How to use ReplacementDataSet ?

[SuperNoobTao]

Hello:
I have problem when I use 'spring-test-dbunit' in my project->
For example : in my 'datasets.xml' , a column is null ,so I set it to [null] , but it was not work and
throw error.
I don not know how to use 'ReplacementDataSet' in my testcase.
Can u help me ? very thx!!