when you are using tomcat as you application server for not small application you can easy get (out of memory exception). this is because the default heap size tomcat use is small and suitable only for small web applications.

to set the start and maximum heap size run the following command before starting your tomcat:

export CATALINA_OPTS=”-Xms256m -Xmx512m”


export JAVA_OPTS=”-Xms256m -Xmx512m”

this will create environment variable called CATALINA_OPTSĀ  or JAVA_OPTS contains the required options to make tomcat start heap size 256M and maximum heap size 512M.


In this post I’ll talk about how to use connection pooling in struts running on tomcat server:

you will need to edit in the following places:

  • META-INF/context.xml
  • WEB-INF/web.xml

first you need to add a context.xml file to your application to be used by tomcat application server when defining and creating your application context.

To do that create a folder called META-INF beside your WEB-INF.

in this folder create file and name it context.xml

open this file and add the following code:

<Context path=”/yourAppPath” docBase=”yourAppDocBase
debug=”5″ reloadable=”true” crossContext=”true”>
<Resource name=”jdbc/resourceName” auth=”Container” type=”javax.sql.DataSource”
maxActive=”100″ maxIdle=”10″ maxWait=”10″
username=”userName” password=”Password” driverClassName=”com.mysql.jdbc.Driver”

replace names in Bold with your application parameters resourceName is the name of the datasource that you will use. the previous code creates a new database resource on your application context.

now you need to create a reference to the created resource. edit your web.xml and add the following code:

<description>DB Connection</description>

replace names in Bold with your application parameters.

now you only need to know how to get the datasource from your code:

Context ctx = new InitialContext();

DataSource ds = (DataSource) ctx.lookup(“java:comp/env/jdbc/resourceName“);

Connection connection = ds.getConnection();

and you can enjoy using the new connection

I wish that I made this topic clear and I’ll be happy to receive your comments and questions.