hibernate往mysql中插入数据

	    	System.out.println(functionTable.getFt_describe()  +  "    " + functionTable.getFt_id() + "   " + functionTable.getFt_name() + "    " + functionTable.getFt_page());

			session.save(functionTable);

functionTable是一个类的对象有四个属性，对应数据库中的四个字段。通过输出在保存之前输出打印四个属性值，都有值。
但执行到save方法时就出错了
异常：
0    F0111   sfefse    fsfef
Hibernate: insert into functiontable (ft_name, ft_describe, ft_page) values (?, ?, ?)
2011-08-11 08:48:44 [org.hibernate.util.JDBCExceptionReporter]-[WARN] SQL Error: 1364, SQLState: HY000 -(71)
2011-08-11 08:48:44 [org.hibernate.util.JDBCExceptionReporter]-[ERROR] Field 'ft_id' doesn't have a default value -(72)
org.hibernate.exception.GenericJDBCException: could not insert: [edu.usc.vo.Functiontable]
at org.hibernate.exception.ErrorCodeConverter.handledNonSpecificException(ErrorCodeConverter.java:92)
at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:80)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:1777)
at org.hibernate.persister.entity.BasicEntityPersister.insert(BasicEntityPersister.java:2178)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:34)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:239)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:240)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:160)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:95)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:184)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:173)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:69)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:481)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:476)
at edu.usc.dao.impl.FunctionDAO.addFunctionTable(FunctionDAO.java:75)
at edu.usc.Test.RoleActionTest.testPreQueryRoleAction(RoleActionTest.java:39)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99)
at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75)
at org.junit.internal.runners.TestMethodRunner.run(