Servlets technology awareness

1
Servlets - technology awareness

• The object of this session is to introduce
  web-enabling servlet technology
• Servlets are based on Java technology
• Servlets are also based on HTTP (Web) technology

2
Servlets - technology awareness

• Like anything in Java it takes time to get used
  to
• Simple once you know Java understand the
  libraries
• Why are they not used by many firms for
  e-commerce?
• Maybe just inertia? Steep learning curve?

3
What is a Servlet?

• A servlet is a Java program that runs on a server
  and produces HTML pages dynamically
• A servlet produces HTML pages in response to
  client requests - these pages are sent to the
  clients web browser
• The trick is that a servlet may perform any
  operation that a Java application does e.g access
  a database
• You can send to the client HTML pages and forms
  with embedded data

4
Nuts and bolts

• A servlet is a Java class that implements the
  Servlet interface
• A servlet runs in the context of a process called
  a servlet engine
• Servlets can be invoked by a variety of clients -
  i.e. web browser, JavaServer Pages and .shtml or
  .ssi, server-side includes
• Just like applets, servlets use the Java Virtual
  Machine(JVM)

5
Benefits of Servlets

• Servlets web-enable your application - they are
  an alternative to CGI based applications
• Servlet class object can exist in a servlet
  engine in anticipation of a request - this is
  handy
• response quick to client requests
• can handle multiple clients simultaneously
• Servlets are secure - files are on the secure
  side of the firewall

6
Benefits of Servlets

• Used as an alternative to applets in a (very)
  thin client internet solution - this is the
  preferred industry solution
• can be used with a variety of database drivers
• e.g. JDBC, ODBC
• Can connect to standard databases

7
Life cycle of a Servlet

• Load (done by Servlet engine)
• Initialise
• Execute
• Destroy
• All work is done inside the server
• After initial setup client response is fast

8
Sources for servlets

• In true object-oriented fashion we can find
  pre-written servlets on the web
• e.g.
• http//www.ibazaar.com/jasp/servlets.shtm
• http//www.cetus-links.org/oo_java_servlets.html
• And free server software to test them
• http//java.about.com/cs/servlets/a/tomcat.htm