如何在EJB3（JPA）和Hibernate中获取@Id注解的字段？

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    // 其他字段和getter、setter方法
}

import java.lang.reflect.Field;
import javax.persistence.Id;

public static String getIdFieldName(Class<?> entityClass) {
    Field[] fields = entityClass.getDeclaredFields();
    for (Field field : fields) {
        if (field.isAnnotationPresent(Id.class)) {
            return field.getName();
        }
    }
    return null;
}

String idFieldName = getIdFieldName(User.class);
System.out.println("主键字段名称：" + idFieldName);