@Entity
@Table(name="Anfrage", schema="dbo", catalog="ReqManager")
public class Anfrage implements java.io.Serializable {
    ...
    private Beleg beleg;
    ...
    @ManyToOne(fetch=FetchType.LAZY, cascade=CascadeType.ALL)
    @JoinColumn(name="BelegID", nullable=false)
    public Beleg getBeleg() {
        return this.beleg;
    }
    
    public void setBeleg(Beleg beleg) {
        this.beleg = beleg;
    } 

@Entity
@Table(name="Beleg", schema="dbo", catalog="ReqManager"(
public class Beleg implements java.io.Serializable {
    ...

@Component
public class BelegValidator implements Validator {
    @Override
    public boolean supports(Class<?> type) {
        return type == Beleg.class;
    }

    @Override
    public void validate(Object o, Errors errors) 
    ....

@Component
public class AnfrageValidator implements Validator {
    ...
    @Autowired private BelegValidator belegValidator;
    ...
    @Override
    public boolean supports(Class<?> type) {
        return type == Anfrage.class;
    }

    @Override
    public void validate(Object o, Errors errors) {
        ....
        if (anfrage.getBeleg() != null) {
            //Это все для теста - все проходит хорошо
            if (belegValidator == null) {
                throw new IllegalArgumentException("The supplied belegValidator is required and must not be null.");
            }
            if (!belegValidator.supports(Beleg.class)) {
                throw new IllegalArgumentException("The supplied belegValidator must support the validation of [Address] instances.");
            }
            
            try {
                errors.pushNestedPath("beleg");
                //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
                ValidationUtils.invokeValidator(belegValidator, anfrage.getBeleg(), errors);
                //!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
            } finally {
                errors.popNestedPath();
            }
        }
    ....

    @Override
    public boolean supports(Class<?> type) {
        return type == Beleg.class;
    }

    @Override
    public boolean supports(Class<?> type) {
        return type == Beleg.class || type.getSuperclass().getSimpleName().equalsIgnoreCase("Beleg");
    }