Raible Designs

Versioning Static Assets with UrlRewriteFilter

A few weeks ago, a co-worker sent me interesting email after talking with the Zoompf CEO at JSConf.

One interesting tip mentioned was how we querystring the version on our scripts and css. Apparently this doesn't always cache the way we expected it would (some proxies will never cache an asset if it has a querystring). The recommendation is to rev the filename itself.

This article explains how we implemented a "cache busting" system in our application with Maven and the UrlRewriteFilter. We originally used querystring in our implementation, but switched to filenames after reading Souders' recommendation. That part was figured out by my esteemed colleague Noah Paci.

Our Requirements

• Make the URL include a version number for each static asset URL (JS, CSS and SWF) that serves to expire a client's cache of the asset.
• Insert the version number into the application so the version number can be included in the URL.
• Use a random version number when in development mode (based on running without a packaged war) so that developers will not need to clear their browser cache when making changes to static resources. The random version number should match the production version number formats which is currently: x.y-SNAPSHOT-revisionNumber
• When running in production, the version number/cachebust is computed once (when a Filter is initialized). In development, a new cachebust is computed on each request.

In our app, we're using Maven, Spring and JSP, but the latter two don't really matter for the purposes of this discussion.

Implementation Steps
1. First we added the buildnumber-maven-plugin to our project's pom.xml so the build number is calculated from SVN.

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>buildnumber-maven-plugin</artifactId>
    <version>1.0-beta-4</version>
    <executions>
        <execution>
            <phase>validate</phase>
            <goals>
                <goal>create</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <doCheck>false</doCheck>
        <doUpdate>false</doUpdate>
        <providerImplementations>
            <svn>javasvn</svn>
        </providerImplementations>
    </configuration>
</plugin>

2. Next we used the maven-war-plugin to add these values to our WAR's MANIFEST.MF file.

<plugin>
    <artifactId>maven-war-plugin</artifactId>
    <version>2.0.2</version>
    <configuration>
        <archive>
            <manifest>
                <addDefaultImplementationEntries>true</addDefaultImplementationEntries>
            </manifest>
            <manifestEntries>
                <Implementation-Version>${project.version}</Implementation-Version>
                <Implementation-Build>${buildNumber}</Implementation-Build>
                <Implementation-Timestamp>${timestamp}</Implementation-Timestamp>
            </manifestEntries>
        </archive>
    </configuration>
</plugin>

3. Then we configured a Filter to read the values from this file on startup. If this file doesn't exist, a default version number of "1.0-SNAPSHOT-{random}" is used. Otherwise, the version is calculated as ${project.version}-${buildNumber}.

private String buildNumber = null;

...
@Override
public void initFilterBean() throws ServletException {
    try {
        InputStream is = 
            servletContext.getResourceAsStream("/META-INF/MANIFEST.MF");
        if (is == null) {
            log.warn("META-INF/MANIFEST.MF not found.");
        } else {
            Manifest mf = new Manifest();
            mf.read(is);
            Attributes atts = mf.getMainAttributes();
            buildNumber = atts.getValue("Implementation-Version") + "-" + atts.getValue("Implementation-Build");
            log.info("Application version set to: " + buildNumber);
        }
     } catch (IOException e) {
        log.error("I/O Exception reading manifest: " + e.getMessage());
     }
}

...

    // If there was a build number defined in the war, then use it for
    // the cache buster. Otherwise, assume we are in development mode 
    // and use a random cache buster so developers don't have to clear 
    // their browswer cache.
    requestVars.put("cachebust", buildNumber != null ? buildNumber : "1.0-SNAPSHOT-" + new Random().nextInt(100000));

4. We then used the "cachebust" variable and appended it to static asset URLs as indicated below.

<c:set var="version" scope="request" 
    value="${requestScope.requestConfig.cachebust}"/>
<c:set var="base" scope="request"
    value="${pageContext.request.contextPath}"/>

<link rel="stylesheet" type="text/css" 
    href="${base}/v/${version}/assets/css/style.css" media="all"/>

<script type="text/javascript" 
    src="${base}/v/${version}/compressed/jq.js"></script>

The injection of /v/[CACHEBUSTINGSTRING]/(assets|compressed) eventually has to map back to the actual asset (that does not include the two first elements of the URI). The application must remove these two elements to map back to the actual asset. To do this, we use the UrlRewriteFilter. The UrlRewriteFilter is used (instead of Apache's mod_rewrite) so when developers run locally (using mvn jetty:run) they don't have to configure Apache.

