Beginning Web Development With Perl : From Novice to ... - Nabo

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CHAPTER 12 ■ THE TEMPLATE TOOLKIT 253The variable was neither true nor false.[% END %]Notice that within the IF and ELSIF sections, the equality test is two equals signs separatedby a space:= =This is different from Perl-ish equality testing, which is either eq or two equals signs withno space between them:==The UNLESS conditional is used like its Perl counterpart, as follows:[% UNLESS variable = = "true" %]SWITCH and CASEAlso like Perl, SWITCH and CASE type conditionals are available, though technically SWITCH isnot native in Perl, but rather is part of the switch module (though it will be standard in Perl 6).With this much commonality between Perl and the template language, you can see that if youknow Perl, it should be easy to make the leap to the Template Toolkit language.[% SWITCH searchengine %][% CASE "google" %]Google was chosen.[% CASE "yahoo" %]Yahoo was chosen.[% CASE %]No choice was made[% END %]Notice that the last CASE statement contained no value for the variable. This is the defaultcase if no others match.Exception HandlingException handling and error catching is necessary when working with templates, just as it iswhen working with Perl. This is because templates can get quite complex, incorporating connectionsto databases and external files and programs. The Template Toolkit provides TRY-CATCHblocks to trap errors within template code.The TRY directive introduces a template and other information for processing. The TRYdirective continues processing until a corresponding END is encountered. If an error occurs,the code within the CATCH block is executed. Consider the example in Listing 12-6.Listing 12-6. TRY-CATCH Block[% TRY %]This code doesn't do much except maybe fail.[% CALL othercode %][% INCLUDE sometemplatefile %]
254CHAPTER 12 ■ THE TEMPLATE TOOLKIT[% CATCH %]Error: [% error.type %]: [% error.info %][% END %]Along with some leading and trailing blank lines (not shown), the output from this exampleis as follows:This code doesn't do much except maybe fail.Error: file: sometemplatefile: not foundAs you can see in the preceding example, a special object called error is created withinthe CATCH block. This error object has two properties, type and info, both of which are printed.You can use the error type to perform more granular exception handling. Listing 12-7 showsthe file type error being caught.Listing 12-7. Adding the Error Type to the CATCH Block[% TRY %]This code doesn't do much except maybe fail.[% CALL othercode %][% INCLUDE sometemplatefile %][% CATCH file %]File Error: [% error.info %][% CATCH %]Error: [% error.type %]: [% error.info %][% END %]The output from Listing 12-7 is as follows:This code doesn't do much except maybe fail.File Error: sometemplatefile: not foundThe code sample used two new items. First, the type of error was checked and caught if itwas a file type (as would be reported by error.type), and a default CATCH block was also created.One additional feature of the TRY-CATCH syntax is a FINAL block. Content and code withina FINAL block get processed regardless of what happens within the TRY-CATCH blocks. This canbe helpful for printing footer or other information that’s necessary for the template you’re processing.Blocks of PerlAs if all of the power of template processing with Template Toolkit shown already isn’t enough,you can also execute blocks of pure Perl code within a template by defining the code withina PERL block inside of the template. The following example shows a Perl block in action:[% PERL -%]print "Hello, this is Perl!\n";[% END -%]
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Beginning Web Development with Perl
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PART 5 ■ ■ ■ Creating Web Tem
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■CONTENTSvii■CHAPTER 4 System I
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■CONTENTSixCreating a SOAP Listen
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■CONTENTSxiTemplate Toolkit Synta
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About the Author■STEVE SUEHRING i
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AcknowledgmentsThanks to James Lee
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xx■INTRODUCTIONThis book will use
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CHAPTER 1■ ■ ■The CGI ModuleT
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CHAPTER 1 ■ THE CGI MODULE 5for t
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CHAPTER 1 ■ THE CGI MODULE 7Obvio
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CHAPTER 1 ■ THE CGI MODULE 9exit;
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CHAPTER 1 ■ THE CGI MODULE 11Each
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CHAPTER 1 ■ THE CGI MODULE 13When
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CHAPTER 1 ■ THE CGI MODULE 15Upda
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CHAPTER 1 ■ THE CGI MODULE 17rese
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CHAPTER 1 ■ THE CGI MODULE 19prin
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CHAPTER 1 ■ THE CGI MODULE 21Sett
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CHAPTER 1 ■ THE CGI MODULE 23You
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CHAPTER 1 ■ THE CGI MODULE 25■C
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CHAPTER 1 ■ THE CGI MODULE 27No m
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CHAPTER 1 ■ THE CGI MODULE 29The
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CHAPTER 1 ■ THE CGI MODULE 31prin
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CHAPTER 1 ■ THE CGI MODULE 33Also
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CHAPTER 2■ ■ ■Popular CGI Mod
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CHAPTER 2 ■ POPULAR CGI MODULES 3
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50CHAPTER 3 ■ DATABASES AND PERLT
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52CHAPTER 3 ■ DATABASES AND PERLm
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54CHAPTER 3 ■ DATABASES AND PERLl
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56CHAPTER 3 ■ DATABASES AND PERLc
