cfcatch

Used inside a cftry tag. Together, they catch and process exceptions in ColdFusion pages. Exceptions are events that disrupt the normal flow of instructions in a ColdFusion page, such as failed database operations, missing include files, and developer-specified events.

Exception handling tags

<cfcatch type = "exceptiontype">
   Exception processing code here
</cfcatch>

cftry, cferror, cfrethrow, cfthrow, Handling Errors in Developing ColdFusion MX Applications

ColdFusion MX:

• Changed SQLSTATE value behavior: the SQLSTATE return value in a cfcatch tag depends on the database driver type:
• Type 1 (JDBC-ODBC bridge): the value is the same as in ColdFusion 5
• Type 4 (100% Java, no native methods): the value might be different

If your application depends on SQLSTATE values for flow control, the application might produce unexpected behavior with ColdFusion MX.

• Changed the behavior of this tag when type="any": it is not necessary, when you include a cfcatch tag with type="any", to do so in the last cfcatch tag in the block, to ensure that all other tests are executed before it. ColdFusion finds the best-match cfcatch block.
• Changed the behavior of the cfscript tag: it includes try and catch statements that are equivalent to the cftry and cfcatch tags.
• Changed object modification: you cannot modify the object returned by cfcatch.
• Changed thrown exceptions: the cfcollection, cfindex, and cfsearch tags can throw the SEARCHENGINE exception. In earlier releases, an error in processing these tags threw only an UNKNOWN exception.

You must code at least one cfcatch tag within a cftry block. Put cfcatch tags at the end of a cftry block. ColdFusion MX tests cfcatch tags in the order in which they appear. This tag requires an end tag.

If type="any", ColdFusion MX catches exceptions from any CFML tag, data source, or external object. To get the exception type use code such as the following:

   #cfcatch.type#

Applications can use the cfthrow tag to throw developer-defined exceptions. Catch these exceptions with any of these type options:

• "custom_type"
• "Application"
• "Any"

The custom_type type is a developer-defined type specified in a cfthrow tag. If you define a custom type as a series of strings concatenated by periods (for example, "MyApp.BusinessRuleException.InvalidAccount"), ColdFusion MX can catch the custom type by its character pattern. ColdFusion MX searches for a cfcatch tag in the cftry block with a matching exception type, starting with the most specific (the entire string), and ending with the least specific.

For example, you could define a type as follows:

<cfthrow type = "MyApp.BusinessRuleException.InvalidAccount">

If you have the following cfcatch tag, it will handle the exception:

<cfcatch type = "MyApp.BusinessRuleException.InvalidAccount"> 

Otherwise, if you have the following cfcatch tag, it will handle the exception:

<cfcatch type = "MyApp.BusinessRuleException"> 

Finally, if you have the following cfcatch tag, it will handle the exception:

<cfcatch type = "MyApp"> 

You can code cfcatch tags in any order to catch a custom exception type.

If you specify type = "Application", the cfcatch tag catches only custom exceptions that have the Application type in the cfthrow tag that defines them.

The cfinclude, cfmodule, and cferror tags throw an exception of type = "template".

An exception that is thrown within a cfcatch block cannot be handled by the cftry block that immediately encloses the cfcatch tag. However, you can rethrow the currently active exception with the cfrethrow tag.

The cfcatch variables provide the following exception information:

cfcatch.type

cfcatch.message 

cfcatch.detail 

cfcatch.tagcontext 

cfcatch.NativeErrorCode

cfcatch.SQLState

cfcatch.Sql

cfcatch.queryError

cfcatch.where

cfcatch.ErrNumber

cfcatch.MissingFileName 

cfcatch.LockName

cfcatch.LockOperation

cfcatch.ErrorCode

cfcatch.ExtendedInfo

Advanced Exception types

You can specify the following advanced exception types in the type attribute:

<!--- cftry example, using TagContext to display the tag stack. --->
<h3>cftry Example</h3>
<!--- open a cftry block --->
<cftry>
   <!--- note misspelled tablename "employees" as "employeeas" --->
   <cfquery name = "TestQuery" dataSource = "cfsnippets">
      SELECT *
      FROM EMPLOYEEAS
   </cfquery>

   <!--- <p>... other processing goes here --->
   <!--- specify the type of error for which we search --->
   <cfcatch type = "Database">
   <!--- the message to display --->
      <h3>You've Thrown a Database <b>Error</b></h3>
      <cfoutput>
         <!--- and the diagnostic message from the ColdFusion server --->
         <p>#cfcatch.message#</p>
         <p>Caught an exception, type = #CFCATCH.TYPE# </p>
         <p>The contents of the tag stack are:</p>
         <cfloop index = i from = 1 
               to = #ArrayLen(CFCATCH.TAGCONTEXT)#>
            <cfset sCurrent = #CFCATCH.TAGCONTEXT[i]#>
            <br>#i# #sCurrent["ID"]# 
               (#sCurrent["LINE"]#,#sCurrent["COLUMN"]#) 
               #sCurrent["TEMPLATE"]#
         </cfloop>
      </cfoutput>
   </cfcatch>
</cftry>

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