5. In our application, "/compressed/" is mapped to wro4j's WroFilter. In order to get UrlRewriteFilter and WroFilter to work with this setup, the WroFilter has to accept FORWARD and REQUEST dispatchers.

<filter-mapping>
    <filter-name>rewriteFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<filter-mapping>
    <filter-name>WebResourceOptimizer</filter-name>
    <url-pattern>/compressed/*</url-pattern>
    <dispatcher>FORWARD</dispatcher>
    <dispatcher>REQUEST</dispatcher>
</filter-mapping>

Once this was configured, we added the following rules to our urlrewrite.xml to allow rewriting of any assets or compressed resource request back to its "correct" URL.

<rule match-type="regex">
    <from>^/v/[0-9A-Za-z_.\-]+/assets/(.*)$</from>
    <to>/assets/$1</to>
</rule>
<rule match-type="regex">
    <from>^/v/[0-9A-Za-z_.\-]+/compressed/(.*)$</from>
    <to>/compressed/$1</to>
</rule>
<rule>
    <from>/compressed/**</from>
    <to>/compressed/$1</to>
</rule>

Of course, you can also do this in Apache. This is what it might look like in your vhost.d file:

RewriteEngine    on
RewriteLogLevel  0!
RewriteLog       /srv/log/apache22/app_rewrite_log
RewriteRule      ^/v/[.A-Za-z0-9_-]+/assets/(.*) /assets/$1 [PT]
RewriteRule      ^/v/[.A-Za-z0-9_-]+/compressed/(.*) /compressed/$1 [PT]

Whether it's a good idea to implement this in Apache or using the UrlRewriteFilter is up for debate. If we're able to do this with the UrlRewriteFilter, the benefit of doing this at all in Apache is questionable, especially since it creates a duplicate of code.

What's New in Maven 3.0 with Matthew McCullough

Last night, I attended the Denver JUG meeting to hear some excellent talks by Matthew McCullough and Tim Berglund. I took notes during Matthew's talk, but my battery ran out before Tim's talk started. Below are my notes.

Matthew started out by described the differences between Maven 2 and Maven 3. As he began, he emphasized it wasn't a beginner talk, but mostly for existing Maven users that understand how to read a pom.xml and such.

The Roadmap
Commits to Maven 3 have been happening for the last 3 years. Matthew is not an employee of Sonatype, but he mentioned their name quite a bit in his talk. Sonatype has hired several committers (7 that Matthew knows of by name) that now work on Maven 3 full-time. For compatibility with Maven 2, the project has 450 integration tests and they test it against 100s of Maven 2 projects. Maven 3 has plugin classloader partitioning and a legacy simulation layer for old plugins.

The main improvement in Maven 3 is speed. It's been performance tuned to be 50% to 400% faster. Benchmarks (guaranteed by integration tests) include better: Disk I/O, Network I/O, CPU and Memory. Another new feature is extensibility so Maven is a better library rather than just a command-line tool. Now there's a library and APIs that you can use to do the things that Maven does. Plexus has been replaced with Guice and it's now much easier to embed Maven (Polyglot Maven and Maven Shell are examples of this).

Below are a number of other changes between Maven 2 and Maven 3.

• Syntax: pom.xml still uses <modelVersion>4.0.0</modelVersion> so it can be a drop-in replacement for Maven 2 projects.
• Validations: poms are heavily validated against common mistakes, warns when plugin versions are not specified (use mvn validate to see issues), blocks duplicate dependencies (examined in same POM only, conflict resolution used otherwise).
• Help URLs: wiki page URLs now shown for all error messages. One of the first Apache projects to do this.
• Removals: profiles.xml external file support removed, Maven 1.0 repository support removed <layout>legacy</layout> (it's been 5 years since any commits to Maven 1).
• Behavior: SNAPSHOTs always deployed with date-stamps, artifact resolution caching has been improved to do less checking (override with mvn <phase> -U).
• Plugins: version auto-selection favors RELEASEs over SNAPSHOTs (opposite for Maven 2), versions cannot be specified as RELEASE or LATEST, plugins only resolved from <pluginRepository> locations.
• See the Plugin Compatibility Matrix to see if your favorite plugins are compatible.

Maven 3 hopes to be a drop-in replacement for Maven 2, but non backwards-compatible changes will be happening in Maven 3.1. It's anticipated release is Q1 of 2011 and will likely contain the following features.

• "Mixins" for direct dependencies
• Site plugin takes over <reporting>
• Backwards compatibility by <modelVersion
• There's a good chance 3.1 breaks compatibility with legacy POMs

Another new thing in Maven 3 is Toolchain. Toolchain a common way to configure your JDK for multiple plugins. There are only a handful of plugins that are toolchain-enabled. User tool chain definitions are defined in ~/.m2/toolchains.xml. To use different toolchains (JDKs), you specify a vendor and version as part of your plugin configuration.

