由于web中的文件不能直接通过url方式读取opencms的sites下的文件，所以必须绕个弯子解决。查阅了一下opencms的源代码，我的解决思路如下：

 

第一 拷贝方式：

 

   1.第一次访问时，根据opencms提供的接口，把文件从数据库读到java对象obj

   2.将obj对象拷贝到web中的对应目录

   3.将web中的对应目录的url确定，即可直接调用。

   4.第二次及其以后访问时，根据对象obj的最后修改时间属性，确定是否需要重复1-3步骤。

参考源代码：
 

  <% @ page pageencoding = " utf-8 "   %>
<% @ page buffer = " none "   import = " org.opencms.util.*, org.teema.eeonline.exhibition.exhibitionconstants,com.tblink.common.util.stringutil,org.opencms.frontend.templateone.modules.*,javax.servlet.servletoutputstream, org.opencms.file.*,java.util.*, java.io.*, org.opencms.frontend.templateone.* "   %>
<% @ taglib uri = " http://jakarta.apache.org/struts/tags-bean "  prefix = " bean " %>
<% @ taglib prefix = " cms "  uri = " http://www.opencms.org/taglib/cms "   %>
<% @ taglib prefix = " fmt "  uri = " http://java.sun.com/jstl/fmt "   %>
<% @ taglib prefix = " c "  uri = " http://java.sun.com/jstl/core "   %>
<% @ include file = " ../elements/common/common.jsp "   %>

<%!
private  string copyfile(cmsfile cmsfile){
     try {
         byte [] bytefile  =  cmsfile.getcontents();
        string path  =  stringutil.getrealpath(stringutil. class , " web-inf " ,exhibitionconstants.exhibition_flash_directionary);
        randomaccessfile rf = new  randomaccessfile(path   exhibitionconstants.exhibition_flash_name, " rw " ); 
        rf.write(bytefile); 
        rf.close();
         return  path.substring( 0 ,path.length() - 1 );
    }
     catch (exception e)
    {
         return   "" ;
    }
}
%>

<%
string direct  =  exhibitionconstants.exhibition_flash_directionary   exhibitionconstants.exhibition_flash_name;
string flashurl  =   "" ;
try {
cmsfile cmsfile  =  __cmsjsp.getcmsobject().readfile(direct);
long  l  =  cmsfile.getdatelastmodified();
string lstr  =  (string)application.getattribute(exhibitionconstants.application_flash_date_index);
flashurl  =  (string)application.getattribute(exhibitionconstants.application_flash_url_index);

if (lstr == null   ||   ! stringutil.isnums(lstr)){
    direct  =  copyfile(cmsfile);
} else   if (long.parselong(lstr) == l){
     if (flashurl == null ){
        direct  =  copyfile(cmsfile);
    }
} else {
      direct  =  copyfile(cmsfile);
}
flashurl  =   request.getcontextpath()   exhibitionconstants.exhibition_flash_directionary   exhibitionconstants.exhibition_flash_name;
application.setattribute(exhibitionconstants.application_flash_date_index,lstr);
application.setattribute(exhibitionconstants.application_flash_url_index,flashurl);

}
catch (exception e)
{
    out.println(e); 
}
%>

< object classid = " clsid:d27cdb6e-ae6d-11cf-96b8-444553540000 "  codebase = " http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0 "  width = " 760 "  height = " 266 " >
        < param name = " movie "  value = " <%=flashurl%> " >
        < param name = " quality "  value = " high " >
        < embed src = " <%=flashurl%> "  quality = " high "  pluginspage = " http://www.macromedia.com/go/getflashplayer "  type = " application/x-shockwave-flash "  width = " 760 "  height = " 266 " > embed >
object >