Exceptions in Struts are handled in two ways:
Programmatic exception handling :
Explicit try/catch blocks in any code that can throw exception. It works well when custom value (i.e., of variable) needed when error occurs.
Declarative exception handling :You can either define <global-exceptions> handling tags in your struts-config.xml or define the exception handling tags within <action></action> tag. It works well when custom page needed when error occurs. This approach applies only to exceptions thrown by Actions.