ajax4jsf
我在做一个网站，用的是MyFaces，还用到了Ajax4JSF。但是原来用JSP实现的文件下载功能就不好使了，出现下面的异常，请问是怎么回事呀？怎么改正呢？
java.lang.IllegalStateException:   Servlet   response   already   use   stream,   Writer   not   possible
at   org.ajax4jsf.framework.ajax.xmlfilter.FilterServletResponseWrapper.getWriter(FilterServletResponseWrapper.java:220)
at   org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:124)
at   org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:117)
at   org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:191)
at   org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:115)
at   org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:75)
at   org.apache.jsp.pages.download_jsp._jspService(download_jsp.java:216)
at   org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at   javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at   org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
at   org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
at   org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
at   javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at   org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at   org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at   org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672)
at   org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463)
at   org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398)
at   org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
at   org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:416)
at   org.apache.myfaces.application.jsp.JspViewHandlerImpl.renderView(JspViewHandlerImpl.java:234)
at   org.ajax4jsf.framework.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:108)
at   org.ajax4jsf.framework.ajax.AjaxViewHandler.renderView(AjaxViewHandler.java:229)
at   org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:384)
at   javax.faces.webapp.FacesServlet.service(FacesServlet.java:138)
at   org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at   org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at   org.ajax4jsf.framework.ajax.xmlfilter.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:96)
at   org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:220)
at   org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at   org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at   cn.com.pbi.netmgr.web.morning.ExceptionFilter.doFilter(ExceptionFilter.java:55)
at   org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at   org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at   org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:144)
at   org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appli