enable XML validation in tomcat

salamo 3likom i have deployed my web  Application using tomcat 5

 it works well  but after that i added ajax validation part into my project  but it doesn't work i notices when i start the server that xml validation disabled  , then i enabled it but it gave me an error message  , i searched for solution and i found that the tomcat dun have xml parser  so what can i do or how

ahmed adel 0103840145