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Intro to Servlets

Intro to Servlets. Lec 26. Web-Based Enterprise Applications in Java. Figure shows a simplified view of one application and its layers. Java Servlets. JVM. Request. Client/ browser. Server. Servlet. Response. Extends the functionality of the server by

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Intro to Servlets

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  1. Intro to Servlets Lec 26

  2. Web-Based Enterprise Applications in Java Figure shows a simplified view of one application and its layers.

  3. Java Servlets JVM Request Client/ browser Server Servlet Response Extends the functionality of the server by Generating HTML pages dynamically

  4. What Do They Do? • Anything that java can do (e.g. connect to database services) • Handle data/requests sent by users (clients) • Create and format results • Send results back to user

  5. Java Servlets • Advantages over other SSP technologies: • Can use the Java APIs e.g. JDBC. • Persistent between invocations, avoiding process instantiations. • Portable across operating systems and servers. • Good security. • Is integrated closely with the J2EE environment.

  6. Software Requirements

  7. Software Requirements • To use Java servlets, following softwares will be needed • J2SE • Additional J2EE based libraries for servlets such as servlet-api.jar, jsp-api.jar. You can download these APIs separately but they are also available with the web server you’ll be using. • A capable servlet web engine (web server)

  8. Jakarta Servlet Engine (Tomcat) • Jakarta is an Apache project • Tomcat is one of its subprojects • Tomcat is the official reference implementation for the Java servlet and JavaServer pages technologies (according to Sun’s specifications) • Tomcat is developed in an open and participatory environment and released under the Apache software license

  9. Environment Setup

  10. Environment Setup Steps • Download the Apache Tomcat Server • Install Tomcat • Set the JAVA_HOME variable • Set the CATALINA_HOME variable • Set the CLASSPATH variable • Test the Server

  11. Download the Apache Tomcat Server • From the http://jakarta.apache.org • Download the zip file for the current release of Jakarta Tomcat • For windows, there is also a .exe installer

  12. Install Tomcat • Installing .zip file • Unzip the file into a location (e.g. C:\) • The zip file had embedded subdirectories(e.g.,jakarta-tomcat-5.5.9). • C:\ jakarta-tomcat-5.5.9generally referred as install_dir • Installing .exe file • Check the handouts

  13. Set the JAVA_HOME variable • Set the JAVA_HOME environment variable to tell Tomcat where to find Java • This variable should list the base JDK installation directory, not the bin subdirectory JAVA_HOME = c:\j2sdk1.5.0

  14. Set the CATALINA_HOME variable • Set the CATALINA_HOME environment variable to refer to the top-level directory of the Apache Tomcat installation, not the bin subdirectory CATALINA_HOME = c:\jakarta-tomcat-5.5.9

  15. Set the CLASSPATH variable • Since servlets and JSP are not part of the J2SE, javac doesn’t know about the servlet and jsp classes • The standard Tomcat locations for these files are • install_dir/common/lib/servlet-api.jar • install_dir/common/lib/jsp-api.jar • You need to include both files in your CLASSPATH

  16. Test the Server • Before making your own Servlets and JSP, verify that the server can start • Runinstall_dir/bin/startup.bat • Enter the URL http://localhost:8080 in your browser and make sure you will get the Tomcat homepage

  17. Lets do it LIVE

  18. Tomcat Directory Structure my-app

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