postgreSQL&hibernate整合实现主键自增

这个错误是咋回事勒，第一次使用postgreSQL，与hibernate整合，实现userid自增,结果出错了

this.getHibernateTemplate().save(userInfo);

Console显示结果Hibernate: select max(userid) from UserInfo

jsp页面显示错误

org.springframework.dao.InvalidDataAccessResourceUsageException: could not fetch initial value for increment generator; nested exception is org.hibernate.exception.SQLGrammarException: could not fetch initial value for increment generator
	org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:615)
	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:690)
	com.test.dao.impl.UserDAOImpl.saveUser(UserDAOImpl.java:33)
	com.test.service.impl.UserServiceImpl.save(UserServiceImpl.java:51)
	com.test.action.user.SaveUserAction.execute(SaveUserAction.java:39)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	java.lang.reflect.Method.invoke(Method.java:597)
	com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:440)
	com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:279)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
	com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:163)
	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
	com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:249)
	org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
	com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:122)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
	com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
	com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:195)
	com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:87)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:236)
	com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.j