MACROMEDIA COLDFUSION MX 61-DEVELOPING COLDFUSION MX, Develop Manual

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398 Chapter 18: Debugging and Troubleshooting Applications
The exception information includes information about any application exceptions that are caught
and handled by your application code or by ColdFusion MX.
Exceptions represent events that disrupt the normal flow of an application. You should catch and,
whenever possible, recover from forseeable exceptions in your application, as described in
Chapter
14, “Handling Errors,” on page 285 . However, you might also want to be alerted to caught
exceptions when you are debugging your application. For example, if a file is missing, your
application can catch the
cffile
exception and use a backup or default file instead. If you enable
exception information in the debugging output, you can immediately see when this happens.
Trace points
In the Administrator, when Tracing Information is selected on the Debugging Settings page, the
debugging output includes the results of all
cftrace
tags, including all tags that display their
results in-line. Therefore, the debugging output contains a historical record of all trace points
encountered in processing the request. This section looks like the following figure when you use
the classic.cfm output format:
For more information on using the
cftrace
tag, see “Using the cftrace tag to trace execution”
on page 401 .
Scope variables
In the Administrator, when the Variables option and one or more variable scopes are selected on
the Debugging Settings page, the debugging output displays the values of all variables in the
selected scopes. The debugging output displays the values that result after all processing of the
current page.
By displaying selected scope variables you can determine the effects of processing on persistent
scope variables, such as application variables. This can help you locate problems that do not
generate exceptions.
The Form, URL, and CGI scopes are useful for inspecting the state of a request. They let you
inspect parameters that affect page behavior, as follows:
•
URL variables
Identify the HTTP request parameters.
•
Form variables Identify the form fields posted to an action page.
•
CGI variables
Provide a view of the server environment following the request.
Similarly, the Client, Session, Application, and Server scope variables show the global state of the
application, and can be useful in tracing how each page affects the state of the ColdFusion
persistent variables.