May 13th, Lucek Consulting Basic Java Servlet/JSP Web Development David Lucek Lucek Consulting

May 13th, 2003 Download the Sample Application Download from select the downloads tabwww.lucek.com Includes the full source Unzip to c:\ drive or $HOME/lucek

May 13th, 2003 What is a Servlet? Java Servlets/JSP are part of the Suns J2EE Enterprise Architecture – The web development part Java Servlet – is a simple, consistent mechanism for extending the functionality of a web server – Are precompiled Java programs that are executed on the server side. – Require a Servlet container to run in Latest Servlet Spec is 2.3

May 13th, 2003 What is a Java Server Page (JSP) Java Server Pages (JSP) – A simplified, fast way to create dynamic web content – HTML or XML pages with embedded Java Code or Java Beans – Can be a mix of template data in HTML/XML with some dynamic content – A JSP is a complied to a Java Servlet automatically by the Servlet container, it is then cached Latest JSP Spec is 1.2

May 13th, 2003 Why Use Servlets? Work well in a Heterogeneous Environments – OS and platform neutral – Work with all major web servers (IIS, Apache,etc..) Well defined Web Architecture framework – Standard built in services such as: Standard Approach to Authentication using declarative security vice programmatic security Database connection pooling Complete support for sessions via cookies and/or URL re-writing – Has automatic fallback to URL re-writing

May 13th, 2003 Why Use Servlets Cont? – Robust Object-Orientated API in Java language Ever try to maintain a large ASP, Perl, or PHP site Clean separation of Controller/Logic from Presentation Efficient, scales very well There are good free Servlet/JSP containers and connectors – That run under both UNIX and win32

May 13th, 2003 J2EE Web Application Components Java Servlets – Extend off of HttpServlet JSP pages, normally for Presentation Java Beans – Normally used as value objects, pass to data to JSPs Tag Libraries – XML based JSP elements Web Deployment Descriptor – /web-inf/web.xml

May 13th, 2003 Web Deployment Descriptor /web-inf/web.xml – Part of the standard – Defines servlets used in the web application – Maps servlets to URLs – A servlet can map to many URLs Defines resources available to the web app Defines security constraints Defines other stuff like – Welcome file list – Session timeout – Error page mapping

May 13th, 2003 J2EE Web Directory Structure 1 Top Directory is normally the context Path – /tomcat/webapps/servletdemo – Normally, the URL would be – Contains JSP and other static content plus the web-inf directory /web-inf directory – This is a protected directory, can not point browser to any file in this directory – /classes – unpacked web application classes, auto-magically added to CLASS_PATH – /lib – web application JAR files – /taglib – tag library descriptor files

May 13th, 2003 J2EE Web Directory Structure 2 /web-inf/web.xml /web-inf/* – Would normally put any static or JSP files here – Protects them from Direct Invocation – Always best to call a JSP through a servlet first

May 13th, 2003 JSP Constructs 1 Used in JSP pages, pages that end *.jsp Comment Declaration Expression – Outputs to the Response stream – Like a printf to the browser – Do NOT use semi-colon to terminate the line Scriplets - contains Java Code –

May 13th, 2003 JSP Constructs 2 The value is: Value is empty Implicit objects always available in the JSP Page – request – Browsers Request Object Use to get HTTP headers, length etc.. – response - HttpResponse Object

May 13th, 2003 JSP Constructs 3 – session – internal HttpSession Object – pageContext – application – out, same as – config – servlet configuration – page – exception JSP Directives – Are messages or instructions to the JSP container

May 13th, 2003 JSP Constructs 4 – Do not produce any output – page directive Commonly used for importing class paths – include directive Good for including static content – taglib – lists the tag library descriptor location Required when using tab libraries

May 13th, 2003 Java Beans as Used in Web Apps Normally used for all data transfers and business components Similar to how Java Beans are used in Swing and AWT – But do not need the full implementation Must have no constructor or no-arg constructor Must have setter and getter methods for each property value JSP constructs/tags use Java Beans

May 13th, 2003 JSP Actions JSP actions are special tags that affect the output stream and are normally used with Java beans – Most commonly used:,, The code below will display the lastName property of the student bean on the output stream

May 13th, 2003 Servlet Container/Engine Servlets/JSP require a Container Apache Tomcat is the reference implementation of the Servlet/JSP Specs It is open source, small, install quickly,and is FREE Latest Version is Web Site: jakarta.apache.org/tomcat It include a simple HTTP 1.1 server, good enough for development and small intranets.

May 13th, 2003 Tomcat Install Requires a JDK, get and install into c:\jdk or $HOME/jdk Add JAVA_HOME to your environment and the bin directory to your PATH Good practice to unpack into c:\tomcat or $HOME/tomcat Add CATALINA_HOME to your environment and the bin directory to your PATH

May 13th, 2003 Tomcat Directory Structure Everything is relative to $CATALINA_HOME /bin – Startup/shutdown scripts /conf – Server.xml – main configuration file /common – common class and jar files used by Tomcat and web applications – Put JDBC drivers here /server – class and jar files used by Tomcat internally /shared – class and jar files for all web applications /webapps – This is where you put your web application in a sub-directory or external context file.

May 13th, 2003 Starting Tomcat /bin/startup.bat or startup.sh Point Browers to should see default pagehttp://localhost:8080 All the Docs are there on the default page! Check out the examples pages, good tutorials

May 13th, 2003 Other Development Tools 1 Ant Build Tool – Standard Java Build tool – Basic on UNIX make, but much better – Site: – Install in c:\ant or $HOME/ant Java IDE – Try NetBeans, it is nice – Tomcat is built in, but is an older version – Includes full Servlet and JSP debugging – Site:

May 13th, 2003 Other Development Tools 2 Junit – Standard Automated Unit Testing Tool – Site: Jedit – Slick Programmers Editor – Written in Java – Site: jedit.org

May 13th, 2003 Simple Servlet Application 1 See servletdemo code Mount the servletdemo, servletdemo/java/src, and servletdemo/web in NetBeans Explorer Tab For a Hello World Servlet look at: – Java/src/com/lucek/action/HelloWorld.java To build and run – $ cd servletdemo – Setup the proper build variables in the build.properties file – $ ant all – $ ant deploy – Point your browsers at

May 13th, 2003 Simple Servlet Application 2 Look at the web.xml file and how the same servlet can be mapped to many URLs Look at SimpleBean.java which should how to pass a Java Bean to a JSP page Look at the different ways a beans value can be obtained in the EditStudent.jsp

May 13th, 2003 Best Practices/Patterns Always Separate out the logic from the presentation – Use servlets for the logic/controller and JSPs for presentation – Ideally should never have Java Code in the JSP page Have a clean separation between your data access and controller layers (DAO) Always use DTO or value object Use a Model-View-Controller Architecture – Do not write it, use Struts – Site: jakarta.apache.org/struts/ Use Unit tests – Junit Automation via Ant build tasks

May 13th, 2003 What we have not talked about All the specific Servlet APIs Tag libraries Sessions, cookies JDBC service support from the container Container based authentication Lots of other stuff

May 13th, 2003 Next Presentation? Create a data driven web site using MySql and Servlets/JSP Setup Authentication Realm with declarative security Setup JDBC connection pooling Struts?