Maven Shell is a high performance console that's a Maven 3 add-on. It's hosted at GitHub to make community contributions easier. It goes on your command line and it offers syntax highlighting and context-sensitive help (by typing ? at the command prompt).

Another major improvement in Maven 3 is Polyglot Maven. Tools like Gant and Buildr have made Maven look ancient, but they've also given it a good challenge. Maven 3 is likely to leapfrog these tools because of its ability to use different languages for your build configuration. Currently, 6 languages are supported. Polyglot Maven is a super-set distribution of Maven 3. It's not shipped with Maven 3 core because it contains all the other language implementations and is quite large. Polyglot Maven also contains a translate tool that allows you to convert any-to-any language. It has a DSL framework with Macros and Lifecycle Hooks. Macros allows for more concise syntax.

After talking about Polyglot Maven a bit, Matthew shows us a demo translating pom.xml to pom.yaml and then running the build. After that, he showed us examples of what a pom looks like when defined in Clojure, Scala and Groovy. Someone asked about file parsing performance and Matthew said different languages would cause a single-digit performance difference as part of your build process. Personally, I can't help but think any non-XML parser would be faster than the XML parser.

In regards to m2eclipse, a new drop (0.10) occurred a few weeks ago and it's one of the highest quality releases to date. It has major refactoring and many performance improvements.

For sample Maven projects see Matthew's Maven Samples.

I very much enjoyed Matthew's talk, both because of his presentation techniques and because he had a lot of good information. While I've tried Maven 3 and Shell in the past, I've been newly inspired to start using them again on a daily basis.

Tim's talk on Decision Making was also excellent. The biggest things I learned were that conflict is good (idea-wise, not personal) and things to look out for between teams (fault lines). Hopefully both Tim and Matthew post their slides so I can link to them here.

My TSSJS 2010 Presentations and Summary

This afternoon, I delivered my last talk at TSSJS 2010 on The Future of Web Frameworks. It's true that I made some bold statements, but please remember that this is my personal opinion, based on my experience. For the most part, I've been involved in super high-traffic websites for the last few years and this has influenced my opinion on web frameworks. Just because I don't recommend your favorite framework doesn't mean it won't work for you. In fact, many of the best web applications today were built without an open source (or commercial) web framework. In the end, it's not as much about the web framework you're using as it is about hiring smart people. Below is my slide deck from this talk.

Yesterday, I did a GWT vs. Flex Smackdown with James Ward. While there wasn't as much trash talking as I'd hoped, I enjoyed delivering it and disputing the greatness of Flex. Below is the presentation that James and I delivered.

The show itself was great this year. It had more attendees than I've seen in a long time. There were a lot of really interesting sessions and and an often humorous Twitter back-channel. I attended quite a few talks and jotted down my notes from several of them. Please see the links below if you're interested in the sessions I attended. You can view all of the presentations from TSSJS 2010 on SlideShare.

• What's Happening in the Java World?
• Software Quality: The Quest for the Holy Grail?
• The Cloud Computing Continuum with Bob McWhirter
• Highly Interactive Software with Java and Flex
• C++, Java and .NET: Lessons Learned from the Internet Age
• Developing Rich Web Service APIs with Java
• What's New in Spring 3.0

Thanks to everyone who came to Vegas and to TheServerSide for an excellent conference.

What's New in Spring 3.0

This morning, I attended Rod Johnson's What's New in Spring 3.0 keynote at TSSJS. Rod ditched his slides for the talk and mentioned that this might be risky. Especially since he was pretty jetlagged (flew in from Paris at 11pm last night). Below are my notes from his talk.

The most important thing for the future of Java is productivity and cloud computing. The focus at SpringSource is heavily on productivity and not just on improving the Spring codebase. If you look at the comparisons out there between Rails and Spring, it's not an apples-to-apples comparison. The philosophy with Spring has always been the developer is always right. However, if you look at something like Rails, you'll see it's far more prescriptive. That layer of opinionated frameworks is important in that it improves your productivity greatly.

SpringSource is putting a lot of emphasis on improving developer productivity with two opinionated frameworks: Grails and Spring Roo. To show how productive developers can be, Rod started to build a web app with Spring Roo. As part of this demo, he mentioned we'd see many of the new features of Spring 3: RestTemplate, @Value and Spring EL.

