有关ibatis求助
请哪位高手看一下，错在哪里了

public void updateChannel(Channel c) {

		try {

			session.update(Channel.class.getName()+".updateChannel", c);

			session.commit();

		} catch (Exception e) {

			e.printStackTrace();

			session.rollback();

		} finally{

			session.close();

		}

}

配置文件

	<update id="updateChannel" parameterType="Channel" >

		update t_channel set name=#{name},description=#{description} where id=#{id}

	</update>

junit测试

	@Test

	public void testUpdateChannel() {

		Channel c = channeldao.getChannelById(11);

		c.setName("updatechannel");

		channeldao.updateChannel(c);

	}

出现的错误--------------------------------------------------
org.apache.ibatis.exceptions.PersistenceException: 
### Error updating database.  Cause: org.apache.ibatis.executor.ExecutorException: Executor was closed.
### The error may exist in com/test/cms/backmanager/DAO/implement/Channel.xml
### The error may involve com.test.cms.model.Channel.updateChannel
### The error occurred while executing an update
### Cause: org.apache.ibatis.executor.ExecutorException: Executor was closed.
at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:8)
at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:123)
at com.test.cms.backmanager.DAO.implement.ChannelDaoForMybatisImpl.updateChannel(ChannelDaoForMybatisImpl.java:89)
at com.test.cms.backmanager.DAO.ChannelDAOTest.testUpdateChannel(ChannelDAOTest.java:55)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:73)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:46)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:180)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:41)
at org.junit.runners.ParentRunner$1.evaluate(ParentRunner.java:173)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
at org.junit.runners.ParentRunner.run(ParentRunner.java:220)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)