原文地址：http://jhyimu2005.javaeye.com/blog/514379
先声明一下我用的框架是Spring + Hibernate + SpringMVC 数据库使用的是Oracle
昨天遇到了一个特诡异的问题就是我使用Oracle序列，把主键的计数交给Hibernate处理， Entity @Table(name = "BIO_STUDY") public class Study implements Serializable{ private static final long serialVersionUID = -5932941248053882057L; private int id; private Project project; private String name; private String description; private Set<Experiment> experiments; @Id @Column(name = "ID") @SequenceGenerator(name = "BIO_STUDY_SQ", sequenceName = "BIO_STUDY_SQ" ) @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "BIO_STUDY_SQ") public int getId() { return id; }

写完部署什么都没问题，可当我写了测试类进行测试时发现主键的初始值竟然是50，其步长亦是50，在同事的帮助下发现原来是Hibernate在做鬼，@SequenceGenerator中添加两个参数（allocationSize = 1, initialValue = 1）就OK。通过查找Hibernate的资料发现原来是因为allocationSize的默认值是50.具体请参考http://www.oracle.com/technology/global/cn/products/ias/toplink/jpa/resources/toplink-jpa-annotations.html#SequenceGenerator

只需要增加allocationSize = 1就可以