JSF 将模板渲染为文本/纯文本答案

【问题标题】：JSF render template to text/plainJSF 将模板渲染为文本/纯文本
【发布时间】：2016-06-24 02:02:48
【问题描述】：

我有一个（工作的）JSF 应用程序。现在我希望使用 JSF 表达式语言扩展一个不是页面资源的文档（假设是纯文本文档）（因为我需要来自我的 bean 的状态，这看起来很“自然”）。但似乎我没有完全了解机制......

为了处理“*.txt”文件（如果 web.xml 中有）

<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
</servlet-mapping> 
<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.txt</url-pattern>
</servlet-mapping>

我添加了一个“plain.txt”资源

<f:view contentType="text/plain" xmlns:f="http://java.sun.com/jsf/core" >

hi #{request.contextPath}/

</f:view>

请求

http://myServer/myApp/plain.txt

在使用 myfaces 2.1.10 的服务器上因无限循环而失败。将资源重命名为“plain.xhtml”并请求它工作正常。

更新到 myfaces 2.1.17（在 2.2.9 上相同）后，提供“plain.txt”也有效！

问题是：以这种方式使用模板是“最佳实践”还是“意外的副作用”（并且不应该真正起作用）？有没有更好的方法来实现这样的模板任务？

编辑

经过更多尝试，它似乎更加奇怪。提供扩展内容似乎随机失败（2.1.17 和 2.2.9）。重新启动后，我在服务器端获得了一个资源“res1.txt”的“循环”，但不是资源“res2.txt”的精确副本。还发生了“res1.txt”成功呈现。也许服务器跟踪可以提供一些提示：

首先，有一个很长的“递归”

Mär 09, 2016 5:06:20 PM org.apache.catalina.core.ApplicationDispatcher invoke
SCHWERWIEGEND: Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
    at org.apache.myfaces.shared.context.flash.FlashImpl.isKeepMessages(FlashImpl.java:388)
    at org.apache.myfaces.shared.context.flash.FlashImpl._saveMessages(FlashImpl.java:668)
    at org.apache.myfaces.shared.context.flash.FlashImpl.doPostPhaseActions(FlashImpl.java:269)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:254)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:486)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:411)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:338)
    at org.apache.myfaces.context.servlet.ServletExternalContextImpl.dispatch(ServletExternalContextImpl.java:369)
    at org.apache.myfaces.view.jsp.JspViewDeclarationLanguage.buildView(JspViewDeclarationLanguage.java:99)
    at org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:78)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:241)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

这条轨迹不断重复，每次都变短，直到最终到达这个终点：

Mär 09, 2016 5:06:20 PM org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet [Faces Servlet] in context with path [/cloudsuite-snippets] threw exception
java.lang.NullPointerException
    at org.apache.myfaces.shared.context.flash.FlashImpl.isKeepMessages(FlashImpl.java:388)
    at org.apache.myfaces.shared.context.flash.FlashImpl._saveMessages(FlashImpl.java:668)
    at org.apache.myfaces.shared.context.flash.FlashImpl.doPostPhaseActions(FlashImpl.java:269)
    at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:254)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:199)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

浏览器页面只是白色的..

编辑二

还有另一个信息：失败并不是真正的不确定性（这会稍微损害我的信仰......）但仍然很奇怪。对于我有同名资源但结尾为“.xhtml”的所有资源，渲染成功。

服务器似乎在内部重定向到“.xhtml”版本，渲染这个内容并以“.txt”版本的名称返回它（忽略后者的内容）。这是怎么回事？

【问题讨论】：

标签： jsf text-files infinite-loop myfaces servlet-mapping

【解决方案1】：

问题是：以这种方式使用模板是“最佳实践”还是“意外的副作用”（并且不应该真正起作用）？

它不应该真的起作用。 JSF 作为基于 HTML 表单的 MVC 框架首先不支持 text/plain 内容，而仅支持基于 HTML 的内容，例如 text/html。在 Mojarra 而不是 MyFaces 上尝试您的用例时（在将 plain.txt 重命名为 plain.xhtml 后，请参见下文），我得到以下异常：

java.lang.IllegalArgumentException：无法识别的内容类型。

关于视图解析，从技术上讲，您应该将您的 plain.txt 文件命名为 plain.xhtml，并且只将 *.txt URL 模式添加到 FacesServlet。 FacesServlet 即在将 URL 模式中的任何文件扩展名重新映射到默认为 .xhtml 的上下文参数 javax.faces.DEFAULT_SUFFIX 后定位物理视图。当物理文件不存在时，JSF 将从 Facelets 视图回退到 JSP 视图（通过堆栈跟踪中存在 JspViewDeclarationLanguage 来确认）但由于 plain.jsp 也不存在并且 URL 仍然与 FacesServlet 匹配映射它反过来在无限循环中运行，试图寻找和渲染物理资源是徒劳的。

