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 How to execute an initialization method before the first (web-)user interaction  

Answers

{{{ = #1 Using a Servlet Context Listener =

• Define the Servlet Context Listener in the web.xml.

  <listener>

  • <listener-class>

    • com.myCompany.MyServletContextListener

    </listener-class>

  </listener>

  Create your MyServletContextListener class implementing the javax.servlet.ServletContextListener interface and put your initialization code in the contextInitialized() method. }}}

{{{ = #2 Using a plug-in =

• Using a plug-in type class I believe should fit the bill here. This class is executed upon application start-up. These values that you call or intialize from whereever can be stored in application state for use by the rest of your application.

  Your plug-in class should extend org.apache.struts.action.PlugIn. Once you finish implementing the PlugIn interface, you would create an entry in your strut-config.xml to reference the PlugIn that you just created. You can find more information about it here:

  http://jakarta.apache.org/struts/userGuide/configuration.html#plugin_config

  You also might want to look at the JavaDocs for the PlugIn interface and read up on that as well. }}}

#3 Define statics

{{{ Define statics (maybe even private with access methods)

• in your extended servlet. }}}

public class yourActionServlet extends {{{ org.apache.struts.action.ActionServlet

• public void init() throws ServletException {

  • private static HashMap hashmap; //read XML file into variable hashMap

  } public static getHashMap(){ }}}
  • return hashmap;

    }  }

Then from your actions, simply:

yourActionServlet.getHashMap();

#4 Define another servlet entry in web.xml

{{{ <servlet>

• <servlet-name>

  • myInit

  </servlet-name> <servlet-class>

  • com.myCompany.MyServlet

  </servlet-class>

  <init-param>

  • <param-name>

    • config

    </param-name> <param-value>

    • db.driver=org.gjt.mm.mysql.Driver; db.username=root; db.password=rootWasHere$; db.maxconnect=10; db.minconnect=1; db.url=jdbc:mysql://localhost/idmt; log4j.rootCategory=ERROR,mylog;

      log4j.appender.mylog=org.apache.log4j.FileAppender; log4j.appender.mylog.File=System.err; log4j.appender.mylog.layout=org.apache.log4j.PatternLayout; log4j.appender.mylog.layout.ConversionPattern=%d{ddHHmmss MMM} %-5p %x - %m%n;

    </param-value>

  </init-param>

  <load-on-startup>

  • 1

  </load-on-startup>

• </servlet> }}}

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