的工夫。<BR> 下面是使用DynaActionForm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=codeHeader
style="BORDER-BOTTOM-STYLE: solid"><B>struts-config.xml</B></DIV>
<DIV class=codeContent><PRE><struts-config>
<form-beans>
<form-bean
name=<SPAN class=java-quote>"userForm"</SPAN>
type=<SPAN class=java-quote>"org.apache.struts.action.DynaActionForm"</SPAN>>
<form-property
name=<SPAN class=java-quote>"name"</SPAN>
type=<SPAN class=java-quote>"java.lang.<SPAN class=java-object>String</SPAN>"</SPAN>
initial=<SPAN class=java-quote>"nobody"</SPAN>/>
<form-property
name=<SPAN class=java-quote>"password"</SPAN>
type=<SPAN class=java-quote>"java.lang.<SPAN class=java-object>String</SPAN>"</SPAN>
initial=<SPAN class=java-quote>"nopass"</SPAN>/>
</form-bean>
</form-beans>
<global-forwards>
<forward
name=<SPAN class=java-quote>"welcome"</SPAN>
path=<SPAN class=java-quote>"/Welcome.<SPAN class=java-keyword>do</SPAN>"</SPAN>/>
</global-forwards>
<action-mappings>
<action
path=<SPAN class=java-quote>"/Welcome"</SPAN>
type=<SPAN class=java-quote>"org.apache.struts.actions.ForwardAction"</SPAN>
parameter=<SPAN class=java-quote>"/pages/Welcome.jsp"</SPAN>/>
<action
path=<SPAN class=java-quote>"/LoginAction"</SPAN>
type=<SPAN class=java-quote>"onlyfun.caterpillar.LoginAction"</SPAN>
name=<SPAN class=java-quote>"userForm"</SPAN>>
<forward
name=<SPAN class=java-quote>"greeting"</SPAN>
path=<SPAN class=java-quote>"/pages/greeting.jsp"</SPAN>/>
</action>
</action-mappings>
<message-resources parameter=<SPAN class=java-quote>"resources.application"</SPAN>/>
</struts-config></PRE></DIV></DIV><BR> 注意在<form-bean>的type屬性，我們設定使用
org.apache.struts.action.DynaActionForm，而Form的屬性則使用<form-property>
標籤來設定，DymaActionForm的type屬性希望得到的一個Java類別名稱，所以對於基本資料型態如int，必須以
java.lang.Integer作為Wrapper類別包裝。<BR> ActionForm類別的reset()方法預設什麼事都不作，除非您重新定義它，DynaActionForm則預設會將所有的資料重設為Java型態的預設值，例如數字重設為0，而Object則重設為null，您也可以使用initial屬性來設定重設的值。<BR> DynaActionForm同樣也被當作參數傳遞給execute()方法，DynaActionForm使用Map型態的方法來取值，下面的Action類別示範了如何取得DynaActionForm的屬性值：
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
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