Adobe 38043740 Developing Applications - Page 282

DEVELOPING COLDFUSION 9 APPLICATIONS 277 Developing CFML Applications Type Exception Missing template Form field data validation Description An error that prevents normal processing from continuing. All ColdFusion exceptions are, at their root, Java exceptions. An HTTP request for a ColdFusion page that cannot be found. Generated if a browser requests a ColdFusion page that does not exist. Missing template errors are different from missing include exceptions, which result from cfinclude tags or custom tag calls that cannot find their targets. Server-side form field validation errors are a special kind of ColdFusion exception. You specify serverside form validation by using cfform attributes or hidden HTML form fields. All other types of serverside validation, such as the cfparam tag generate runtime exceptions. For more information on validating form fields see "Validating Data" on page 743. ColdFusion includes a built-in error page for server-side form field validation errors, and the cferror tag includes a type attribute that lets you handle these errors in a custom error page, but if you use onError processing in Application.cfc, or try/catch error handling, the error appears as an Application exception. For more information on handling Form field validation in Application.cfc see "Handling server-side validation errors in the onError method" on page 248. Note: The onSubmit and onBlur form field validation techniques use JavaScript or Flash validation on the client browser. About ColdFusion exceptions Most ColdFusion errors are exceptions. You can categorize ColdFusion exceptions in two ways: • When they occur • Their type When exceptions occur ColdFusion errors can occur at two times, when the CFML is compiled into Java and when the resulting Java executes, called runtime exceptions. Compiler exceptions Compiler exceptions are programming errors that ColdFusion identifies when it compiles CFML into Java. Because compiler exceptions occur before the ColdFusion page is converted to executable code, you cannot handle them on the page that causes them. However, other pages can handle these errors. For more information, see "Handling compiler exceptions" on page 282. Runtime exception A runtime exception occurs when the compiled ColdFusion Java code runs. It is an event that disrupts the normal flow of instructions in the application. Exceptions can result from system errors or program logic errors. Runtime exceptions include: • Error responses from external services, such as an ODBC driver or CORBA server • CFML errors or the results of cfthrow or cfabort tags • Internal errors in ColdFusion Last updated 1/20/2012