Cómo crear un formulario JSF con validación de datos AJAX

Estoy trabajando en un prototipo de formulario JSF para insertar datos en la tabla de base de datos utilizando la validación de datos AJAX. Esta es la página JSF:

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"    
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:ui="http://java.sun.com/jsf/facelets">
    <h:head>
        <ui:insert name="header">           
            <ui:include src="header.xhtml"/>         
        </ui:insert>
    </h:head>
    <h:body>

        <h1><img src="resources/css/images/icon.png" alt="NVIDIA.com" /> History Center</h1>
        <!-- layer for black background of the buttons -->
        <div id="toolbar" style="margin: 0 auto; width:1180px; height:30px; position:relative;  background-color:black">
            <!-- Include page Navigation -->
            <ui:insert name="Navigation">           
                <ui:include src="Navigation.xhtml"/>         
            </ui:insert>

        </div>  

        <div id="logodiv" style="position:relative; top:35px; left:0px;"> 
            <h:graphicImage alt="Demo Insert Form"  style="position:relative; top:-20px; left:9px;"  value="resources/images/logo_databasez.png" />
        </div>
        <div id="main" style="margin: 0 auto; width:1190px; height:700px; position:absolute;  background-color:transparent; top:105px">

            <div id="mainpage" style="margin: 0 auto; width:1190px; height:500px; position:absolute;  background-color:transparent; top:80px">

                <div id="settingsHashMap" style="width:350px; height:400px; position:absolute;  background-color:r; top:20px; left:1px">
                    <h:form>
                        <div id="settingsdiv" style="width:750px; height:400px; position:absolute;  background-color:r; top:20px; left:1px">

                            <h:panelGrid columns="2">
                                <h:panelGroup>Session ID</h:panelGroup>
                                <h:panelGroup>
                                    <h:inputText id="sessionid" value="#{DatabaseController.formMap['sessionid']}" >
                                        <f:validateLength minimum="0" maximum="15"/>
                                        <f:ajax render="sessionidvalidate" event="blur"/>                                          
                                    </h:inputText>
                                    <h:outputText id="sessionidvalidate" rendered="#{DatabaseController.validateSessionid}" value="session is already registered" />
                                </h:panelGroup>

                                <h:panelGroup>User ID</h:panelGroup>
                                <h:panelGroup>
                                    <h:inputText id="userid" value="#{DatabaseController.formMap['userid']}" >
                                        <f:validateLength minimum="0" maximum="15"/>
                                    </h:inputText>
                                </h:panelGroup>

                                <h:panelGroup>Login Time</h:panelGroup>
                                <h:panelGroup>
                                    <h:inputText id="logintime" value="#{DatabaseController.formMap['logintime']}" >
                                        <f:validateLength minimum="0" maximum="35"/>
                                    </h:inputText>
                                </h:panelGroup>

                                <h:panelGroup>Last Refresh Time</h:panelGroup>
                                <h:panelGroup>
                                    <h:inputText id="lastrefreshtime" value="#{DatabaseController.formMap['lastrefreshtime']}" >
                                        <f:validateLength minimum="0" maximum="35"/>
                                    </h:inputText>
                                </h:panelGroup>

                                <h:panelGroup>User IP</h:panelGroup>
                                <h:panelGroup>
                                    <h:inputText id="userip" value="#{DatabaseController.formMap['userip']}" >
                                        <f:validateLength minimum="0" maximum="15"/>
                                    </h:inputText>
                                </h:panelGroup>

                            </h:panelGrid>          

                        </div>   

                        <div id="settingstwodiv" style="width:150px; height:60px; position:absolute;  background-color:transparent; top:380px; left:800px">

                            <h:commandButton value="Create User" action="#{DatabaseController.saveData}"/>

                        </div> 
                    </h:form> 

                </div>   

            </div>  
        </div>

    </h:body>
</html>

Este es el bean gestionado:

import java.io.Serializable;
import javax.enterprise.context.SessionScoped;
// or import javax.faces.bean.SessionScoped;
import javax.inject.Named;
/* include SQL Packages */
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.HashMap;
import javax.annotation.PostConstruct;
import javax.sql.DataSource;
import javax.annotation.Resource;
import javax.faces.context.FacesContext;
import javax.inject.Inject;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
// or import javax.faces.bean.ManagedBean;   

import org.glassfish.osgicdi.OSGiService;

