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Internetteknologi (ITNET2)

Internetteknologi (ITNET2). Præsentation 21: Common Gateway Interface (CGI) illustreret med Perl og C. Mission. Efter denne 2x35 lektion vil I:

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Internetteknologi (ITNET2)

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  1. Internetteknologi (ITNET2) Præsentation 21: Common Gateway Interface (CGI) illustreret med Perl og C

  2. Mission • Efter denne 2x35 lektion vil I: • Have opnået et basalt kendskab til Common Gateway Inteface (CGI) teknologien, med udgangspunkt i Perl, og forstå dens ligheder og forskelle med andre server side teknologier, såsom JSP/Servlets og ASP.NET • Dette er ikke et Perl kursus – så I vil ikke have lært Perl • Have set hvordan alternativt C kan anvendes m.f.

  3. Indhold i denne præsentation • Kort introduktion til CGI • Hvordan virker det? • Eksempler på CGI og Perl • Om fremtiden for CGI og Perl • CGI og C

  4. Hvad er “CGI”? • Common Gateway Interface • Standard til at afvikle et eksekverbart program (eller et script i Perls tilfælde) via Web servere • Web serveren skal blot vide hvem der har ansvaret for at afvikle koden, hvorefter den redelegere requestet • (Næsten) alle sprog kan bruges til at lave CGI programmer med (standard in/out + environment) • Herunder C/C++ , og de mest anvendte Perl og Python • CGI/Perl/C var i mange år det foretrukne værktøj til dynamisk server-side programmering, indtil ASP/ASP.NET, JSP/Servlets, PHP kom frem

  5. CGI Historie • Opfundet af NCSA Software Development Group • 1993? Svært at finde en præcis reference • Samme som opfandt Mosaic browseren (forløberen til Netscape) • Og NCSA httpd (én af de første web servere) • Find specificationen på: • http://hoohoo.ncsa.uiuc.edu/cgi/interface.html • Er i dag reelt en defacto standard for program kald

  6. Server side scripting - CGI Bruger indtaster data i form feltet i browser og taster submit: http://feedbackForm.htm Webserver findes via IP adresse & DNS Lytter på port f.eks. 80 1 HTTP Request (over TCP/IP) GET /feedback.pl 2 Webserveren modtager requestet: Finder det rette program via CGI interfacet, feks. (feedback.pl) En ny proces spawnes og programmet afvikles med de givne parametre, og resultatet afleveres på output stream LIGHEDER MED ASP/JSP? En typisk Header kunne se ud som følger: HTTP/1.0 200 OK Server: Netscape-Communications/1.1 Date: Tuesday, 25-Nov-97 01:22:04 GMT Last-modified: Thursday, 20-Nov-97 10:44:53 GMT Content-length: 6372 Content-type: text/html <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <HTML> ... her følger resten af dokumentet 3 Browseren modtager response: Renderer HTML dokumentet til brugervenlig form

  7. Eksempler • I har prøvet at bruge både Servlets/JSP, PHP og ASP.NET – nu skal vi se hvordan CGI fungerer i relation til først et C eksempel og herefter et Perl eksempel • Her følger et par slides der kort illustrere dette

  8. Vi ser at HTML er indlejret. import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorld extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<body>"); out.println("<head>"); out.println("<title>Hello World!</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>Hello World!</h1>"); out.println("</body>"); out.println("</html>"); } } Server side:Servlet eksempel Resultatet <html> <head> <title>Hello World!</title> </head> <body bgcolor="white"> <a href="/examples/servlets/helloworld.html"> <img src="/examples/images/code.gif" height=24 width=24 align=right border=0 alt="view code"></a> <a href="/examples/servlets/index.html"> <img src="/examples/images/return.gif" height=24 width=24 align=right border=0 alt="return"></a> <h1>Hello World!</h1> </body> </html>

  9. Alt vi skal bruge er standard IO #include <stdio.h> main(int argc, char *argv[]) { char *cl; printf("Content-type: text/html%c%c",10,10); if(strcmp(getenv("REQUEST_METHOD"),"GET")) { printf("This script should be referenced with a METHOD of POST.\n"); exit(1); } else { printf("<p>You have contacted me using the POST method</p>"); } cl = getenv("QUERY_STRING"); printf("<p>"); printf("The Content of Query_String was: "); printf(cl); printf("</p>"); return 0; } Server sideCGI/C Page Vi anvender getenv til at kommunikere med serveren (environment variable) HTTP Get parametre strengen Kommer i env-var QUERY_STRING

