POI导出Excel表格异常：cannot call getWriter() after getOutputStream()

开发环境的服务器是Tomcat，测试环境的服务器是WebLogic。开发导出功能选用组件POI，同时想在用户导出数据时同时弹出导出框，让用户自由选择下载位置。在Tomcat环境下导出数据时没有问题， WebLogic环境下测试发现导出数据抛异常。
异常信息： java.lang.IllegalStateException: strict servlet API: cannot call getWriter() after getOutputStream()
异常代码写法如下：

//导出
String fileName = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date()) +".xls";
response.setContentType("application/vnd.ms-excel; charset=utf-8");
response.setHeader("Content-Disposition", "attachment;fileName="+fileName);
response.setCharacterEncoding("utf-8");
wb.write(response.getOutputStream());

追其原因，网上有说两者不能同时使用，也有说是weblogic的问题

连接地址1
连接地址2
连接地址3
连接地址4

最终解决方案

/**
 * 导出Excel
 */
@RequestMapping("/exportExcel")
public String exportExcel(HttpServletRequest request, HttpServletResponse response) throws Exception{

    //获取查询条件
    Map paramMap = this.getRequestParamMap(request);

    //定义表的标题
    String[] header = {"序号","ID","姓名","性别","年龄","地址"};

    //定义表的内容
    List contentsList = service.getExportData(paramMap);

    //导出Excel
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    try {
        Workbook wb = excelUtil.getWorkbook(header, contentsList);
        wb.write(os);
    } catch (Exception e) {
        e.printStackTrace();
    }

    byte[] content = os.toByteArray();
    InputStream is = new ByteArrayInputStream(content);

    //设置response参数，可以打开下载页面
    response.reset();
    response.setContentType("application/vnd.ms-excel; charset=utf-8") ;
    response.setHeader("Content-Disposition", "attachment; filename=" + excelUtil.getFileName());

    ServletOutputStream out = response.getOutputStream();
    BufferedInputStream bis = null;
    BufferedOutputStream bos = null;
    try {
        bis = new BufferedInputStream(is);
        bos = new BufferedOutputStream(out);

        byte[] buff = new byte[2048];
        int bytesRead;

        while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {
            bos.write(buff, 0, bytesRead);
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        if (bis != null)
            bis.close();
        if (bos != null)
            bos.close();
    }

    return null;                            
}

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