Serverside Scripting Martin Kruli by Martin Kruli v

Server-side Scripting Martin Kruliš by Martin Kruliš (v 1. 1) 3. 12. 2015 1

Web Server (Revision) � Serving Static Pages Apache configuration HTTP Request GET /myweb/index. html. . . /var/www/myweb/ ` Internet Client Web Server HTTP Response HTTP/1. 1 200 OK Content-Length: 1019 Content-Type: text/html; . . . <contents of index. html> index. html by Martin Kruliš (v 1. 1) 3. 12. 2015 2

Web Server (Revision) � Serving Dynamic Content HTTP Request /var/www/myweb/ GET /myweb/app. cgi. . . ` stdin Internet stdout Client Web Server app. cgi HTTP Response HTTP/1. 1 200 OK Content-Length: 2049 Content-Type: text/html; . . . <contents generated by cgi> by Martin Kruliš (v 1. 1) 3. 12. 2015 3

CGI � Common Gateway Interface ◦ One of the first standards for generating dynamic web content ◦ NSCA specification from 1993 how to invoke command line applications �Current version CGI 1. 1 (RFC 3875) from 2004 ◦ Specifies only the interface �Application may be written in any language �Important information and headers are set as environment variables, POST body is directed to std. input �Response is taken from the std. output Example 1 by Martin Kruliš (v 1. 1) 3. 12. 2015 4

Fast. CGI � CGI Issues ◦ Starting a process takes some system time ◦ Each process handles exactly one request �Unable to keep session/shared data in memory � Fast CGI Improvement ◦ Fast CGI server runs independently from web server �Keeps the process pool, resources, … ◦ Communicates with web server via socket/TCP ◦ Multi-request processing may be achieved by multiplexing or multiple connections (or both) by Martin Kruliš (v 1. 1) 3. 12. 2015 5

Web Server (Revision) � Integrating Scripting Modules HTTP Request /var/www/myweb/ GET /myweb/index. php. . . ` mod_php Internet Client Web Server index. php HTTP Response HTTP/1. 1 200 OK Content-Length: 1984 Content-Type: text/html; . . . <contents generated by php> by Martin Kruliš (v 1. 1) 3. 12. 2015 6

PHP � PHP: Hypertext Preprocessor ◦ Popular language originally designed for the web �The language has integrate API for handling requests �Things like URL parameters, POSTed data, headers, or server settings are presented in global variables ◦ PHP script code can be directly interleaved with HTML (or other type of generated content) �The script is embedded between <? php, ? > marks �The PHP interpret process the script and replace its body with its output in the document Example 2 by Martin Kruliš (v 1. 1) 3. 12. 2015 7

WSGI � Web Server Gateway Interface ◦ Universal interface between web servers and web applications designed for the Python language �Interface is called WSGI middleware and it is implemented by both sides (server and application) ◦ Specific new features �Routing requests to application objects (by URL) �Multiple applications may run in one process �Content post-processing (e. g. , by XSLT) �Load balancing (remote processing, forwarding, …) ◦ Similar APIs �Rack (Ruby), PSGI (Perl), JSGI (Java. Script) by Martin Kruliš (v 1. 1) Example 3 3. 12. 2015 8

ASP. NET � ASP. NET ◦ Microsoft solution built on. NET platform �Supports all. NET languages (C#, VB, …) ◦ Successor to Microsoft’s Active Server Pages ◦ Requires Microsoft IIS web server �Mono version (mod_mono and Fast. CGI) exists ◦ Web. Forms �Basic building blocks for ASP. NET web pages �Similar HTML interleaving syntax as PHP �The idea is to design web pages in the same manner as desktop applications by Martin Kruliš (v 1. 1) 3. 12. 2015 9

ASP. NET � ASP. NET ◦ Web. Forms �Event-based model, events may be processed at server �The forms automatically serializes the whole state ◦ Razor syntax �Block starts with @ and does not require explicit closing ◦ MVC �Alternative type of ASP. NET applications �Default view engine is either Razor (. cshtml, . vbhtml), or Web Forms (. aspx) �Controllers are. NET classes, methods are actions �Routers select controller class and invoke an action by Martin Kruliš (v 1. 1) 3. 12. 2015 10

