How we can configure constants in Struts 2 ?

Constants provide a simple way to customize a Struts application by defining key settings that modify framework and plugin behavior.

Constant in struts.xml

<struts>

  <constant name="struts.devMode" value="true" />

  ...

</struts>

Constant in struts.properties

struts.devMode = true

Constant in web.xml

<filter>

    <filter-name>struts</filter-name>

    <filter-class>

       org.apache.struts2.dispatcher.FilterDispatcher

    </filter-class>

    <init-param>

        <param-name>struts.devMode</param-name>

        <param-value>true</param-value>

    </init-param>

</filter>