ireport子报表有关问题，各位帮帮忙

   <result name="fwjcprint" type="jasper">
               <param name="location">/jasper/fwjcdReport.jasper</param>
               <param name="format">HTML</param>
               <param name="dataSource">bcpjcdVoList</param>
    </result>

两个JAVABEAN
//主表的数据源
public class BcpjcdVo{
    private String jcdid;
    ......
    List<BcpjcdmxVo> bcpjcdmxList;

.....}

//子报表的数据源
public class BcpjcdmxVo{
    private String mxid;
    private String bcpmc;
    .....}

public String printUI(){
    ......
        String jcdid = ServletActionContext.getRequest().getParameter("jcdid");
        BcpjcdVo jcdVo = fwjcdDaoJDBC.queryBcpjcdByJcdid(jcdid);
        List<BcpjcdmxVo> bcpjcdmxVo = fwjcdDaoJDBC.queryBcpjcdMxByJcdid(jcdid);
        
        ServletActionContext.getRequest().setAttribute("jcdmxList", bcpjcdmxVo );
        jcdVo.setBcpjcdmxList(ycljcdmxVo);//当我设置时就会报错，不设时就没有问题
        
        this.setBcpjcdVo(jcdVo);
        ......
        

        return FWJCPRINT;
    }