Rod used STS to write the application and built a Twitter client. After creating a new project using File -> New Roo Project, a Roo Shell tab shows up at the bottom. Typing "hint" tells you what you should do write away. The initial message is "Roo requires the installation of a JPA provider and associated database." The initial command is "persistence setup --provider HIBERNATE --database HYPERSONIC_IN_MEMORY". After running this, a bunch of log messages are shown on the console, most of them indicating that pom.xml has been modified.

The first file that Rod shows is src/main/resources/META-INF/spring/applicationContext.xml. It's the only XML file you'll need in your application and includes a PropertyPlaceHolderConfigurer, a context:component-scan for finding annotations and a transaction manager.

After typing "hint" again, Roo indicates that Rod should create entities. He does this by running "ent --class ~.domain.Term --testAutomatically". A Term class (with a bunch of annotations) is created, as well as a number of *.aj files and an integration test. Most of the files don't have anything in them but annotations. The integration test uses @RooIntegrationTest(entity=Term.class) on its class to fire up a Spring container in the test and do dependency injection (if necessary). From there, Rod demonstrated that he could easily modify the test to verify the database existed.

private SimpleJdbcTemplate jt;

@Autowired
public void init(DataSource ds) {
    this.jt = new SimpleJdbcTemplate(ds);
}

@Test 
public void testDb() {
    jt.queryForInt("SELECT COUNT(0) FROM TERM");
}

Interestingly, after running the test, you could see a whole bunch of tests being run, not just the one that was in the class itself. From there, he modified the Term class to add two new properties: name and searchTerms. He also used JSR 303's @NotNull annotation to make the fields required.

@Entity
@RooJavaBean
@RooToString
@RooEntity
public class Term {

    @NotNull
    private String name;

    @NotNull
    private String searchTerms;
}

Next, Rod added a new test and showed that the setters for these properties were automatically created and he never had to write getters and setters. This is done by aspects that are generated beside your Java files. Roo is smart enough that if you write toString() methods in your Java code, it will delete the aspect that normally generates the toString() method.

To add fields to an entity from the command lie, you can run commands like "field string --fieldName text --notNull" and "field number --type java.lang.Long --fieldName twitterId --notNull". The Roo Shell is also capable of establishing relationships between entities.

After successfully modifying his Entities, Rod started creating code to talk to Twitter's API. He used RestTemplate to do this and spent a good 5 minutes trying to get Eclipse to import the class properly. The best part of this demo was watching him do what most developers do: searching Google for RestTemplate to get the package name to import.

After awkward silence and some fumbling, he opened an existing project (that had the dependencies properly configured) and used Java Config to configure beans for the project. This was done with a @Configuration annotation on the class, @Value annotations on properties (that read from a properties file) and @Bean annotations for the beans to expose. The first time Rod tried to run the test it failed because a twitter.properties file didn't exist. After creating it, he successfully ran the test and successfully searched Twitter's API.

The nice thing about @Configuration is the classes are automatically picked up and you don't need to configure any XML to recognize them. Also, in your Java classes, you don't have to use @Autowired to get @Bean references injected.

After this, Rod attempted to show a web interface of the application. He started the built-in SpringSource tc Server and proceeded to show us Tomcat's 404 page. Unfortunately, Tomcat seemed to startup OK (no errors in the logs), but obviously something didn't work well. For the next few silent moments, we watched him try to delete web.xml from Eclipse. Unfortunately, this didn't work and we weren't able to see the scaffolding the entities that Rod created.

At this point, Rod opened a completed version of the app and was able to show it to us in a browser. You could hear the murmur of the crowd as everyone realized he was about to show the the Twitter search results for #tssjs. Most of the tweets displayed were from folks commenting about how some things didn't work in the demo.

In summary, there's some really cool things in Spring 3: @Configuration, @Value, task scheduling with @Scheduled and one-way methods with @Async.

Final points of SpringSource and VMWare: they're committed to Java and middleware. Their big focus is providing an integrated experience from productivity to cloud. There's other languages that are further along than Java and SpringSource is trying to fix that. One thing they're working on is a private Java cloud that companies can use and leverage as a VMWare appliance.

I think there's a lot of great things in Spring 3 and most users of Roo seem to be happy with it. It's unfortunate that the Demo Gods frowned upon Rod, but it was cool to see him do the "no presentation" approach.

Developing Rich Web Service APIs with Java

This afternoon, I attended Ryan Heaton's talk on Developing Rich Web Service APIs with Java. I've always admired Ryan's work and what he's done with Enunciate. Below are my notes from his talk.