// Demo Insert Form
@Named("DatabaseController")
@SessionScoped
public class Database implements Serializable {

    private HashMap<String, String> formMap = new HashMap<>();

    public Database() {
    }
    /* Call the Oracle JDBC Connection driver */
    @Resource(name = "jdbc/Oracle")
    private DataSource ds;

    public HashMap<String, String> getformMap() {
        return formMap;
    }

    /*

    CREATE TABLE ACTIVESESSIONS(
    SESSIONID VARCHAR2(30 ) NOT NULL,
    USERID VARCHAR2(30 ) NOT NULL,
    LOGINTIME TIMESTAMP(6),
    LASTREFRESHTIME TIMESTAMP(6),
    USERIP VARCHAR2(30 )
    )
    /
     */
    @PostConstruct
    public void hashMapGenerate() {
        /* Initialize the hashmap */
        formMap.put("sessionid", null);
        formMap.put("userid", null);
        formMap.put("logintime", null);
        formMap.put("lastrefreshtime", null);
        formMap.put("userip", null);
    }

    public int saveData() throws SQLException, java.text.ParseException {
//        formMap = new HashMap<String, String>();

        String SqlStatement = null;

        if (ds == null) {
            throw new SQLException();
        }

        Connection conn = ds.getConnection();
        if (conn == null) {
            throw new SQLException();
        }

        PreparedStatement ps = null;

        /*

        CREATE TABLE ACTIVESESSIONS(
        SESSIONID VARCHAR2(30 ) NOT NULL,
        USERID VARCHAR2(30 ) NOT NULL,
        LOGINTIME TIMESTAMP(6),
        LASTREFRESHTIME TIMESTAMP(6),
        USERIP VARCHAR2(30 )
        )
        /
         */

        try {
            conn.setAutoCommit(false);
            boolean committed = false;
            try {           /* insert into Oracle the default system(Linux) time */
                SqlStatement = "INSERT INTO ACTIVESESSIONS"
                        + " (SESSIONID, USERID, LOGINTIME, LASTREFRESHTIME, USERIP)"
                        + " VALUES (?, ?, ?, ?, ?)";

                ps = conn.prepareStatement(SqlStatement);

                ps.setString(1, formMap.get("sessionid"));
                ps.setString(2, formMap.get("userid"));
                ps.setTimestamp(3, toTimeStamp(formMap.get("logintime")));
                ps.setTimestamp(4, toTimeStamp(formMap.get("lastrefreshtime")));
                ps.setString(5, formMap.get("userip"));

                ps.executeUpdate();

                conn.commit();
                committed = true;
            }
            finally 
            {
                if (!committed) {
                    conn.rollback();
                }
            }
        } finally {
            /* Release the resources */
            ps.close();
            conn.close();
        }

        return 0;

    }
    private Timestamp toTimeStamp(String s) throws java.text.ParseException
    {
        Timestamp ts = null;
        java.util.Date date = null;
        if (s == null || s.trim().isEmpty()) return ts;

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.S");
        date = (java.util.Date) sdf.parse(s);
        ts = new Timestamp(date.getTime());

        return ts;

    }

    /* Validators section */
    public boolean getvalidateSessionid(){

        //do SQL query

        return true;
    }

}

Estoy teniendo dificultades para implementar la validación de formularios. Quiero pasar el String introducido por el usado y registrarlo en la base de datos si este valor ya está en la tabla de la base de datos. Aquí estoy llamando al método Java para verificar el valor:

                            <h:panelGroup>
                                <h:inputText id="sessionid" value="#{DatabaseController.formMap['sessionid']}" >
                                    <f:validateLength minimum="0" maximum="15"/>
                                    <f:ajax render="sessionidvalidate" event="blur"/>                                          
                                </h:inputText>
                                <h:outputText id="sessionidvalidate" rendered="#{DatabaseController.validateSessionid}" value="session is already registered" />
                            </h:panelGroup>

¿Cómo puedo enviar el valor insertado al método Java?

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