Struts wildcards can helps to reduce the repetition in your struts-config.xml file, as long as your Struts project is following some regular file structure. For example, in User module, to implement the CRUD function, your struts-config.xml may look like following

1. No Wildcards

You need to create four action mappings for each list, add, delete and update function, and a lot of repetition.

struts-config.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts-config PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 1.3//EN"

"http://jakarta.apache.org/struts/dtds/struts-config_1_3.dtd">

<struts-config>

	<action-mappings>

	 	<action

			path="/ListUserAction"

			type="com.mkyong.common.action.UserAction"

			parameter="ListUser"

			>

			<forward name="success" path="/pages/ListUser.jsp"/>

		</action>

		<action

			path="/AddUserAction"

			type="com.mkyong.common.action.UserAction"

			parameter="AddUser"

			>

			<forward name="success" path="/pages/AddUser.jsp"/>

		</action>

		<action

			path="/EditUserAction"

			type="com.mkyong.common.action.UserAction"

			parameter="EditUser"

			>

			<forward name="success" path="/pages/EditUser.jsp"/>

		</action>

		<action

			path="/DeleteUserAction"

			type="com.mkyong.common.action.UserAction"

			parameter="DeleteUser"

			>

			<forward name="success" path="/pages/DeleteUser.jsp"/>

		</action>

	</action-mappings>

</struts-config>

2. With Wildcards

With Struts wildcards feature, your struts-config.xml can cut down into one action mapping.

struts-config.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts-config PUBLIC

"-//Apache Software Foundation//DTD Struts Configuration 1.3//EN"

"http://jakarta.apache.org/struts/dtds/struts-config_1_3.dtd">

<struts-config>

	<action-mappings>

	 	<action

			path="/*UserAction"

			type="com.mkyong.common.action.UserAction"

			parameter="{1}User"

			>

			<forward name="success" path="/pages/{1}User.jsp"/>

		</action>

	</action-mappings>

</struts-config>

Let’s see an use case, try access via http://localhost:8080/StrutsExample/EditUserAction.do. The “EditUserAction.do” will match the “/*UserAction” pattern, and the * matched string “Edit” is represent by {1} for later use.

In above case, the wildcards action mapping will change from

       <action

		path="/*UserAction"

		type="com.mkyong.common.action.UserAction"

		parameter="{1}User"

	>

	<forward name="success" path="/pages/{1}User.jsp"/>

	</action>

to

       <action

		path="/EditUserAction"

		type="com.mkyong.common.action.UserAction"

		parameter="EditUser"

	>

	<forward name="success" path="/pages/EditUser.jsp"/>

	</action>

Conclusion

Both struts-config.xml samples have the same functionality, but with less repetition in wildcards support. However, DO NOT overuse this wildcards feature in your project, it’s less manageable than the normal declaration.