CODEWITHSUNDEEP
jakarta-eeexceptionstrutsstruts-1
Supereme
Supereme

Reputation: 2409

How to handle exceptions in Struts?

I am new to Struts and currently working on 1.3.8 version of it. Please give me a simple example of handling exceptions in it using in struts-confg.xml file.

Thanks

Upvotes: 1

Views: 6887

Answers (1)

Jwalin Shah
Jwalin Shah

Reputation: 2521

Pls. check http://livingtao.blogspot.com/2007/05/global-exception-handling-for-struts.html this link or

New Solution

I abandoned the global-exceptions approach in struts-config altogether and added a section to the web.xml file which instructed the app server to forward the request to the specified URL on all unhandled exceptions.

<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>/error</location>
</error-page>

Then added a servlet and a servlet mapping to the /error URL

<servlet> 
<servlet-name>exceptionHandler</servlet-name> 
<servlet-class>com.test.ExceptionHandlerServlet</servlet-class> 
<init-param> 
<param-name>errorPageURL</param-name> 
<param-value>error.html</param-value> 
</init-param> 
<load-on-startup>3</load-on-startup> 
</servlet>


<servlet-mapping>
<servlet-name>exceptionHandler</servlet-name> 
<url-pattern>/error</url-pattern> 
 </servlet-mapping>

The ExceptionHandlerServlet would log the exception and redirect the browser to the URL defined in the servlet configuration (error.html).

ExceptionHandlerServlet Code:

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
logger.debug("Handling exception in ErrorHandlerServlet");

Throwable exception = null;

// Check if struts has placed an exception object in request
Object obj = request.getAttribute(Globals.EXCEPTION_KEY);

if (obj == null) {
// Since no struts exception is found,
// check if a JSP exception is available in request.
obj = request.getAttribute("javax.servlet.jsp.jspException");
}

if ((obj != null) && (obj instanceof Throwable)) {
exception = (Throwable) obj;
}

if (logger.isDebugEnabled()) {
logger.debug("Request URI: " + request.getAttribute("javax.servlet.forward.request_uri"));
}

// request uri containing the original URL value will be available
// only on servers implementing servlet 2.4 spec
String requestURI = (String) request.getAttribute("javax.servlet.forward.request_uri");

logger.error("Exception while handling request: " + requestURI, exception);
response.sendRedirect(errorPageURL);
} catch (Exception e) {
// Throwing exceptions from this method can result in request
// going in to an infinite loop forwarding to the error servlet recursively.
e.printStackTrace();
}
}

Now on all unhandled exceptions the servlet will log the exception. Yet on some occasions where the exception was thrown in one of the tile JSPs the browser would display a partially rendered page and would not redirect to the error page.

This was due to tiles flushing content to the response buffer before the whole page was rendered. In such a situation the browser will happily display what it received and the redirect to the error page will have no effect.

In order to prevent or minimize the flushing of response buffer:

  1. Set flush attribute to false in all tiles insert tags
  2. Increase the response buffer size to minimize auto flushing

This was achieved by modifying the tiles layout jsp page.

<!-- sets the response buffer size to 64kb -->
<%@ page buffer="64kb"%>
<%@ taglib uri="/WEB-INF/struts-tiles.tld" prefix="tiles"%>
…
<tiles:insert attribute="header" flush="false" />
<tiles:insert attribute="leftnav" flush="false" />
<tiles:insert attribute="body" flush="false" />
<tiles:insert attribute="footer" flush="false" />

In the above code segment all html formatting was removed for clarity. The response buffer was set to 64 kilobytes and this value should be decide based on the average page size of the application and the performance impact of the increased memory usage.

Upvotes: 2

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