load-on-startup problem tomcat

1
votes

I want to load a class on tomcat startup which will actually initialize variables in other classes.

i have edited the appName/WEB-INF/web.xml as follows

<servlet>
    <servlet-name>LoadConfigurations</servlet-name>
    <servlet-class>Loader.LoadConfigurations</servlet-class>
    <init-param>
      <param-name>env</param-name>
      <param-value>dev</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

and i have placed my servlet LoadConfiguration in /appName/WEB-INF/classes

how do i check whether the servlet is beig called or not ? because when i try to display the value from initialized class it returns null

4
javatomcat
try keeping logs or System.out.println("Inside Constuctor") inside constructor and init() method start and end. check if you are getting the logs. - Jayesh

4 Answers

1
votes

There are two problems:

  1. The compiled class needs to go into a folder structure base on the package name. In your case a folder called Loader

  2. In order to call the servlet, you need to add a <ServletMapping> to your web.xml file

1
votes

The container should call your servlets init() method when the servlet is initialized. Implement/override that method and try writing something to the log from there.

1
votes

This is how I fix it on tomcat 9:

  1. Edit the conf/context.xml file and add reloadable="false" to the <Context> tag.

    <Context reloadable="false">

  2. Edit the conf/server.xml file and add deployOnStartup="false" to the <Host> tag.

    <Host appBase="webapps" deployOnStartup="false" …>

0
votes

This is the solution for Tomcat 7.0

Step 1: Create war file for your webapp/servlets. If you are using Eclipse, File->Export->Web->WAR file, and save it to a known location.

Step 2: Find out the home folder for your tomcat. For that, go to tomcat/apache-tomcat-7.0.41/bin and execute ./startup.sh This will print out couple of global variable names. Note down the one for CATALINA_HOME.

Step 3: Copy the war file from Step 1 in CATALINA_HOME/webapps

Step 4: Next, Create an xml file in CATALINA_HOME/conf/{Engine}/localhost/MyServlets.xml : 

<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
<Context deployOnStartup="true" docBase="/home/ubuntu/Downloads/apache-tomcat-7.0.42/webapps/" reloadable="true">
<Manager pathname=""/>
</Context>

Change docBase to point to location where you copied the war file in Step 3.

Now, you can go go to tomcat/apache-tomcat-7.0.41/bin and execute ./startup.sh. Your servlets will be automatically started. Hope this helps.