JSP � Java Server Pages ◦ Java-based solution for dynamic web pages ◦ Requires web server with servlet container �Apache Tomcat, Jetty, … ◦ Supports both “simple” PHP-like approach and MVC �Uses <%, %> marks for scriptlet-HTML interleaving �MVC usually uses Java. Beans as the model and Java servlets as the controller ◦ Java compilation �Compiler is integrated in the web server and compiles the page when first needed (or when changed) by Martin Kruliš (v 1. 1) 3. 12. 2015 11

Ruby on Rails � Ruby on Rails ◦ Ruby scripting language + Rails web framework ◦ Basic philosophy �DRY (Don’t Repeat Yourself) – avoid code duplication �Convention Over Configuration – our way is the “best” ◦ Very strict style of application development �Improves efficiency, but ties your hands ◦ Specific structure of the application �Reflects the MVC pattern �$> rails new myapp �Generates new application structure in. /myapp by Martin Kruliš (v 1. 1) 3. 12. 2015 12

Ruby on Rails � Representational State Transfer (REST) ◦ Architectural abstraction for distributed systems ◦ The application is formed by resources �Resources are identified by URL http: //myapp. com/galery/2013/photo/42 ◦ Components of the application communicate over the network and exchange resource representations �Representation is typically HTML, XML, or JSON ◦ The API is built over HTTP and is hypertext driven �GET http: //myapp. com/galery/2013 �DELETE http: //myapp. com/galery/2013/photo/42 by Martin Kruliš (v 1. 1) 3. 12. 2015 13

Node. js � Java. Script Server-side Platform ◦ Basically a Google V 8 Java. Script engine compiled as CLI script interpreter �V 8 is used in Chrome and it is the fastest JS interpreter ◦ Contains many pre-built packages for server-side application development (sockets, HTTP, …) �HTTP server is embedded in the application, so the programmer may tune it for specific needs ◦ Aims for fast developed single-language solutions �Using Javascript on client and server allows some level of code sharing Example 4 by Martin Kruliš (v 1. 1) 3. 12. 2015 14

Statistics Web Programming Languages Usage (March 2013) PHP ASP. NET JSP Cold. Fusion Perl Ruby Python by Martin Kruliš (v 1. 1) 3. 12. 2015 15

Server-side Scripting � Client-server Architectures ◦ Strict separation of two application parts �Client - data presentation, user interface �Server – business logic, data storage ◦ Both sides are connected via specific API (HTTP) �The communication latency and overhead influence the application design ◦ Three-tier architecture �Server part is overloaded, so we separate the data storage and management into separate tier ◦ Thick client �Functionality is slowly shifting to the client-side by Martin Kruliš (v 1. 1) 3. 12. 2015 16

Server-side Scripting � Specific Issues of the Server Side ◦ Traditional web applications �Work in batches – client wants to perform a large task with each HTTP request �Download a page full of formatted data �Submit a form and generate a response �Difficult state management (HTTP is stateless) �Code replication and dependency injections ◦ Modern web applications �Just a remote API for AJAX calls �Difficult to integrate AJAX API into existing applications, or create applications that work both ways by Martin Kruliš (v 1. 1) 3. 12. 2015 17

Web Design Patterns � Model-View-Controller View Model Invoking actions Database Dataflow by Martin Kruliš (v 1. 1) 3. 12. 2015 18

Web Design Patterns � Model-View-Controller ◦ A guideline how to divide code and responsibility ◦ Basis for many frameworks ◦ Model �Uniform data API for the application �Communicates with DB/file storage/… �Simplifies portability to other storage types �Transparently handles encoding, integrity checks, transactions, data pre/post-processing, … by Martin Kruliš (v 1. 1) 3. 12. 2015 19

Web Design Patterns � Model-View-Controller ◦ View �User interface, data presentation �Typically responsible for generating HTML �Automatic sanitization of presented data (<, > chars) �Translations for multilingual applications �Templates �Mechanisms that separate HTML coding from application programming �Allow implementing View features (mentioned above) in declarative (instead of imperative) manner by Martin Kruliš (v 1. 1) 3. 12. 2015 20

Web Design Patterns � Model-View-Controller ◦ Controller �Integrates business (application) logic �Issues commands to view and model �Process user requests �Requests for displaying content (typically GET request) �Requests for modifying app. status (typically POST req. ) �Typically implements other design patterns �Front controller, command, … �Alternative – Model-View-Presenter �More advanced form of MVC �View is more separated and does not access model directly by Martin Kruliš (v 1. 1) 3. 12. 2015 21

Discussion by Martin Kruliš (v 1. 1) 3. 12. 2015 22