有关 JSF 视图解析的内部工作原理的详细说明，另请参阅 JSF Facelets: Sometimes I see the URL is .jsf and sometimes .xhtml. Why? 关于 dispatch() 上的无限循环，这在技术上又是 JSF 中的一个错误，因为它实际上应该返回 404。

有没有更好的方法来实现这样的模板任务？

如果唯一的目的是评估 EL 表达式，那么最好使用 JSP servlet 而不是 JSF servlet，并专门使用只读 EL 表达式 ${} 而不是可写 EL 表达式 #{}，因为 JSP 不支持这一点。

最简单的方法是将 servlet 名称更改为 Tomcat 自己的 JSP servlet 之一：jsp（<servlet> 条目不是必需的，因为 Tomcat 已经在自己的 /conf/web.xml 中定义了它。

<servlet-mapping>
    <servlet-name>jsp</servlet-name>
    <url-pattern>*.txt</url-pattern>
</servlet-mapping>

然后将/plain.txt 更改为JSP 视图，如下所示。注意 ${request} 在 JSP 中不存在，它只能作为 ${pageContext} 的属性使用。另见our EL wiki page。

<%@page contentType="text/plain" %>

hi ${pageContext.request.contextPath}/

关于解析托管bean，它只是不发现JSF@ManagedBean，但它可以发现CDI@Named。因此，当您install CDI on Tomcat 并将感兴趣的托管 bean 改造成 CDI 托管 bean 而不是 JSF 托管 bean 时，它们将可用。

一个不同的替代方案需要更多的工作，但保证跨 servlet 容器可移植（因为jsp 的 servlet 名称是 Tomcat 特定的，尽管几乎所有 servlet 容器都具有相同的“事实上”名称）使用普通的 vanilla servlet甚至可能是您想到的任务的 JAX-RS (RESTful) 资源。将其映射到所需的/plain.txt 的 URL 模式，让它准备所需的模型，最后转发到“真实的”JSP 文件the usual way。

@WebServlet("/plain.txt")
public class PlainTxtServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.getRequestDispatcher("/WEB-INF/plain.jsp").forward(request, response);
    }

}

并且有一个/WEB-INF/plain.jsp 作为物理文件，仍然使用上面提到的JSP 语法。请注意，它位于/WEB-INF 内，因为您不希望最终用户能够直接请求/plain.jsp 而不是/plain.txt。

额外的好处是这并不一定需要 CDI 来管理 bean，因为您可以手动管理 bean，如下所示：

Bean bean = new Bean();
request.setAttribute("bean", bean);

它将在 EL 中以 ${bean} 的形式提供。

另见：

【讨论】：

一如既往的合理、深入和清晰的分析。感谢您和您在本网站所做的宝贵贡献。
澄清一下：映射到扩展名 .txt 是请求的 hack 的一部分。在现实世界中，我们谈论的是动态 .jnlp，并且以不那么明显的方式，不同的平台、浏览器和安全设置启动此文件，“下载”时正确的扩展名很重要。如果将这种快速而肮脏的“挤压”到 JSF 中是不正确的，我将恢复为干净的 JaxRS 解决方案。如果我无论如何都要编码，也许基于另一个模板引擎（freemarker）......
我认为普通的 Servlet(+JSP) 最适合这项工作，因为 JAX-RS 暗示了一个“Web 服务”API，它以 XML/JSON/CSV/etc 的形式返回一个或多个实体，而不是文件上的“文件资源”API，您只需要访问 EL 上下文。
我会考虑这个...这是一个暮光之城，像 PDF 这样的复杂文档很可能会使用服务来提供。那么为什么不是一个“简单”的文档，因为它不是 webapp 本身的控制流的一部分，而是一个松散相关过程中的技术工件。
我可以想象在基于字符的内容（HTML/CSS/JS/TXT/等）中需要 EL 上下文，但是 PDF？也许这有帮助：stackoverflow.com/q/9391838 和 stackoverflow.com/q/13015410

【解决方案2】：

我不太确定那里发生了什么，但我是这样做的...

保留您已有的 web.xml 文件。

像plain.xhtml这样创建xhtm文件...

<ui:composition
    xmlns:ui="http://java.sun.com/jsf/facelets">
    hi #{request.contextPath}/
</ui:composition>

现在转到 .../plain.txt

应该没问题

【讨论】：

这会产生错误的内容类型标头作为响应。 OP 明确想要text/plain。
你可以监听 preRenderView 事件，比如... 然后 FacesContext fc = FacesContext.getCurrentInstance(); ExternalContext ec = fc.getExternalContext(); Map 参数 = ec.getRequestParameterMap(); ec.setResponseContentType("text/plain"); ec.getResponseOutputWriter().write("一些文本内容"); //或从文件中读取... String y = ec.getRealPath(((HttpServletRequest) ec.getRequest()).getRequestUrl()); fc.responseComplete();但我想有很多工作