Addison wesley servlets and javaserver pages the J2EE technology web tier sep 2003 ISBN 0321136497

FinishingtheSite
Beforemovingon,thereareafewbitsandpiecesofthesitethatneedtobe
addressed.Thebulkofthesiteconsistsofthecustomcomponentspreviously
addressedbythischapter.Allofthecustomcomponentsrequiredcodingfrom
scratch.Nowweshalladdressseveralcomplementarycomponentsthatwere
demonstratedinpreviouschapters.Allthecomponentswillberelativelysimple
toimplement;insteadofcodingfromscratch,wewillsimplydeploypreviously
explainedcodelistings.
Thelistofthingstoimplementisasfollows:site-wideerrorhandling,security,
linktracking,caching,compression,andthesite'shiddenEasteregg.Eachofthe
componentswascompletelycoveredinpreviouschapters,buteachcomponent
isbrieflyrehashedinthefollowingsectionsasitisinstalledforusewiththe
booksupportsite.
Site-WideErrorHandling
Allofthecodepreviouslyprovidedforthebooksupportsiteusespropererror
handling;however,anerrorcanstillbethrown(althoughitprobablyneverwill)
bytheWebApplication.Shouldthishappen,thecontainerwillhavetohandle
theerror.Normally,aswithTomcat,astacktraceisprintedanddisplayedina
developer-friendlyfashion,meaningacrypticpageisshowntoauser.To
preventthisfromhappening,weneedtocreateaWebApplicationerrorpage.
You'llrecallinChapter4thatthistopicwasdiscussedatlength.Theerrorpage
needstobenothingmorethanasimpleJSPorServletthatisregisteredvia
web.xml.
Listing15-35showsasimpleerrorpage.
Listing15-35.error.jsp

[Viewfullwidth]

Oops!

Anerrorhasoccurred.Informationabouttheproblemhasbeen
loggedandwillbehandledbyadministratorsassoonaspossible.If

youwouldliketosendfurtherinformation,pleasecontact.com">support</a>.

Thepagedoesn'tdoanythingfancy.Itapologeticallyinformsauserthatthesite
hasfailedtofunctioncorrectly.Additionally,anemailaddressisprovidedin
casetheuserwishestocommunicatefurtherabouttheproblem.
Saveerror.jspintherootdirectoryofthejspbook_siteWebApplication.
Deploythepageasthesite'sdefaulterrorpagebyaddingListing15-36to
web.xml.
Listing15-36.Settingerror.jspastheSite'sDefaultErrorPage

<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>/error.jsp</location>
</error-page>

ReloadtheWebApplicationforthechangestotakeeffect.NowwehaveafailsafecountertoTomcat'sdisplayingacrypticstacktracetouse.Althoughit
shouldneverhappen,planfortheworst.Youcantestthepagebybrowsing
http://127.0.0.1/jspbook_site/error.jsp.Thepageprovidesapoliteerror
messageandisrenderedwiththesite'simplicitheaderandfooter.Figure15-18
providesabrowserrenderingoftheresultsinEnglish.
Figure15-18.BrowserRenderingofthePoliteErrorPage