さくっとくんでみた。

設定ファイル等

IndexAction

package action;

import java.util.Map;

import org.apache.struts2.convention.annotation.Action;
import org.apache.struts2.convention.annotation.Namespace;
import org.apache.struts2.convention.annotation.ParentPackage;
import org.apache.struts2.convention.annotation.Result;
import org.apache.struts2.convention.annotation.Results;
import org.apache.struts2.interceptor.SessionAware;

import com.opensymphony.xwork2.ActionSupport;

@Namespace("/")
@ParentPackage("tiles-default")
@Action("index")
@Results({
		@Result(name = "success", location = "index_jsp", type = "tiles"),
		@Result(name = "input", location = "index_jsp", type = "tiles"),
		@Result(name = "error", location = "index_jsp", type = "tiles")
})
public class IndexAction extends ActionSupport implements SessionAware, SessionKey {

	protected Map<String, Object> session;

	@Override
	public String execute() throws Exception {

		return SUCCESS;
	}

	public void setSession(Map<String, Object> session) {
		this.session = session;
	}

}

index.jsp

<%@ taglib prefix="tiles" uri="http://tiles.apache.org/tags-tiles"%>
<%@ taglib prefix="tilesx" uri="http://tiles.apache.org/tags-tiles-extras"%>
<%@ taglib prefix="s" uri="/struts-tags"%>

<html>
	<head>
		<s:head />
		<title>
			<tiles:insertAttribute name="TITLE" />
		</title>
	</head>
	<body>
		<h2>
			<tiles:insertAttribute name="TITLE"/>
		</h2>
	</body>
</html>