📄 入門 12 - struts例外處理 - javaworld@tw.htm
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HttpServletRequest request,
HttpServletResponse response)
<SPAN class=java-keyword>throws</SPAN> ServletException {
....
}</PRE></DIV></DIV><BR> 如果您想要自行處理被丟出的例外，您可以繼承ExceptionHandler並重新定義execute()方法，並在<exception>標籤中使用屬性handler指定您自訂的ExceptionHandler類別：
<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><global-exceptions>
<exception
key=<SPAN class=java-quote>"expired.password"</SPAN>
type=<SPAN class=java-quote>"app.ExpiredPasswordException"</SPAN>
handler=<SPAN class=java-quote>"onlyfun.caterpillar.CustomExceptionHandler"</SPAN>
path=<SPAN class=java-quote>"/changePassword.jsp"</SPAN>/>
</global-exceptions></PRE></DIV></DIV><BR> 如果您想要深入瞭解Struts的例外處理方式，可以看看RequestProcessor原始碼中的processException()方法，以及ExceptionHandler的execute()方法。<BR> 當Action物件丟出例外時，RequestProcessor的processException()方法會看看是否有在<
exception>標籤中聲明，這個工作是委由ActionMapping物件的findException()方法來執行，如果找不到相對應的例外處理，除了標籤中聲明，這個工作是委由ActionMapping物件的findException()方法來執行，如果找不到相對應的例外處理，除了IOException直接丟出之外，其它的例外則將之包裝為ServletException例外再丟出：
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<DIV class=codeContent><PRE>ExceptionConfig config = mapping.findException(exception.getClass());
<SPAN class=java-keyword>if</SPAN>(config == <SPAN class=java-keyword>null</SPAN>) {
....
<SPAN class=java-keyword>if</SPAN>(exception <SPAN class=java-keyword>instanceof</SPAN> IOException) {
<SPAN class=java-keyword>throws</SPAN> (IOException) exception;
}
<SPAN class=java-keyword>else</SPAN> <SPAN class=java-keyword>if</SPAN>(exception <SPAN class=java-keyword>instanceof</SPAN> ServletException) {
<SPAN class=java-keyword>throws</SPAN> (ServletException) exception;
}
<SPAN class=java-keyword>else</SPAN> {
<SPAN class=java-keyword>throws</SPAN> <SPAN class=java-keyword>new</SPAN> ServletException(exception);
}
}</PRE></DIV></DIV><BR> 如果RequestProcessor的processException()找到對應的例外處理，則載入ExceptionHandler進行處理，最後返回一個ActionForward物件：
<DIV class=code
style="BORDER-TOP-STYLE: solid; BORDER-RIGHT-STYLE: solid; BORDER-LEFT-STYLE: solid; BORDER-BOTTOM-STYLE: solid">
<DIV class=codeContent><PRE><SPAN class=java-object>Class</SPAN> handlerClass = <SPAN class=java-object>Class</SPAN>.forName(config.getHandler());
ExceptionHandler handler = (ExceptionHandler) handlerClass.newInstance();
<SPAN class=java-keyword>return</SPAN> (handler.execute(exception, config, mapping, form, request, response));</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=522" dc:identifier="http://www.javaworld.com.tw/confluence/pages/viewpage.action?pageId=522" dc:title="入門 12 - Struts例外處理" trackback:ping="http://www.javaworld.com.tw/confluence/rpc/trackback/522"/></rdf:RDF>-->
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