org.apache.jasper.JasperException: /WEB-INF/jsp/home.jsp(45,0) Unknown attribute type (java.util.List<net.bigbark.item.Item>) for attribute items.

The thing that was driving me crazy about this was that it ran just fine in a local Jetty container (started with “mvn jetty:run“).   The problem was this line in src/main/webapp/WEB-INF/tags/ui/article-list.tag:

<%@ attribute name="items" required="true" type="java.util.List<net.bigbark.item.Item>" %>

Apparently Jetty’s JSP implementation (which IIRC comes from Glassfish) allows one to use generic types, while the one in Tomcat (Jasper) does not.  Between the J2EE 1.4 tutorial documentation [1][2], the JSP 2.0 syntax reference [3], and the JSR-241 (JSP 2.1) final release specification [4], the only restriction I saw on the type attribute is that it must not reference a primitive type.  Does this mean that Jasper’s inability to handle a parameterized type reference is a bug?  It would appear that some Glassfish developer(s) allowed for this usage, which makes me wonder whether the corresponding Jasper developer(s) intentionally left out such support or simply never considered the possibility.

I changed the type attribute’s value to “java.util.List” (removed the generic type parameter), and the exception disappeared. C’est la vie!

-Bill
P.S. Here is the full stack trace; maybe the search engines will pick up on it and it will help someone else in the future — but probably not.

Jan 27, 2009 2:23:22 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet default threw exception
org.apache.jasper.JasperException: /WEB-INF/jsp/home.jsp(43,8) Unknown attribute type (java.util.List<net.bigbark.item.Item>) for attribute items.
at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40)
at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407)
at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:236)
at org.apache.jasper.compiler.Validator$ValidateVisitor.checkXmlAttributes(Validator.java:1164)
at org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:821)
at org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1512)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2343)
at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2393)
at org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2399)
at org.apache.jasper.compiler.Node$Root.accept(Node.java:489)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2343)
at org.apache.jasper.compiler.Validator.validate(Validator.java:1739)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:166)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:315)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:295)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:282)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:586)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:119)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:55)
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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302)
at net.sourceforge.stripes.action.ForwardResolution.execute(ForwardResolution.java:110)
at net.sourceforge.stripes.controller.DispatcherHelper$7.intercept(DispatcherHelper.java:483)
at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:158)
at net.bigbark.stripes.util.ResourceBundleInterceptor.intercept(ResourceBundleInterceptor.java:21)
at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155)
at net.sourceforge.stripes.controller.HttpCacheInterceptor.intercept(HttpCacheInterceptor.java:99)
at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155)
at net.sourceforge.stripes.controller.BeforeAfterMethodInterceptor.intercept(BeforeAfterMethodInterceptor.java:113)
at net.sourceforge.stripes.controller.ExecutionContext.proceed(ExecutionContext.java:155)
at net.sourceforge.stripes.controller.ExecutionContext.wrap(ExecutionContext.java:74)
at net.sourceforge.stripes.controller.DispatcherHelper.executeResolution(DispatcherHelper.java:477)
at net.sourceforge.stripes.controller.DispatcherServlet.executeResolution(DispatcherServlet.java:293)
at net.sourceforge.stripes.controller.DispatcherServlet.doPost(DispatcherServlet.java:177)
at net.sourceforge.stripes.controller.DispatcherServlet.doGet(DispatcherServlet.java:67)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at net.sourceforge.stripes.controller.DynamicMappingFilter$2.doFilter(DynamicMappingFilter.java:363)
at net.sourceforge.stripes.controller.StripesFilter.doFilter(StripesFilter.java:246)
at net.sourceforge.stripes.controller.DynamicMappingFilter.doFilter(DynamicMappingFilter.java:350)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.wideplay.warp.hibernate.SessionPerRequestFilter.doFilter(SessionPerRequestFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:46)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:568)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:283)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:767)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:697)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:889)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
at java.lang.Thread.run(Thread.java:619)

Each system had just one problem: the iMac had no sound, and the MBP was missing a lot of UI eye candy.  A quick look at the Apple discussion forums revealed that the iMac just needed an updated audio driver, so I downloaded the latest Realtek HD audio driver for Vista (direct link: R2.14) and everything was gravy.

The MBP problem took a bit longer to resolve, mostly because I didn’t dedicate any real time to tracking it down until January 15th.    I asked uncle Google and discovered that the Windows installer weighs your system’s ability to handle the higher-end Aero features, and if its soul is found lacking, you are relegated to the weeping and gnashing of teeth that is Aero Basic.  Apparently with the default drivers, my system did not pass the test.  How sad!  :’(

The fix turned out to be rather simple, once you know where to look.  Here is one of the blogs that helped.  It turns out I didn’t even need most of the information there; all I really needed was to tell Windows to calculate the “Windows Experience Index” score, and voila, Glass/Peek/etc. were instantly enabled.

P.S.  If the timing of this post seems odd, it’s because I wrote it on January 15th and forgot to publish until January 27th. 

This time, however, I have a reason I’m just doing it so I have a way to organize some thoughts that are too long for microblogging. Call it “macromicroblogging”, if you will, but do not confuse it with plain old “blogging”.

For the record, I expect to mostly be expounding on my tweets, and talking about ORBlogs [1] [2] and other local tech stuff.

@tomturnbull said, in this Flickr post:

Reduced “following” by 124. It’s still too many to be useful. Has Twitter become noise?

I started typing away in the comment box, then realized that it is extremely unlikely that anyone would ever read it, other than perhaps Tom (if he even monitors his Flickr comments; many don’t) and perhaps a random few who view his post in the future.  There have been quite a few such instances lately when a tweet or comment on someone else’s blog just didn’t feel right, because whatever I said would get washed away in the stream, and I wanted something I could easily reference later.  Basically, I’m lazy and like to repeat myself as little as possible.

