Facelets自定义错误页面 - 自定义/包装异常消息/堆栈跟踪 [英] Facelets custom error page - customize / wrap the exception message / stack trace

问题描述

我正在使用JBoss AS7。
我已经知道如何使用我自己的 web.xml HTTP错误的错误页面（例如404,500，...） - 这不是问题。
但是为了调试原因，我需要查看StackTrace的错误。如何访问默认显示的消息并将其嵌入错误页面？

解决方案

具体异常实例可用一个请求属性，其名称由 RequestDispatcher＃ERROR_EXCEPTION ，其值为 javax.servlet.error.exception 。

因此，这将给你例外：

 ＃{requestScope ['javax.servlet.error.exception' ]} 
  

但是，在视图中没有打印其堆栈跟踪的标准功能。您需要自制一个EL功能，像 JSF实用程序库OmniFaces 已经具有＃{of：printStackTrace（）}的风格。您可以在 OmniFaces FullAjaxExceptionHandler 展示中看到它页面：

 < ui：composition ... xmlns：of =http://omnifaces.org /功能> 
 ... 
< li>堆栈跟踪：< pre>< code>＃{of：printStackTrace（requestScope ['javax.servlet.error.exception']）}< / code> ;< /预>< /锂> 
  

其功能实现如下所示：

  / ** 
 *打印给定异常的堆栈跟踪。 
 * @param exception打印堆栈跟踪的异常。 
 * @return打印的堆栈跟踪。 
 * / 
 public static String printStackTrace（Throwable exception）{
 if（exception == null）{
 return null; 
} 
 
 StringWriter stringWriter = new StringWriter（）; 
 exception.printStackTrace（new PrintWriter（stringWriter，true））; 
 return stringWriter.toString（）; 
} 
  

另请参见：

• 对AJAXified组件处理JSF 2.0异常的正确方法是什么？


• 从servlet转发到例外的好方法是什么？ jsp页面？

I am using JBoss AS7. I already know how to use my own web.xml error pages for HTTP Errors (e.g. 404, 500, ...) - thats not a problem. But for debugging reasons I need to view the error StackTrace. How can I access the message that is shown by default and embed it in error page?

解决方案

The concrete exception instance is available as a request attribute with the name as keyed by RequestDispatcher#ERROR_EXCEPTION which has a value of javax.servlet.error.exception.

Thus, this will give you the exception:

#{requestScope['javax.servlet.error.exception']}

However, there's no standard facility to print its stack trace in the view. You'd need to homebrew an EL function, something like as JSF utility library OmniFaces already has in flavor of #{of:printStackTrace()}. You can see it in action in the OmniFaces FullAjaxExceptionHandler showcase page:

<ui:composition ... xmlns:of="http://omnifaces.org/functions">
...
<li>Stack trace: <pre><code>#{of:printStackTrace(requestScope['javax.servlet.error.exception'])}</code></pre></li>

whereby the function implementation look like this:

/**
 * Print the stack trace of the given exception.
 * @param exception The exception to print the stack trace for.
 * @return The printed stack trace.
 */
public static String printStackTrace(Throwable exception) {
    if (exception == null) {
        return null;
    }

    StringWriter stringWriter = new StringWriter();
    exception.printStackTrace(new PrintWriter(stringWriter, true));
    return stringWriter.toString();
}

See also:

• What is the correct way to deal with JSF 2.0 exceptions for AJAXified components?
• What is the good approach to forward the exception from servlets to a jsp page?

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