Angular POST RESTful API to Ejb resulting in 404 not found error

I was having some problem when trying to send RESTful API from Angular to EJB. Here is my component.ts:

this.opUserAdminWinService.retrievePegRoleList().subscribe(resf => {
        console.log(resf);
});

And my service.ts:

serviceAPI = SERVER_API_URL;
mainAPI = '/api/securityactivity/securityactivity';
retrievePegRoleList() {
    const url: string = this.serviceAPI + this.mainAPI + '/RetrievePegRoleList';
    return this.http.post(url, this.httpOptions);
}

In my Controller.java:

@PostMapping("/RetrievePegRoleList")
public Vector RetrievePegRoleList()
    throws JaMClientRemoteException, JaMException {
    return getSecurityActivity().RetrievePegRoleList();
}

In my EjbBean class:

public Vector RetrievePegRoleList() throws JaMClientRemoteException, JaMException;

@TransactionAttribute(TransactionAttributeType.SUPPORTS)
public Vector RetrievePegRoleList() throws JaMClientRemoteException, JaMException
{
    Vector pegRoleList;
    try {
        String dataSource = JaM.getProperties().ORD_DATA_SOURCE;
        RetrievePegRoleListTask retrievePegRoleListTask = new RetrievePegRoleListTask(dataSource);
        retrievePegRoleListTask.execute();
        pegRoleList = retrievePegRoleListTask.getResult();
    } catch (Exception e) {
        throw new JaMClientRemoteException(this.ERR_EXCEPTION_JAM, e.toString());
    }
    return pegRoleList;
}

However, I am getting this error message:

enter image description here

Any ideas why is it so? Thanks!

Source: New feed
Source Url Angular POST RESTful API to Ejb resulting in 404 not found error