utiliser des Types personalisés

bonjour
je travail sur un projet où je dois créer et consommer des web services CRUD (avec hibernate) mais le problème réside quand je veux récupérer par exemple une list de projet (type projet)

je vous donne le message d'erreur et le code de la class projet

message d'erreur:

21:30:16,296 ERROR [InvokerProviderJSE] Error from service endpoint, processing
fault handler chain
java.lang.ClassCastException: java.util.ArrayList
at project.CrudProject.listProject(CrudProject.java:49)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)

Code de la classe de persistance :

package project.types;

import java.io.Serializable;

public class ProjectType implements Serializable {

/**
*
*/
private static final long serialVersionUID = 3936072504804316631L;
private Integer idProject;
private String nameProject;
private String dateDebutProject;
private String dateFinProject;

public ProjectType() {
super();
}

public ProjectType(Integer idProject, String nameProject,
String dateDebutProject, String dateFinProject) {
super();
this.idProject = idProject;
this.nameProject = nameProject;
this.dateDebutProject = dateDebutProject;
this.dateFinProject = dateFinProject;
}

public Integer getIdProject() {
return idProject;
}
public void setIdProject(Integer idProject) {
this.idProject = idProject;
}
public String getNameProject() {
return nameProject;
}
public void setNameProject(String nameProject) {
this.nameProject = nameProject;
}
public String getDateDebutProject() {
return dateDebutProject;
}
public void setDateDebutProject(String dateDebutProject) {
this.dateDebutProject = dateDebutProject;
}
public String getDateFinProject() {
return dateFinProject;
}
public void setDateFinProject(String dateFinProject) {
this.dateFinProject = dateFinProject;
}

}