So to make my comment useful (to me) in the future, I would have to save the URL to his post and hope that neither it nor my comment are never deleted, marked private, moved, or otherwise lost in the sands of time.  Then of course to have someone read it, I would have to dig up that URL again and send it to them, and because most people are used to a certain flow of Flickr usage, I would probably tell them specifically to read the post, then scroll down and read my comment.  Blech.

Now, most of the people I know who I imagine will read this post are seasoned bloggers, and you guys are probably thinking to yourselves at this moment “Duh!  That’s why you have your own blog!”  To you, I say: please bear with me, I have become very jaded about blogging (my own, not others’), and part of the reason for this post is justifying to myself why I’m facing down this beast again.

I have been so resistant to blogging that when I first started running into the above-described problem regularly, the first solution I considered was to go ahead and use others’ sites, then try to use my profile on one or more of the aggregators I have experimented with (Strands, FriendFeed, chi.mp, etc.) to gather all my content back into one place. There are problems with this approach, though: the continued existence of my content is still at someone else’s whim, and these tools cannot currently, pick up everything and still be useful in any practical way. For example, if I leave a comment on someone else’s blog, but want it to show up on my FriendFeed, I would need a way to get that comment into the aggregator; I could create a Yahoo! Pipe that gets the comment feed for their article (or entire blog, depending on what they have available and whether I expect to ever post there again) and filters out all comments but mine. Then I would add that pipe as a new feed to my aggregator… and you can see how this would get rather unwieldy pretty quickly. Sure, I could have one pipe pull lots of comment feeds and do its filtering, but that just shifts the ever-growing bulk to another place.  Pretty soon, you’re doing multiple pipes each pulling multiple sources, or who knows what else that would be even worse. Oh, and did I mention that by this method, you lose the context of whatever you were responding to in the first place?  And how do you separate the high-volume and low-volume data sources, so your comments on others’ sites are not drowned out by your Twitter addiction?  Obviously, this was not a solution I wanted to waste a lot of effort on.

However, I was still not convinced that my frustration was reason enough to start another blog.  So I thought up another solution: use others’ sites as before, but create a mechanism (e.g. web application, browser plugin, or standalone program) which would capture my content, along with its context (e.g. the Flickr post I was replying to), and store it on a site I control with a simple permanent address.  I realize that what I’m describing sounds almost like it could be accomplished by just taking screenshots and posting them on a blog, but I would also want such a mechanism to replicate the original machine-friendly (i.e. full-text searchable) content, not take pictures of it; store HTML like Iterasi, but snippets rather than whole pages; auto-update when the original source changes (i.e. more comments on the same thread) like Calagator, but with wiki- or Subversion-like revision history (in case of unwanted modification, deletion, errors, or site restructuring/closure).  And of course easy separation from higher-volume feeds of other types (e.g. tweetstreams, photostreams).  Since this solution is custom-tailored to my requirements, I only have one problem with it, but that problem is a doozy:  I would have to actually build the damn thing. 

So, I have finally given up the ghost, and decided that I will go ahead and blog to scratch the itch, and just use pingbacks where possible, or use a comment box to leave a link to my reply (with enough explanation that people hopefully realize it’s not spam).  At least, that’s what I will do for now.  In a month I’ll have probably moved on to something else, making this whole exercise and the time I have spent writing this useless except as temporary catharsis.

Alright, now that I have written about as much as I think I can stand, I will close with the comment I was going to leave on Tom’s screenshot.

Like other forms of online communication, Twitter seems to go through periods in which increases in usage volume far outpace the evolution of the sophistication of its users and the tools they use to interact with it. In other words: people find a new toy and start playing with it, some in ways unanticipated by the creators, by which a new need arises, then someone comes up with a way to fill that need. More sophisticated tools will appear to deal with the current problems that some people have with social media; for me, Tweetdeck and Twhirl are both excellent Twitter clients and fine examples of this.  Each has a unique strength that solves a problem I encountered as my Twitter usage grew and evolved, and allowed me to continue doing so in ways that were not practical without them.  For the record, I use Tweetdeck for its grouping feature, and Twhirl for its simple multiple-account management (and FriendFeed integration).  Anyone who has used either knows exactly what I mean. And just this morning, Justin Kistner brought up (in a tweet, naturally) a Twitter client idea that caught my attention and sparked my imagination.  I might have to do something about it.

The cycle will continue, of course; new usage will lead to new problems, to new solutions, ad infinitum — or until the next shiny new toy distracts them all to the point of not caring anymore.  However, I think it’s possible that Twitter will last quite a while before that happens, if it happens.  Twitter is, at its heart, simply a high-speed, high-capacity message bus, with some excellent additional features built in (simple public API facilitating rich client proliferation, 2-way SMS interface, arguably well-designed web interface user experience) that really give it an edge over similar services.  And don’t overlook the value of forced brevity; I’m sure we have all seen people evade the spirit of the 140-character limit by splitting across far too many tweets, and thought to ourselves “how ugly!” 

Cheers,
-Bill (@wajiii)

Cheers,
-Bill (@wajiii)

P.S. Speaking of shiny toys, why did I create a new blog rather than writing this on my posterous or the Crafty Wook blog that @Gaarbacca and I share? Simple. First, I like each of those sites for what they are — my time-based moblog and our Wookiee-/SWG-related blog, respectively — and I don’t want to dilute the focus of either, or change either visual style to befit my more verbose, less time-oriented content like this. Second, I really like WordPress and I wanted a chance to do a lot more playing around with it, without breaking the Crafty Wook blog. Okay?