Often, the application will not be able to (Web server info)
Often, the application will not be able to recover from a RemoteException and will have to display the system error page. If you’re using EJB and you get a RemoteException, you can attempt to recover by acquiring a new remote reference, but there’s probably some type of programming or environment error that will prevent the end user from continuing. Whether you’re using a programmatic or a declarative approach, you’ll likely want to log the exception, create and store an ActionError object, and then forward to the system error page. You can also define the exception-handling behavior to forward the user back to the previous page and give her the choice of trying again. If some type of network blip caused the remote exception, it may be possible for the user to continue to use the application. 10.5.2 Exceptions in Custom Tags JSP custom tags usually throw JSPException objects or one of their descendants. Prior to the JavaServer Pages 1.2 specification, the JSPException class didn’t support exception chaining, and because Struts was introduced before the 1.2 specification, several places inside the Struts custom tag libraries still disregard the original exception when a JSPException is created. However, the Struts tags do usually store the exception in the request scope under the key Action.EXCEPTION_KEY, which maps to a literal string of org.apache.struts.action.Action.EXCEPTION_KEY. If you need to get access to the root cause, you can probably use this key to retrieve the exception object. Version 1.2 of the JSP specification modified the JSPException to support exception chaining; however, the Struts developers will probably choose to leave the current tags alone for backward compatibility and will take advantage of this new functionality only for future tags. However, in the custom tags that you create, you should use the rootCausefield in the JSPException class when you rethrow exceptions as different types. 10.5.2.1 The TryCatchFinally interface The JSP 1.2 specification also introduced a new interface called TryCatchFinally. This interface, which is referred to as a “mix-in” interface, can be implemented by a tag handler in addition to one of the other tag interfaces. The TryCatchFinally interface provides two methods: public void doCatch(Throwable); public void doFinally( ); The container calls the doCatch( )method if the tag body or one of the doStartEnd( ), doEndTag( ), doInitBody( ), or doAfterBody( )methods throws a Throwable. The doCatch( )method can rethrow the same or a different exception after handling the error. The container calls the doFinally( )method after the doEndTag( ) or after the doCatch( )method when an exception condition occurs. The TryCatchFinally interface allows for better exception handling in custom tags. It is very important to allow limited resources that are being used by custom tags to be released. Without this
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