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58CHAPTER 3 ■ DATABASES AND PERLR
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62CHAPTER 3 ■ DATABASES AND PERLw
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64CHAPTER 3 ■ DATABASES AND PERLA
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74CHAPTER 4 ■ SYSTEM INTERACTION
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76CHAPTER 4 ■ SYSTEM INTERACTIONt
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78CHAPTER 4 ■ SYSTEM INTERACTIONc
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80CHAPTER 4 ■ SYSTEM INTERACTIONA
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82CHAPTER 4 ■ SYSTEM INTERACTIONm
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84CHAPTER 4 ■ SYSTEM INTERACTIONs
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86CHAPTER 4 ■ SYSTEM INTERACTIONr
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CHAPTER 5■ ■ ■LWP ModulesLWP
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CHAPTER 5 ■ LWP MODULES 91HTTP Re
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CHAPTER 5 ■ LWP MODULES 93Get Fun
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CHAPTER 5 ■ LWP MODULES 95When ca
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CHAPTER 5 ■ LWP MODULES 97These a
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CHAPTER 5 ■ LWP MODULES 99Recall
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CHAPTER 5 ■ LWP MODULES 101which
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CHAPTER 5 ■ LWP MODULES 103For th
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CHAPTER 5 ■ LWP MODULES 105Obviou
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108CHAPTER 6 ■ NET:: TOOLSCreatin
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110CHAPTER 6 ■ NET:: TOOLSThe out
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112CHAPTER 6 ■ NET:: TOOLSmy $pop
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114CHAPTER 6 ■ NET:: TOOLSthe POP
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116CHAPTER 6 ■ NET:: TOOLS($messa
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118CHAPTER 6 ■ NET:: TOOLSListing
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120CHAPTER 6 ■ NET:: TOOLSFor the
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122CHAPTER 6 ■ NET:: TOOLSNet::SM
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124CHAPTER 6 ■ NET:: TOOLS$smtpco
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126CHAPTER 6 ■ NET:: TOOLSuse Net
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128CHAPTER 6 ■ NET:: TOOLSListing
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130CHAPTER 6 ■ NET:: TOOLSFor exa
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132CHAPTER 6 ■ NET:: TOOLSSending
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PART 3■ ■ ■XML and RSS
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138CHAPTER 7 ■ SOAP-BASED WEB SER
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154CHAPTER 8 ■ PERL AND RSSFigure
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156CHAPTER 8 ■ PERL AND RSShttp:/
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158CHAPTER 8 ■ PERL AND RSSDebugg
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160CHAPTER 8 ■ PERL AND RSS$rsswr
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162CHAPTER 8 ■ PERL AND RSSListin
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CHAPTER 9■ ■ ■XML Parsing wit
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CHAPTER 9 ■ XML PARSING WITH PERL
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PART 4■ ■ ■PerformanceEnhance
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184CHAPTER 10 ■ APACHE AND MOD_PE
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Page 212 and 213: 202CHAPTER 11 ■ DEVELOPMENT WITH
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Page 292 and 293: 284APPENDIX ■ PERL BASICSKeywords
Page 294 and 295: 286APPENDIX ■ PERL BASICS$ perl n
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304APPENDIX ■ PERL BASICS$ perl s
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306APPENDIX ■ PERL BASICSThis cod
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308APPENDIX ■ PERL BASICS$a = 6 *
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310APPENDIX ■ PERL BASICS$a = "A9
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312APPENDIX ■ PERL BASICS#!/usr/b
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314APPENDIX ■ PERL BASICSmy $name
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316APPENDIX ■ PERL BASICSis short
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318APPENDIX ■ PERL BASICSLet’s
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320APPENDIX ■ PERL BASICSOther Te
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322APPENDIX ■ PERL BASICS}}}actio
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324APPENDIX ■ PERL BASICSNotice t
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326APPENDIX ■ PERL BASICSLooping
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328APPENDIX ■ PERL BASICSuse stri
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330APPENDIX ■ PERL BASICSuntil ($
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332APPENDIX ■ PERL BASICSuse stri
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334APPENDIX ■ PERL BASICSdoneAll
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336APPENDIX ■ PERL BASICS$ perl r
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338APPENDIX ■ PERL BASICSSummaryT
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340■INDEXmethods for retrieving r
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342■INDEXdo() method for, 62dumpi
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344■INDEXhello option for Net::SM
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346■INDEXNet::DNS module, 125-128
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348■INDEXrecord with Net::DNS mod
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350■INDEXstoring mail server in e
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352■INDEXlogging based on, 229pri
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