Struts 2 MVC maintaining login session

Hi I'm trying to maintain my login session in a Struts 2 proyect. Specificly I want prohibit someone from entering a url thats only accessible if you are previously loged in.

This is my struts.xml

    <?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN"
    "http://struts.apache.org/dtds/struts-2.1.dtd">

    <struts>
        <package name="default" extends="struts-default">
        <action name="LoginAction" class="com.mmedus.Action.OnlyAction"method="loginMethod">
            <result name="success">/home.jsp</result>
            <result name="error">/error.jsp</result>
        </action>
        <action name="RegisterAction" class="com.mmedus.Action.OnlyAction" method="registerMethod">
            <result name="success">/successUser.jsp</result>
            <result name="error">/error.jsp</result>
        </action>
        <action name="CreateMatchAction" class="com.mmedus.Action.OnlyAction" method="createMatchMethod">
            <result name="success">/successMatch.jsp</result>
            <result name="error">/error.jsp</result>
        </action>
        <action name="DisplayAllMatchAction" class="com.mmedus.Action.DisplayAllMatchAction"  method="execute">
            <result name="success">/displayAllMatch.jsp</result>
            <result name="error">/error.jsp</result>
        </action>
        <action name="DisplayMatch" class="com.mmedus.Action.DisplayMatchAction" method="execute">
            <result name="success">/displayMatch.jsp</result>
            <result name="error">/error.jsp</result>
        </action>
        <action name="AddPlayer" class="com.mmedus.Action.DisplayMatchAction" method="addPlayer">
            <result name="success">/home.jsp</result>
            <result name="error">/error.jsp</result>
        </action>
    </package>
</struts>

My OnlyAction class that validates my login

    package com.mmedus.Action;

    import com.opensymphony.xwork2.Action;
    import com.mmedus.Form.*;
    import com.mmedus.Model.*;

    public class OnlyAction{
    private Form form = new Form();
    private User user = new User();
    private Match match = new Match();
    private MatchForm matchForm= new MatchForm();

    public Form getForm() {
        return form;
    }

    public void setForm(Form form) {
        this.form = form;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public Match getMatch() {
        return match;
    }

    public void setMatch(Match match) {
        this.match = match;
    }

    public MatchForm getMatchForm() {
        return matchForm;
    }

    public void setMatchForm(MatchForm matchForm) {
        this.matchForm = matchForm;
    }

    public String loginMethod(){
        String status = Action.ERROR;       

        getUser().setUsername(getForm().getUsername());
        getUser().setPassword(getForm().getPassword());

        if(getForm().getService().getDao().getUser(getUser())){
            status = Action.SUCCESS;
        }else{
            status = Action.ERROR;
        }       
        return status;
    }

    public String registerMethod(){
        String status = "error";

        getUser().setUid(getForm().getUid());
        getUser().setUname(getForm().getUname());
        getUser().setUsername(getForm().getUsername());
        getUser().setPassword(getForm().getPassword());
        getUser().setAddress(getForm().getAddress());

        if(getForm().getService().getDao().addUser(getUser())){
            status = Action.SUCCESS;
        }else{
            status = Action.ERROR;
        }
        return status;
    }

    public String createMatchMethod(){
        String status = "error";

        getMatch().setName(getMatchForm().getName());
        getMatch().setNumPlayers(getMatchForm().getNumPlayers());
        getMatch().setLocation(getMatchForm().getLocation());

        if(getMatchForm().getService().getDao().addMatch(getMatch()) || getMatch().getName()=="" || getMatch().getNumPlayers()==0 || getMatch().getLocation()==""){
            status = Action.SUCCESS;
        }else{
                status = Action.ERROR;
        }
        return status;  
    }

    /*
    public String displayMatchMethod(){
        String status = "error";

        getMatch().setName(getMatchForm().getName());
        getMatch().setNumPlayers(getMatchForm().getNumPlayers());
        getMatch().setLocation(getMatchForm().getLocation());

        if(getMatchForm().getService().getDao().getMatch(getMatch())){
            status = Action.SUCCESS;
        }else{
            status = Action.ERROR;
        }       
        return status;

    }
    */

}

Can someone help me please? Let me know if there is more code needed. Thanks.