dwr Illegal access to default constructor错误

dwr.xml:
<create creator="struts" javascript="PrisonerActionForm">
  <param name="formBean" value="prisonerForm"/>
  <include method="setPrisonerValue"/>
  </create>
  <convert converter="bean" match="com.bizlogic.prisons.prisoner.Prisoner" />
调用：
PrisonerActionForm.setPrisonerValue(list);
dwr报错Illegal access to default constructor，请高手帮忙解决．在线等．

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帮下忙呀。

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等高手来帮忙呀．