  10. 1 #!/usr/bin/perl 2 # Fig. 27.11: fig27_11.pl 3 # Program to display CGI environment variables. 4 5 use CGI qw( :standard ); 6 7 $dtd = 8 "-//W3C//DTD XHTML 1.0 Transitional//EN\" 9 \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"; 10 11 print( header() ); 12 13 print( start_html( { dtd => $dtd, 14 title => "Environment Variables..." } ) ); 15 16 print( "<table style = \"border: 0; padding: 2; 17 font-weight: bold\">" ); 18 19 print( Tr( th( "Variable Name" ), 20 th( "Value" ) ) ); 21 22 print( Tr( td( hr() ), td( hr() ) ) ); 23 24 foreach $variable ( sort( keys( %ENV ) ) ) { 25 26 print( Tr( td( { style => "background-color: #11bbff" }, 27 $variable ), 28 td( { style => "font-size: 12pt" }, 29 $ENV{ $variable } ) ) ); 30 31 print( Tr( td( hr() ), td( hr() ) ) ); 32 } 33 34 print( "</table>" ); 35 print( end_html() ); Server sideCGI/Perl Page CGI bibliotektet wrapper kommunikation med web serveren Metoderne kommer fra CGI bibliotektet

  11. Hvad skal der til for at køre CGI • JSP og Servlets bruger en ”Servlet Container” m. egen VM • Apache Tomcat, BEA Weblogic, Oracle AS, IBM WebSphere – alle standardiseret • ASP & ASP:NET bruger Windows og IIS Web server / .NET CLR • CGI/Perl er understøttet af stort set alle Web servere og operativsystemer, men der skal evt. downloades en operativsystem specifik perl fortolker. • Brug f.eks. Apache Web serveren, med mod_cgi/mod_perl modulet tilføjet • CGI/C – CGI/C++ såfremt det kan kompileres på platformen kan det som regel også afvikles af Web serveren hvis den understøtter CGI (som f.eks. Apache)

  12. PERL • PERL: Practical Extraction and Report Language • Høj-niveau programmeringssprog • Fortolket programmeringssprog (perl.exe) • Løst typet • Bruges som konsol sprog af administratorer til overvågning og rapporteringsopgaver • Virkeligt stærkt til streng behandling • Vandt derfor tidligt indpas på WWW i forb. Med CGI • (www.perl.com)

  13. PERL History • Opfundet af Larry Wall i 1987 • Perl 2: 1988 • Perl 3: 1989 • Perl 4: 1992 • Standard in UNIX – small programs only • Perl 5: 1994 • Full programming language – total rewrite • Subversions of Perl 5 • Rasmus Lehrdorf uses Perl to create PHP: 1995 • PerlNET: .NET Wrapper for Perl (runs unmanged) • Perl 6: currently under development (open source) • New: VM instead of interpreter

  14. The %ENV hash is a built-in table in Perl that contains the names and values of all the environment variables. 1 #!/usr/bin/perl 2 # Fig. 27.11: fig27_11.pl 3 # Program to display CGI environment variables. 4 5 use CGI qw( :standard ); 6 7 $dtd = 8 "-//W3C//DTD XHTML 1.0 Transitional//EN\" 9 \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"; 10 11 print( header() ); 12 13 print( start_html( { dtd => $dtd, 14 title => "Environment Variables..." } ) ); 15 16 print( "<table style = \"border: 0; padding: 2; 17 font-weight: bold\">" ); 18 19 print( Tr( th( "Variable Name" ), 20 th( "Value" ) ) ); 21 22 print( Tr( td( hr() ), td( hr() ) ) ); 23 24 foreach $variable ( sort( keys( %ENV ) ) ) { 25 26 print( Tr( td( { style => "background-color: #11bbff" }, 27 $variable ), 28 td( { style => "font-size: 12pt" }, 29 $ENV{ $variable } ) ) ); 30 31 print( Tr( td( hr() ), td( hr() ) ) ); 32 } 33 34 print( "</table>" ); 35 print( end_html() ); The import tag :standard imports a predefined set of standard functions. Fig27_11.pl Instruct the Perl script to print a valid HTTP header, using function header from the CGI library. The use statement instructs Perl programs to include the contents (e.g., functions) of predefined packages called modules. The start_html function prints the document type definition for this document, as well as several opening XHTML tags (<html>, <head>, <title>, etc., up to the opening <body> tag). Function keys returns an unordered array containing all the keys in the %ENV hash. Specifies the value for the attribute style.

