Problemas persistencia no hibertnate quando deletar ou incluir uma linha

HTTP Status 500 - 

--------------------------------------------------------------------------------

type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

javax.servlet.ServletException: Servlet execution threw an exception


root cause 

java.lang.NoClassDefFoundError: org/hibernate/cfg/AnnotationConfiguration
	Controlador.ExcluirServlet.doGet(ExcluirServlet.java:23)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


root cause 

java.lang.ClassNotFoundException: org.hibernate.cfg.AnnotationConfiguration
	org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1647)
	org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1493)
	Controlador.ExcluirServlet.doGet(ExcluirServlet.java:23)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

<!DOCTYPE hibernate-configuration PUBLIC
		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
		"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
	<session-factory>
		<property name="hibernate.dialect">	org.hibernate.dialect.MySQLDialect</property>
		<property name="hibernate.connection.driver_class">	com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.url">jdbc:mysql://localhost/testehib</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password"></property>
		<property name="hibernate.connection.pool_size">10</property>		
		<property name="hibernate.show_sql">true</property>	
		<property name="hibernate.connection.autocommit">true</property>		
		<property name="hibernate.hbm2ddl.auto"></property>		  
		<mapping class="Persistencia.Cadastro"/>
    </session-factory>
</hibernate-configuration>

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		SessionFactory sf = (new AnnotationConfiguration().configure("/CFG/hibernate.cfg.xml")
				.buildSessionFactory());
		Session sessao = sf.openSession();
		
		Transaction tx = null;
		
		
			tx = sessao.beginTransaction();
			
			Cadastro cad = new Cadastro();
			
			cad.setId(2);
			
			sessao.delete(cad);
			tx.commit();
	
	}

@Entity
public class Cadastro {
	@Id
	@GeneratedValue
	private int id;
	@Column(name="nome")
	private String nome;
	@Column(name="email")
	private String email;
	@Column(name="idade")
	private int idade;
	public int getId() {
		return id;

       //setters e getters...