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Posted to dev@tapestry.apache.org by bu...@apache.org on 2015/12/24 06:19:40 UTC
svn commit: r976267 - in /websites/production/tapestry/content:
cache/main.pageCache runtime-exceptions.html
Author: buildbot
Date: Thu Dec 24 05:19:40 2015
New Revision: 976267
Log:
Production update by buildbot for tapestry
Modified:
websites/production/tapestry/content/cache/main.pageCache
websites/production/tapestry/content/runtime-exceptions.html
Modified: websites/production/tapestry/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.
Modified: websites/production/tapestry/content/runtime-exceptions.html
==============================================================================
--- websites/production/tapestry/content/runtime-exceptions.html (original)
+++ websites/production/tapestry/content/runtime-exceptions.html Thu Dec 24 05:19:40 2015
@@ -27,6 +27,14 @@
</title>
<link type="text/css" rel="stylesheet" href="/resources/space.css" />
+ <link href='/resources/highlighter/styles/shCoreCXF.css' rel='stylesheet' type='text/css' />
+ <link href='/resources/highlighter/styles/shThemeCXF.css' rel='stylesheet' type='text/css' />
+ <script src='/resources/highlighter/scripts/shCore.js' type='text/javascript'></script>
+ <script src='/resources/highlighter/scripts/shBrushJava.js' type='text/javascript'></script>
+ <script>
+ SyntaxHighlighter.defaults['toolbar'] = false;
+ SyntaxHighlighter.all();
+ </script>
<link href="/styles/style.css" rel="stylesheet" type="text/css"/>
@@ -59,7 +67,43 @@
</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 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_Stack_Trace.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_Request.png"></span></p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedde
d-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 conf
luence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" height="359" width="500" src="runtime-exceptions.data/Exception_Ajax.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 powerful 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 contribute a custom handler f
or 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 ExceptionHandlerAssista
nt 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>        };</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 specif
ied 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>&
#160;           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>
+ <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_Stack_Trace.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_Request.png"></span></p><p><span class="confluence-embedded-file-wrapper confluence-embedded-manual-size"><img class="confluence-embedde
d-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 conf
luence-embedded-manual-size"><img class="confluence-embedded-image confluence-content-image-border" height="359" width="500" src="runtime-exceptions.data/Exception_Ajax.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 powerful 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>You can contribute an error page, mapping it to an exception type:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
+<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> public void contributeExceptionHandler(MappedConfiguration<Class, Class> configuration) {
+ configuration.add(SmtpNotRespondingException.class, ServiceFailure.class);
+ }</pre>
+</div></div><p>If a simple exception type to page mapping doesn't do it for you, you can also contribute a custom handler for that particular exception type. An <em>ExceptionHandlerAssistant</em> can contain arbitrarily complex logic for handling a specific exception type and use other Tapestry services. If <em>ExceptionHandlerAssistant.handleRequestException(Throwable exception, List<Object> exceptionContext)</em> 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 <em>ExceptionHandlerAssistant</em> returns null, it's assumed that the assistant has independently handled the exception. You can either contribute an instance of an <em>ExceptionHandlerAssistant</em> or a class that implements <em>ExceptionHandlerAssistant</em>. Below, we contribute an instance handling <em>ServiceException</em>s:</p><div class="code panel pdl" style="border-wid
th: 1px;"><div class="codeContent panelContent pdl">
+<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> public void contributeExceptionHandler(OperationQueue
+operationQueue, MappedConfiguration<Class, Class> configuration) {
+ final ExceptionHandlerAssistant assistant = new ExceptionHandlerAssistant() {
+ @Override
+ public Object handleRequestException(Throwable exception, List<Object> exceptionContext) throws IOException {
+ ServiceException serviceException = (ServiceException)exception;
+ if (serviceException.isInterruptedOperationRecoverable()) {
+ operationQueue.add(serviceException.getInterruptedOperation());
+ return OperationScheduled.class;
+ }
+ else return ServiceUnavailable.class;
+ }
+ };
+ configuration.add(ServiceException.class, assistant);
+ }</pre>
+</div></div><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><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
+<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">public class SmtpNotRespondingException extends RuntimeException {
+ ...
+}</pre>
+</div></div><p>If an <em>SmtpNotRespondingException</em> is thrown during an action request, user is directed to <em>ServiceFailure</em> page with a String context smtpnotresponding (i.e. to URL <strong>/servicefailure/smtpnotresponding</strong>). The contributed exception handling 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 is not one of the contributed types, the exception is handled like any other exception, as explained above.</p><p>If your custom-handled exception implements the interface <em>org.apache.tapestry5.ContextAwareException</em> you can fully specify the context for the error page. For example, you could implement a following Exception class:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
+<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> public class SmtpNotRespondingException extends RuntimeException implements ContextAwareException {
+ private Object[] context;
+ public EmailServiceException(Object[] context) {
+ super();
+ this.context = context;
+ }
+ // Defined in ContextAwareException interface
+ public Object[] getContext() {
+ return context;
+ }
+ }</pre>
+</div></div><p>The contributed 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 mechanism for contributed exception types is best used for handling serious but rarely occurring exceptions happening in the action request cycle that you cannot otherwise cope with.</p></div>
</div>
<div class="clearer"></div>