  15. Program Output

  16. Eksempel på brug af parametre • Vi husker fra JSP/Servlets og ASP, at alt kommunikation primært foregik via FORM elementer • Dette er også tilfældet i CGI/Perl • I det følgende gives et eksempel på dette • Først en simpel registreringsform • Og herefter en CGI/Perl side der henter data fra HTTP requestet

  17. 1 <!DOCTYPE html PUBLIC"-//W3C//DTD XHTML 1.0 Transitional//EN" 2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3 4 <!-- Fig. 27.12: fig27_12.html --> 5 6 <html> 7 <head> 8 <title>Sample form to take user input in XHTML</title> 9 </head> 10 11 <body style ="font-face: arial; font-size: 12pt"> 12 13 <div style ="font-size: 14pt; font-weight: bold"> 14 This is a sample registration form. 15 </div> 16 17 <br /> 18 Please fill in all fields and click Register. 19 20 <form method ="post"action ="/cgi-bin/fig27_13.pl"> 21 22 <img src ="images/user.gif"/><br /> 23 24 <div style ="color: blue" > 25 Please fill out the fields below.<br /> 26 </div> 27 28 <img src ="images/fname.gif"/> 29 <input type ="text"name ="fname"/><br /> 30 <img src ="images/lname.gif"/> 31 <input type ="text" name = "lname"/><br /> 32 <img src = "images/email.gif"/> 33 <input type ="text"name = "email"/><br /> 34 <img src = "images/phone.gif"/> 35 <input type ="text"name = "phone"/><br /> Fig27_12.html Form element which indicates that, when the user clicks Register, the form information is posted to the server. The statement action="cgi-bin/ fig27_13.pl" directs the server to execute the fig27_13.pl Perl script (located in the cgi-bin directory) to process the posted form data. Exactly like JSP/PHP/ASP.NET

  18. 36 37 <div style ="font-size: 10pt"> 38 Must be in the form (555)555-5555.<br /><br /> 39 </div> 40 41 <img src = "images/downloads.gif"/><br /> 42 <div style = "color: blue"> 43 Which book would you like information about?<br /> 44 </div> 45 46 <select name ="book"> 47 <option>Internet and WWW How to Program 2e</option> 48 <option>C++ How to Program 3e</option> 49 <option>Java How to Program 4e</option> 50 <option>XML How to Program 1e</option> 51 </select><br /><br /> 52 53 <img src = "images/os.gif"/><br /> 54 <div style ="color: blue"> 55 Which operating system are you currently using? 56 </div><br /> 57 58 <input type ="radio"name ="os" 59 value ="Windows NT" checked/> 60 Windows NT<input type ="radio" 61 name ="os"value ="Windows 2000" /> 62 Windows 2000<input type ="radio" 63 name ="os"value ="Windows 98/me" /> 64 Windows 98/me<br /><input type ="radio" 65 name ="os"value ="Linux" /> 66 Linux<input type ="radio"name ="os" 67 value ="Other" /> 68 Other<br /><input type ="submit" 69 value ="Register"/> 70 </form> Fig27_12.html

  19. 71 </body> 72 </html> Fig27_12.htmlProgram Output

  20. Function param is part of the Perl CGI module and retrieves values from a form field’s value. Same as ASP’s Request(”param”) & JSP’s request.getParameter(”param”) 1 #!/usr/bin/perl 2 # Fig. 27.13: fig27_13.pl 3 # Program to read information sent to the server 4 # from the form in the fig27_12.html document. 5 6 use CGI qw( :standard ); 7 8 $os = param( "os" ); 9 $firstName = param( "fname" ); 10 $lastName = param( "lname" ); 11 $email = param( "email" ); 12 $phone = param( "phone" ); 13 $book = param( "book" ); 14 15 $dtd = 16 "-//W3C//DTD XHTML 1.0 Transitional//EN\" 17 \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"; 18 19 print( header() ); 20 21 print( start_html( { dtd => $dtd, 22 title => "Form Results" } ) ); 23 24 if ( $phone =~ / ^ \( \d{3} \) \d{3} - \d{4} $ /x ) { 25 print( "Hi " ); 26 print( span( { style => "color: blue; font-weight: bold" }, 27 $firstName ) ); 28 print( "!" ); 29 30 print( "\nThank you for completing the survey." ); 31 print( br(), "You have been added to the " ); 32 33 print( span( { style => "color: blue; font-weight: bold" }, 34 $book ) ); 35 print( " mailing list.", br(), br() ); Fig27_13.pl The if condition uses a regular expression to validate the phone number. The expression “\(” matches the opening parenthesis of the phone number. This sequence must be followed by three digits (\d{3}), a closing parenthesis, three digits, a hyphen and finally, four more digits. Dette kan også gøres i både JSP og ASP, men også i JavaScript – Client side

