hibenate 无法插入，能删除

错误如下：
type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.springframework.dao.InvalidDataAccessResourceUsageException: could not insert: [entitle.Time2]; nested exception is org.hibernate.exception.SQLGrammarException: could not insert: [entitle.Time2]
org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:630)
org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:424)
org.springframework.orm.hibernate3.HibernateTemplate.executeWithNativeSession(HibernateTemplate.java:374)
org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:694)
dao.TimeDaoImpl.insert(TimeDaoImpl.java:22)
biz.TimeBizImpl.insert(TimeBizImpl.java:19)
action.TimeAction.insert(TimeAction.java:24)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

daoimpl如下：
public void insert(Time2 time) {
    // TODO Auto-generated method stub
    System.out.println("insert.dao");
    System.out.println("long:"+time.getLong_());
    super.getHibernateTemplate().save(time);
    //super.getHibernateTemplate().delete(time);
}


实体类如下：
public class Time2 implements java.io.Serializable {

// Fields

private Integer id;
private String long_;

数据库是mysql，，id为自增
能执行删除操作，可是新增操作就出错，，求助，谢谢。

这个Time2怎么看起来这么别扭。
hibenate 中你设置主键生成策略是什么呢？

dao.TimeDaoImpl.insert(TimeDaoImpl.java:22) 22行是什么？？打断点看看