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Configuring web servers and web applications

Configuring web servers and web applications. Server configuration vs. application configuration. A web server may run several web application Server configuration Affects all web application running on the server Port number Reference to username/password database Application configuration

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Configuring web servers and web applications

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  1. Configuring web servers and web applications Configuring web servers and web applications

  2. Server configuration vs. application configuration • A web server may run several web application • Server configuration • Affects all web application running on the server • Port number • Reference to username/password database • Application configuration • Affects only one web application • Welcome files • Mapping of Servlet names • Pages to handle errors • Setting session timeout • Securing the web application Configuring web servers and web applications

  3. Server configuration • No standard • Different web servers are configured in different ways • Tomcat • Configuration described in the file server.xml • TOMCAT_DIR/conf/server.xml • C:\Program Files\netbeans-5.5\enterprise3\apache-tomcat-5.5.17\conf\server.xml • Used if you run Tomcat outside NetBeans • C:\Documents and Settings\anders\.netbeans\5.5\apache-tomcat-5.5.17_base\conf\server.xml • Used if you run Tomcat inside NetBeans Configuring web servers and web applications

  4. Web application configuration • Standard • All Java enabled web servers should do it the same way • Configuration described in the file WEB-INF/web.xml • C:\andersb\wspj\login\web\WEB-INF\web.xml • C:\Program Files\netbeans-5.5\enterprise3\apache-tomcat-5.5.17\webapps\VerySimple\WEB-INF\web.xml Configuring web servers and web applications

  5. The structure of web.xml • The file web.xml is an XML file • Elements are tagged • The structure of the file is described in a DTD (Document Type Definition) file • It’s not free format! • Names on elements • Sub-elements • Sequence of elements • Web.xml can be edited • Using any text editor • Easy to make mistakes • Using NetBeans • NetBeans guides you Configuring web servers and web applications

  6. Editing web.xml with NetBeans Configuring web servers and web applications

  7. Assigning names to URLs • Servlets are Java classes • First letter in the Servlet name should be capital • Servlet class should be in a Java package • Problem • URL will look like …/package/ServletName • Package name is ugly • Capital letter • Solution • Assign the Servlet a virtual name in web.xml • <servlet>   <servlet-name>virtualname</servlet-name>   <servlet-class>package.ClassName</servlet-class> </servlet> • NetBeans does this when you create a new Servlet Configuring web servers and web applications

  8. Custom URLs • Sometimes you want to make a virtual URL for a Servlet (or JSP) • Usually shorter than the original URL • <servlet-mapping>   <servlet-name>virtualname</servlet-name>   <url-pattern>/someurl</url-pattern> </servlet-mapping> • NetBeans does this when you create a new Servlet Configuring web servers and web applications

  9. Remapping the /servlet URL pattern • Sometimes you don’t want users to call Servlets directly • Only through custom URLs • Make a special Servlet to say “sorry, no entrance” • Redirect all request for /servlet/* to this special Servlet • OH Listing 5.5 (page 290), web.xml, disabling the invoker servlet. Configuring web servers and web applications

  10. Initialization parameters • Servlets (and JSP) may need initialization parameters • Usually read and used in the init() method • The init() method is executed ONCE. • The doGet() method is executed at each request • Initialization parameters are (name, value) pair • Example • OH Listing 5.7 InitServlet.java • OH Listing 5.8 web.xml, initialization parameters Configuring web servers and web applications

  11. Welcome pages • If a URL does not refer to a file • http://laerer.rhs.dk/andersb/ • Which file to send in the response? • Web application holds a prioritized list of welcome files • Typically: index.html, index.jsp, etc. • <welcome-file-list> • <welcome-file>index.jsp</welcome-file> • <welcome-file>index.html</welcome-file> • </welcome-file-list> Configuring web servers and web applications

  12. Pages to handle errors • Two types of errors • HTTP status codes (not 2xx) • Called error codes in the Java terminology • Java exceptions • No caught by the Servlets • Errors can be caught and special pages send as response • Like a global try block • OH Listing 5.13 + 5.14, page 307 • OH Listing 5.17 + 5.18, page 310 Configuring web servers and web applications

  13. Session timeout • When a session has been inactive for some time it should be deleted • To save memory in the server machine • <session-config> • <session-timeout> • 30 • </session-timeout> • </session-config> • Time unit is minutes Configuring web servers and web applications

  14. Deployment • The file web.xml is called • “Web application deployment descriptor” • Deployment • Military: Inserting material and people into a battle • Application: Moving software into a new environment • Moving a web application into a new web server Configuring web servers and web applications

  15. Deploying a web application • When you build a web application you produce a WAR file • WAR: Web Application Archive • JAR: Java Application Archive • Zip file holding class files, web.xml, images, etc. But not conf/server.xml • WAR files can be moved to other servers • Put in the SERVER_HOME/webapps catalog Configuring web servers and web applications

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