  21. Methods span and div add <span> and <div> tags to the page, respectively. If the phone number is not valid an error message is printed to the client 36 37 print( span( { style => "font-weight: bold" }, 38 "The following information has 39 been saved in our database: " ), br() ); 40 41 print( table( 42 Tr( th( { style => "background-color: #ee82ee" }, 43 "Name" ), 44 th( { style => "background-color: #9370db" }, 45 "E-mail" ), 46 th( { style => "background-color: #4169e1" }, 47 "Phone" ), 48 th( { style => "background-color: #40e0d0" }, 49 "OS" ) ), 50 51 Tr( { style => "background-color: #c0c0c0" }, 52 td( "$firstName $lastName" ), 53 td( $email ), 54 td( $phone ), 55 td( $os ) ) ) ); 56 57 print( br() ); 58 59 print( div( { style => "font-size: x-small" }, 60 "This is only a sample form. You have not been 61 added to a mailing list." ) ); 62 } 63 else { 64 print( div( { style => "color: red; font-size: x-large" }, 65 "INVALID PHONE NUMBER" ), br() ); 66 67 print( "A valid phone number must be in the form " ); 68 print( span( { style => "font-weight: bold" }, 69 "(555)555-5555." ) ); 70 Fig27_13.pl

  22. 71 print( div( { style => "color: blue" }, 72 "Click the Back button, and enter a 73 valid phone number and resubmit." ) ); 74 print( br(), br() ); 75 print( "Thank you." ); 76 } 77 78 print( end_html() ); Fig27_13.plProgram Output

  23. Standard Libraries available Wraps the reading of env and stdin Special HTML functions Sessions etc Using Extra Libraries for C Simplified query-results.cgi using cgihtml. #include "cgi-lib.h"#include "html-lib.h"int main(){   llist entries   read_cgi_input(&entries);   html_header();   html_begin("Query Results");   print_entries(entries);   html_end();   list_clear(&entries);}

  24. Eksempel på brug af Server-Side Includes (SSI eller .shtml) • Det er også muligt at opnå JSP/ASP lignende funktionalitet, dvs. med indlejrede ”tags” • Fra SHTML kan kommandoen ”EXEC” kaldes, der kalder et andet CGI script, og inkluder dets output – svarende til Server.Execute(”side.asp”) i ASP, og <jsp:include page=”side.jsp”/> i JSP. • I det følgende gives et eksempel på dette

  25. The command EXEC can be used to run CGI scripts and embed their output directly into a Web page. The ECHO command displays variable information. The ECHO command is followed by the keyword VAR and the name of the variable. For example, variable DATE_GMT contains the current date and time in Greenwich Mean Time (GMT). 1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3 4 <!-- Fig. 27.14: fig27_14.shtml --> 5 6 <html> 7 <head> 8 <title>Using Server Side Includes</title> 9 </head> 10 11 <body> 12 <h3 style ="text-align: center"> 13 Using Server Side Includes 14 </h3> 15 16 <!--#EXEC CGI="/cgi-bin/fig27_15.pl" --><br /> 17 18 The Greenwich Mean Time is 19 <span style ="color: blue"> 20 <!--#ECHO VAR="DATE_GMT" -->. 21 </span><br /> 22 23 The name of this document is 24 <span style ="color: blue"> 25 <!--#ECHO VAR="DOCUMENT_NAME" -->. 26 </span><br /> 27 28 The local date is 29 <span style ="color: blue"> 30 <!--#ECHO VAR="DATE_LOCAL" -->. 31 </span><br /> 32 Fig27_14.shtml

