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Posted to dev@tapestry.apache.org by bu...@apache.org on 2015/12/22 06:19:42 UTC
svn commit: r976119 - in /websites/production/tapestry/content:
cache/main.pageCache overriding-exception-reporting.html
runtime-exceptions.html
Author: buildbot
Date: Tue Dec 22 05:19:42 2015
New Revision: 976119
Log:
Production update by buildbot for tapestry
Modified:
websites/production/tapestry/content/cache/main.pageCache
websites/production/tapestry/content/overriding-exception-reporting.html
websites/production/tapestry/content/runtime-exceptions.html
Modified: websites/production/tapestry/content/cache/main.pageCache
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Binary files - no diff available.
Modified: websites/production/tapestry/content/overriding-exception-reporting.html
==============================================================================
--- websites/production/tapestry/content/overriding-exception-reporting.html (original)
+++ websites/production/tapestry/content/overriding-exception-reporting.html Tue Dec 22 05:19:42 2015
@@ -131,7 +131,7 @@
</div>
</li></ul>
-</div><p>Of course, one of the first questions anyone asks is "How do I turn it off?" This exception reporting is very helpful for developers but its easy to see it as terrifying for potential users. Catching runtime exceptions can be a very useful way of handling rarely occurring exceptions even in production, and there's no reason to throw away Tapestry's default error reporting just to handle a few specific exceptions. From version 5.4 (for previous versions, the functionality is available as an external, third-party module tapestry-exceptionpage), you can contribute exception handles and/or exception pages for specific exception types. Refer back to <a href="runtime-exceptions.html">Runtime Exceptions</a> page for more information. Read on if you want to completely replace Tapestry's default exception handling.</p><h2 id="OverridingExceptionReporting-Version1:ReplacingtheExceptionReportPage">Version 1: Replacing the Exception Report Page</h2><p>Let's start with a page that fire
s an exception from an event handler method.</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>ActionFail.tml</b></div><div class="codeContent panelContent pdl">
+</div><p>Of course, one of the first questions anyone asks is "How do I turn it off?" This exception reporting is very helpful for developers but its easy to see it as terrifying for potential users. Catching runtime exceptions can be a very useful way of handling rarely occurring exceptions even in production, and there's no reason to throw away Tapestry's default error reporting just to handle a few specific exceptions. From version 5.4 (for previous versions, the same functionality is available as a <a class="external-link" href="http://www.tynamo.org/tapestry-exceptionpage+guide/" rel="nofollow">third-party module tapestry-exceptionpage</a>), you can contribute exception handles and/or exception pages for specific exception types. Refer back to <a href="runtime-exceptions.html">Runtime Exceptions</a> page for more information. Read on if you want to completely replace Tapestry's default exception handling.</p><h2 id="OverridingExceptionReporting-Version1:ReplacingtheExceptionR
eportPage">Version 1: Replacing the Exception Report Page</h2><p>Let's start with a page that fires an exception from an event handler method.</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>ActionFail.tml</b></div><div class="codeContent panelContent pdl">
<pre class="brush: xml; gutter: false; theme: Default" style="font-size:12px;"> <html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_4.xsd" t:type="layout" title="Action Fail">
<p>
<t:actionlink t:id="fail" class="btn btn-large btn-warning">Click for Exception</t:actionlink>
Modified: websites/production/tapestry/content/runtime-exceptions.html
==============================================================================
--- websites/production/tapestry/content/runtime-exceptions.html (original)
+++ websites/production/tapestry/content/runtime-exceptions.html Tue Dec 22 05:19:42 2015
@@ -59,7 +59,7 @@
</div>
<div id="content">
- <div id="ConfluenceContent"><p>Feedback is vitally important when developing an application, and that is one of the areas where Tapestry has always exceled.</p><p>Especially during development, requests can fail. There can be errors in templates, broken code in your application, or something unexpected.</p><p>Tapestry has a built-in exception report page that captures an amazing wealth of information:</p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" width="500" src="runtime-exceptions.data/Exception%20-%20Stack%20Trace%20.png"></span></p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" width="500" src="runtime-exceptions.data/Exception%20-%20Request.png"></span></p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="co
nfluence-embedded-image confluence-content-image-border" height="443" width="500" src="runtime-exceptions.data/Application_Exception.png"></span></p><p>This exception report features:</p><ul><li>The full stack of exceptions, top to bottom.</li><li>All non-null properties of each exception.</li><li>The stack trace <em>at the deepest level</em>.</li><li>Key <strong>request</strong> properties, header, attributes, and parameters.</li><li>Key <strong>session</strong><em> </em>propertes</li><li>A break down of the <em>thread</em> in your application</li><li>A listing of all JVM System properties<br clear="none"><br clear="none"></li></ul><p>In addition, Tapestry will write a text file for the exception with a similar level of detail.</p><p>In production you will want to <a href="overriding-exception-reporting.html">override the exception report page</a> (but will likely keep the text file output).</p><p>This exception report is also built-in to Tapestry's Ajax s
upport. When an Ajax request fails, Tapestry's client-side code will create an <iframe> to present this same information:</p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" height="359" width="500" src="runtime-exceptions.data/Exception%20-%20Ajax.png"></span></p><p> </p></div>
+ <div id="ConfluenceContent"><p>Feedback is vitally important when developing an application, and that is one of the areas where Tapestry has always excelled.</p><p>Especially during development, requests can fail. There can be errors in templates, broken code in your application, or something unexpected.</p><p>Tapestry has a built-in exception report page that captures an amazing wealth of information:</p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" width="500" src="runtime-exceptions.data/Exception%20-%20Stack%20Trace%20.png"></span></p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" width="500" src="runtime-exceptions.data/Exception%20-%20Request.png"></span></p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="c
