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POServing files with JSF 2 / CDI, using bookmarkable URLs
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  1. POServing files with JSF 2 / CDI, using bookmarkable URLs
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    copied!<p>My main question is : Is there a "good practice" to serve binary files (PDF, docs, etc) using JSF 2 with CDI, and using bookmarkable URLs ?</p> <p>I've read the <a href="http://download.oracle.com/otndocs/jcp/jsf-2_1-mrel2-eval-oth-JSpec/" rel="nofollow noreferrer">JSF 2 spec (JSR 314)</a> and I see it exists a "Resource Handling" paragraph. But it seems to be used only to serve static files put in the war or jar files. I didn't really understood if it exists a way to interact here by registering some specific ResourceHandler ...</p> <p>Actually, I was used to Seam's 2 way to do that : extending the <a href="http://docs.jboss.org/seam/2.2.0.GA/api/org/jboss/seam/web/AbstractResource.html" rel="nofollow noreferrer"><code>AbstractResource</code></a> class with <code>getResource(HttpServletRequest, HttpServletResponse)</code> method and <code>getResourcePath()</code> to declare which path to serve after <code>&lt;webapp&gt;/seam/resource/</code> URL prefix and declaring the <code>SeamResourceServlet</code> in the <code>web.xml</code> file.</p> <p>Here is what I did.</p> <p>I've first saw <a href="https://stackoverflow.com/questions/5498391/how-to-download-a-file-stored-in-a-database-with-jsf-2-0">How to download a file stored in a database with JSF 2.0</a> and tried to implement it.</p> <pre class="lang-html prettyprint-override"><code>&lt;f:view ... &lt;f:metadata&gt; &lt;f:viewParam name="key" value="#{containerAction.key}"/&gt; &lt;f:event listener="#{containerAction.preRenderView}" type="preRenderComponent" /&gt; &lt;/f:metadata&gt; ... &lt;rich:dataGrid columns="1" value="#{containerAction.container.files}" var="file"&gt; &lt;rich:panel&gt; &lt;h:panelGrid columns="2"&gt; &lt;h:outputText value="File Name:" /&gt; &lt;h:outputText value="#{file.name}" /&gt; &lt;/h:panelGrid&gt; &lt;h:form&gt; &lt;h:commandButton value="Download" action="#{containerAction.download(file.key)}" /&gt; &lt;/h:form&gt; &lt;/rich:panel&gt; &lt;/rich:dataGrid&gt; </code></pre> <p>And here is the beans :</p> <pre class="lang-java prettyprint-override"><code>@Named @SessionScoped public class ContainerAction { private Container container; /// Injections @Inject @DefaultServiceInstance private Instance&lt;ContainerService&gt; containerService; /// Control methods public void preRenderView(final ComponentSystemEvent event) { container = containerService.get().loadFromKey(key); } /// Action methods public void download(final String key) throws IOException { final FacesContext facesContext = FacesContext.getCurrentInstance(); HttpServletResponse response = (HttpServletResponse) facesContext.getExternalContext().getResponse(); final ContainerFile containerFile = containerService.get().loadFromKey(key); final InputStream containerFileStream = containerService.get().read(containerFile); response.setHeader("Content-Disposition", "attachment;filename=\""+containerFile.getName()+"\""); response.setContentType(containerFile.getContentType()); response.setContentLength((int) containerFile.getSize()); IOUtils.copy(containerFileStream, response.getOutputStream()); response.flushBuffer(); facesContext.responseComplete(); } /// Getters / setters public Container getContainer() { return container; } } </code></pre> <p>Here I had to <a href="http://seamframework.org/Community/Weld111AndTomcat7Problems" rel="nofollow noreferrer">switch to Tomcat 7</a> (I was using 6) in order to interpret correctly that EL expression. With <code>@SessionScoped</code> it worked, but not with <code>@RequestScoped</code> (when I clicked the button, nothing happend).</p> <p>But then I wanted to use a link instead of a button.</p> <p>I tried <code>&lt;h:commandLink value="Download" action="#{containerAction.download(file.key)}" /&gt;</code> but it generates some ugly javascript link (not bookmarkable).</p> <p>Reading the JSF 2 spec, it seems that there is a "Bookmarkability" feature, but it is not realy clear how to use it.</p> <p>Actually, it seems to work only with views, so I tried to create an empty view and created a <code>h:link</code> :</p> <pre class="lang-html prettyprint-override"><code>&lt;h:link outcome="download.xhtml" value="Download"&gt; &lt;f:param name="key" value="#{file.key}"/&gt; &lt;/h:link&gt; </code></pre> <pre class="lang-html prettyprint-override"><code>&lt;f:view ...&gt; &lt;f:metadata&gt; &lt;f:viewParam name="key" value="#{containerFileDownloadAction.key}"/&gt; &lt;f:event listener="#{containerFileDownloadAction.download}" type="preRenderComponent" /&gt; &lt;/f:metadata&gt; &lt;/f:view&gt; </code></pre> <pre class="lang-java prettyprint-override"><code>@Named @RequestScoped public class ContainerFileDownloadAction { private String key; @Inject @DefaultServiceInstance private Instance&lt;ContainerService&gt; containerService; public void download() throws IOException { final FacesContext facesContext = FacesContext.getCurrentInstance(); // same code as previously ... facesContext.responseComplete(); } /// getter / setter for key ... } </code></pre> <p>But then, I had a <code>java.lang.IllegalStateException: "getWriter()" has already been called for this response</code>.</p> <p>Logic as when a view initiates, it uses getWritter to initialize the response.</p> <p>So I created a Servlet which does the work and created the following <code>h:outputLink</code> :</p> <pre class="lang-html prettyprint-override"><code>&lt;h:outputLink value="#{facesContext.externalContext.request.contextPath}/download/"&gt; &lt;h:outputText value="Download"/&gt; &lt;f:param name="key" value="#{file.key}"/&gt; &lt;/h:outputLink&gt; </code></pre> <p>But even if that last technique gives me a bookmarkable URL for my file, it is not really "JFS 2" ...</p> <p>Do you have some advice ?</p>
 

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