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11.9 The errorPage Attribute

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11.9 The errorPage Attribute

The 

errorPage

 attribute specifies a JSP page that should process any excep 

tions (i.e., something of type 

Throwable

) thrown but not caught in the cur 

rent page. It is used as follows:

<%@ page errorPage="Relative URL" %>

The exception thrown will be automatically available to the designated

error page by means of the 

exception

 variable. See Listings 11.5 and 11.6

for examples.

11.10 The isErrorPage Attribute

The 

isErrorPage

 attribute indicates whether or not the current page can act

as the error page for another JSP page. Use of 

isErrorPage

 takes one of the

following two forms:

<%@ page isErrorPage="true" %> 

<%@ page isErrorPage="false" %> <%!   Default   %>

For example, Listing 11.5 shows a JSP page to compute speed based upon

distance and time parameters. The page neglects to check if the input param 

eters are missing or malformed, so an error could easily occur at run time.

However, the page designated 

SpeedErrors.jsp

 (Listing 11.6) as the page

to handle errors that occur in 

ComputeSpeed.jsp

, so the user does not

receive the typical terse JSP error messages. Figures 11 9 and 11 10 show

results when good and bad input parameters are received, respectively. 

Listing 11.5 ComputeSpeed.jsp