7 Replies Latest reply on Aug 20, 2007 8:11 PM by alexg79

Ajax4JSF mediaOutput tag and Seam

alexg79 Aug 20, 2007 6:10 PM

I'm trying to display thumbnails of images I have on the database using a4j:mediaoutput, like this:

<a4j:mediaOutput element="img" mimeType="image/jpeg" createContent="#{download.sendThumbnail}" value="#{screenshot.id}" />

The "download" component looks like this:

@Name("download")
@Stateless
public class DownloadBean implements Download {

 @PersistenceContext
 private EntityManager em;

 @Override
 public void sendImage(OutputStream os, Object screenshotId) throws IOException {
 Screenshot ss = em.find(Screenshot.class, screenshotId);
 if (ss != null)
 os.write(ss.getImageData());
 }

 @Override
 public void sendThumbnail(OutputStream os, Object screenshotId) throws IOException {
 Screenshot ss = em.find(Screenshot.class, screenshotId);
 if (ss != null)
 os.write(ss.getThumbnailData());
 }

}

When loading the page, however, I get the following exception in the server console:

00:49:02,174 ERROR [[default]] Servlet.service() for servlet default threw exception
javax.faces.el.EvaluationException: /entry.xhtml @170,79 createContent="#{download.sendThumbnail}": Target Unreachable, identifier 'download' resolved to null
 at com.sun.facelets.el.LegacyMethodBinding.invoke(LegacyMethodBinding.java:73)
 at org.ajax4jsf.framework.resource.UserResource.send(UserResource.java:110)
 at org.ajax4jsf.framework.resource.ResourceLifecycle.send(ResourceLifecycle.java:86)
 at org.ajax4jsf.framework.resource.InternetResourceService.sendResource(InternetResourceService.java:256)
 at org.ajax4jsf.framework.resource.InternetResourceService.serviceResource(InternetResourceService.java:240)
 at org.ajax4jsf.framework.resource.InternetResourceService.serviceResource(InternetResourceService.java:141)
 at org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:261)
 at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:60)
 at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:68)
 at org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:58)
 at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:68)
 at org.jboss.seam.debug.hot.HotDeployFilter.doFilter(HotDeployFilter.java:68)
 at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:68)
 at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:149)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
 at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
 at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:580)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
 at java.lang.Thread.run(Thread.java:619)

So how can it possibly be null? The "download" component is loaded ok, since it shows up in the Seam component list during deploy.
What am I doing wrong? Could this be a configuration problem?
Using JBoss 4.2.1GA, Seam CVS and Ajax4JSF v1.1.1.

1. Re: Ajax4JSF mediaOutput tag and Seam

pmuir Aug 20, 2007 6:27 PM (in response to alexg79)

IIRC correctly there is some incompatibility between the mediaOutput and Seam, I discussed it with Alex Smirnov once, but I can't remember the outcome. Post this on the richfaces dev forum/check for a JIRA issue in the RF/A4J jiras.
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2. Re: Ajax4JSF mediaOutput tag and Seam

alexg79 Aug 20, 2007 6:45 PM (in response to alexg79)

Hm, you are probably referring to this: http://jira.jboss.org/jira/browse/AJSF-54.
Forum link: http://www.jboss.com/index.html?module=bb&op=viewtopic&t=107203
I gather the only workaround for now is to define "download" as a managed bean in faces-config.xml? This should work for me since I don't (at the moment) use any Seam components from this one.
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3. Re: Ajax4JSF mediaOutput tag and Seam

alexg79 Aug 20, 2007 7:15 PM (in response to alexg79)

Tried to use a managed bean but hit a snag...where to get a reference to the persistence context? If this was JEE5, all I had to do was to have the container inject it to my managed bean, but since it's not, I have nothing.
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4. Re: Ajax4JSF mediaOutput tag and Seam

matt.drees Aug 20, 2007 7:25 PM (in response to alexg79)
Assuming you're using a seam-managed persistence context, you can just do
EntityManager entityManager = (EntityManager) Component.getInstance("entityManager");
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5. Re: Ajax4JSF mediaOutput tag and Seam

alexg79 Aug 20, 2007 7:27 PM (in response to alexg79)

1. I'm not using a seam-managed persistence context
2. Component.getInstance() would just throw an exception saying that there is no application context active
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6. Re: Ajax4JSF mediaOutput tag and Seam

alexg79 Aug 20, 2007 7:50 PM (in response to alexg79)

Ok, "kinda" solved this with the ugliest imaginable solution:
Binding the entity manager factory to JNDI and then looking it up in said managed bean.
Please, offer me a plausible alternative :(
This solution works, but introduces a vendor dependency (the JNDI structure being different for each vendor).
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7. Re: Ajax4JSF mediaOutput tag and Seam

alexg79 Aug 20, 2007 8:11 PM (in response to alexg79)

All in all, using servlets instead of a4j:mediaOutput is starting to look like a better solution -- I get to control what kind of URLs I use (those generated by a4j:mediaOutput are among the ugliest ever) and what the headers look like.
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