onfluence-embedded-image confluence-content-image-border" height="443" width="500" src="runtime-exceptions.data/Application_Exception.png"></span></p><p>This exception report features:</p><ul><li>The full stack of exceptions, top to bottom.</li><li>All non-null properties of each exception.</li><li>The stack trace <em>at the deepest level</em>.</li><li>Key <strong>request</strong> properties, header, attributes, and parameters.</li><li>Key <strong>session</strong><em> </em>propertes</li><li>A break down of the <em>thread</em> in your application</li><li>A listing of all JVM System properties<br clear="none"><br clear="none"></li></ul><p>In addition, Tapestry will write a text file for the exception with a similar level of detail.</p><p>This exception report is also built-in to Tapestry's Ajax support. When an Ajax request fails, Tapestry's client-side code will create an <iframe> to present this same information:</p><p><span class="confluence-embedded-
file-wrapper confluence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" height="359" width="500" src="runtime-exceptions.data/Exception%20-%20Ajax.png"></span></p><p>In production, you may want to <a href="overriding-exception-reporting.html">override the exception report page</a> (but will likely keep the text file output). However, Tapestry's (from version 5.4) default exception reporter also allows you to handle specific exception types in a pre-determined manner, similar to how servlet spec's standard error-page/exception-type configuration option allows you to map exception types to URLs. At times, it's simpler to just catch exceptions at the outermost layer of your application instead of carrying a typed exception through multiple layers of abstractions just so you could show a sensible error message to the user, especially if you can't do anything more clever about it anyway. Exception type mapping in Tapestry is much more powerfu
l than what the servlet spec dictates. If your email service or an external payment service goes down, you can't do much more than display an error message to the user, so why would you need to implement separate pages for each exception? Often, it'd be nicer if you could just reuse the page template for any fatal exception and simply display a different error message. In addition to contributing handlers for specific types of exceptions, you may also provide context for rendering the same error page template with a different output.</p><p> </p><p>You can contribute an error page, mapping it to an exception type:</p><p>    public void contributeExceptionHandler(MappedConfiguration<Class, Class> configuration) {</p><p>        configuration.add(SmtpNotRespondingException.class, ServiceFailure.class);</p><p>    }</p><p> </p><p>If a simple exception type to page mapping doesn't do it for you, you can also contri
bute a custom handler for that particular exception type. An ExceptionHandlerAssistant can contain arbitrarily complex logic for handling a specific exception type and use other Tapestry services. If ExceptionHandlerAssistant.handleRequestException(Throwable exception, List<Object> exceptionContext) returns an Object representing an URL the main handler will issue a redirect to that URL. It's valid to return either a String, a Link or a Class; the last case implies a page class. If the ExceptionHandlerAssistant returns null, it's assumed that the assistant has independently handled the exception. You can either contribute an instance of an ExceptionHandlerAssistant or a class that implements ExceptionHandlerAssistant. Below, we contribute an instance handling ServiceExceptions:</p><p>    public void contributeExceptionHandler(OperationQueue operationQueue, MappedConfiguration<Class, Class> configuration) {</p><p>        final
ExceptionHandlerAssistant assistant = new ExceptionHandlerAssistant() {</p><p>        @Override</p><p>        public Object handleRequestException(Throwable exception, List<Object> exceptionContext) throws IOException {</p><p>          ServiceException serviceException = (ServiceException)exception;</p><p>          if (serviceException.isInterruptedOperationRecoverable()) {</p><p>              operationQueue.add(serviceException.getInterruptedOperation());</p><p>              return OperationScheduled.class;</p><p>          }</p><p>          else return ServiceUnavailable.class;</p><p>        }</p><p>    
0;   };</p><p>        configuration.add(ServiceException.class, assistant);</p><p>    }</p><p> </p><p>You can also specify context for the exception page. For generic exceptions, the context is taken from the exception class name minus the word "Exception" in case that's how the class name ends. For example, you have a following class:</p><p> </p><p>    public class SmtpNotRespondingException extends RuntimeException {</p><p>        ...</p><p>    }</p><p> </p><p>If an SmtpNotRespondingException is thrown during an action request, user is directed to ServiceFailure page with a String context smtpnotresponding (i.e. to URL **/servicefailure/smtpnotresponding**). Tapestry-exceptionpage works both for regular action requests and ajax action requests. In the latter case, the module will use Javascript to redirect to the error page. If the exception thrown wasn
't an explicitly specified exception type (i.e. a contributed type), handling is delegated back to the default Tapestry exception handler.</p><p>If your custom-handled exception implements the interface *ContextAwareException* you can fully specify the context for the error page. For example, you could implement a following Exception class:</p><p>    public class SmtpNotRespondingException extends RuntimeException implements ContextAwareException {</p><p>        private Object[] context;  </p><p>        public EmailServiceException(Object[] context) {</p><p>            super();</p><p>            this.context = context;</p><p>        }</p><p>        // Defined in ContextAwareException interface</p><p>        public Object[]
getContext() {</p><p>            return context;</p><p>        }</p><p>    }</p><p> </p><p>This exception handling mechanism can easily be overused. Typically, if you can handle the exception locally, you should. Likewise, you shouldn't blindly wrap any checked exceptions inside runtime exceptions just to avoid writing try-catch blocks in higher layers. The exceptionpage module is best used for handling serious but rarely occurring exceptions happening in the action request cycle that you cannot otherwise cope with.</p></div>
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