  26. 33 This document was last modified on 34 <span style ="color: blue"> 35 <!--#ECHO VAR="LAST_MODIFIED" -->. 36 </span><br /> 37 38 Your current IP Address is 39 <span style ="color: blue"> 40 <!--#ECHO VAR="REMOTE_ADDR" -->. 41 </span><br /> 42 43 My server name is 44 <span style ="color: blue"> 45 <!--#ECHO VAR="SERVER_NAME" -->. 46 </span><br /> 47 48 And I am using the 49 <span style ="color: blue"> 50 <!--#ECHO VAR="SERVER_SOFTWARE" --> 51 Web Server. 52 </span><br /> 53 54 You are using 55 <span style ="color: blue"> 56 <!--#ECHO VAR="HTTP_USER_AGENT" -->. 57 </span><br /> 58 59 This server is using 60 <span style ="color: blue"> 61 <!--#ECHO VAR="GATEWAY_INTERFACE" -->. 62 </span><br /> 63 64 <br /><br /> 65 <div style ="text-align: center; 66 font-size: xx-small"> 67 <hr /> Fig27_14.shtml

  27. 68 This document was last modified on 69 <!--#ECHO VAR="LAST_MODIFIED" -->. 70 </div> 71 </body> 72 </html> Fig27_14.shtmlProgram Output

  28. The file counter.dat, which contains the number of hits to date for the fig27_14.shtml Web page, is opened for input. Function open is called to create a filehandle to refer to the file during the execution of the script. 1 #!/usr/bin/perl 2 # Fig. 27.15: fig27_15.pl 3 # Program to track the number of times 4 # a Web page has been accessed. 5 6 use CGI qw( :standard ); 7 8 open( COUNTREAD, "counter.dat" ); 9 $data = <COUNTREAD>; 10 $data++; 11 close( COUNTREAD ); 12 13 open( COUNTWRITE, ">counter.dat" ); 14 print( COUNTWRITE $data ); 15 close( COUNTWRITE ); 16 17 print( header(), "<div style = \"text-align: center; 18 font-weight: bold\">" ); 19 print( "You are visitor number", br() ); 20 21 for ( $count = 0; $count < length( $data ); $count++ ) { 22 $number = substr( $data, $count, 1 ); 23 print( img( { src => "images/$number.gif" } ), "\n" ); 24 } 25 26 print( "</div>" ); Fig27_15.pl

  29. OO understøttelse i Perl: POOP Minder lidt om PHP 4 modellen http://www.codeproject.com/perl/camel_poop.asp POOP: OO Perl

  30. Også mulighed for DB adgang i PERL: DBI F.eks. MySQL drivere tilgængelige Se Deitel & Deitel eller www.perl.com Perl og Databaser

  31. CGI vs øvrige server-side sprog • Performance • CGI programmer spawnes og afsluttes for hver client request • performer dårligt ved mange samtidige request • Udover ny proces skal der også spawnes perl.exe (ved perl) • JSP/Servlets, ASP.NET og PHP håndterer flere samtidige requests mere intelligent • performer bedre ved mange samtidige request • Struktueringsmekanismer • Afhængigt af underliggende sprog • Ringe kontakt mellem CGI scripts og Web server • Mangler grundliggende objekter (f.eks. Session objektet) hvilket dog kan findes via eksterne libs

  32. Performance Comparison of Alternative Solutions For Web-To-Database Applications, by AMANDA W. WU, HAIBO WANG AND DAWN WILKINS, October 2000 http://rain.vislab.olemiss.edu/~ww1/Slide_Show_Images/SCC_Amanda/SCC_Amanda.pdf

  33. Om fremtiden for CGI I • Generelt kan man lave de fleste ting du kan lave i JSP/Servlets og/eller ASP/ASP.NET- i CGI/Perl, (eller CGI med et andet sprog) • Databaser, filadgang, regulære udtryk, algebra, logik … • Samtidigt findes der ufatteligt mange eksisterende scripts der kan køres, og mange sites bruger stadigvæk CGI til f.eks. Counter, FormMails, gæstebøger osv.

  34. Om fremtiden for CGI II • MEN: • CGI ikke velegnet til at udvikle større systemer • CGI har ikke IDE og debugging faciliteter • Svært at strukturere • Stærkt begrænset popularitet • DOG: • Vigtigt at kende teknologien – både historisk set – men også fordi der stadigvæk kører masser af CGI programmer hos kunder • Anvendeligt til indlejrede enheder • Godt til afvikling af ekstremt krævende databehandlingsalgoritmer

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