We've come a long way from the WS (SOAP) <-> EJB days. There are many tools that you can use to develop web services today. A Web Service is an API that's accessible over a network via platform-independent protocol. Historical examples of web services (in chronological order):

• CORBA
• DCOM
• RMI
• SOAP
• REST

A Web Service is composed of code wrapped with a container and it's bound to a contract. The table below shows the types of web services and their equivalent Java standard.

JAXB is the standard technology used to marshal XML <-> Java. It's annotation-driven, using @XmlRootElement, @XmlElement and @XmlAttribute to translate Java properties to XML.

JAX-WS is a Java standard, outputs classes as SOAP endpoints and it's annotation-driven. @WebService and @WebMethod are the main annotations. @WebMethod is only needed if you're trying to expose a non-public method.

JAX-RS is a Java standard used to expose REST services. Not surprisingly, it's annotation-driven. The class itself needs to be annotated with @Path. Methods are annotated with @GET, @PUT, @POST or @DELETE. If you need to pass in a parameter to a method, you can add a path parameter like the following:

@Path("/{id}")
@GET
public Person readPerson(@PathParam("id") String id);

To specify the possible mime-type outputs of a method, you can use the @Produces annotation. For example:

@Produces({"application/xml", "application/json"})

You can also do this for input methods with the @Consumes annotation.

For JSON, there's no Java standard. However, there's a number of libraries available, including Jackson, Jettison, GSON, XStream. Personally, I've used Jackson and highly recommend it.

The major players in exposing Java code as JAX-WS and JAX-RS services are Oracle, Spring and JBoss. Oracle (formerly Sun) has implemented the JAX-WS reference implementation and it's called Metro (a.k.a. JAX-WS RI). For JAX-RS, Oracle has the Jersey project. For Spring, the JAX-WS and JAX-RS implementation is Apache CXF. JBoss has JBoss-WS and RESTEasy.

There's also a number of custom containers for exposing web services. For example, AMF (implementations: BlazeDS, GraniteDS), GWT-RPC (GWT), JSON-PRC (DWR), Atom (Abdera), OpenSocial (Shindig).

The contract is a very important part of a web service API. It's composed of an Interface Definition Language (WSDL, WADL JSON Schema), Developer Docs (text, context, preconditions, restrictions), example code and client libraries.

Enunciate allows you to create your contract for your web services. It's a build-time WS Development tool. It generates developer documentation and client-side libraries (for Java, C/C++, Objective C, ActionScript and Ruby). It leverages existing specs (JAX-*) and fails fast at compile time.

From there, Ryan gave us a demo of Enunciate and how it could easily create an API website based on JAX-RS annotations.

I liked Ryan's talk and I'm definitely a fan of Enunciate. While I didn't learn anything new, I think there's a lot of Java developers that don't know about the various standards and how easy it is to develop web services. Hopefully by taking notes from Ryan's talk, I'll get the word out a bit more and make more folks aware of Enunciate. On a related note, Sonatype has a good post on how they documented the Nexus API with Enunciate.

C++, Java and .NET: Lessons Learned from the Internet Age

Today at TSSJS, I attended Cameron Purdy's keynote titled C++, Java and .NET: Lessons learned from the Internet Age, and What it means for the Cloud and Emerging Languages.

His talk was a retrospective of the trade-offs compared to C++ illustrated by Java, C# and other VM-based programming languages with Garbage-Collection, scripting languages simultaneously thrived, and what this teaches us about the applicability of technology to emerging challenges and environments such as cloud computing. Why did Java become so successful? Some folks say it was marketed better, but it was Sun - so we know that could've have been possible.

Cameron is the VP of Development for Oracle Fusion Middleware, responsible for the Coherence Data Grid product which has Java, C# and C++ versions. Data Grids are RAID for servers. It provides a reliable data tier with a single, consistent view of data and enabled dynamic data capacity including fault tolerance and load balancing. The servers cooperate together and act as an organism to manage their information.

Java when it first came out very much looked like evolution. From a C++ programmers perspective, Java was bloated.

Below are Cameron's Top 10 Reasons Why Java has been able to supplant C++. This started happening around 1996-97. Warning to Language Fanbois: Yes, I know there are 3rd party GC implementations that fix some of these issues.

10. Automated Garbage Collection: A significant portion of C++ code is dedicated to memory management. This meant faster time to market and lower bug count.

9. The Build Process: C++ builds are slow and complicated. Personal example: 20 hour full build in C++ compared to 7 minutes in Java.

8. Simplicity of Source Code and Artifacts: C++ splits source into header and implementation files. Artifacts are compiler-specific, but there are many of them. With Java, there's just one .java and just one .class.

7. Binary Standard: In addition to being loadable as a class by a JVM, a Java classfile can be used to compile against. Java defers platform-specific stuff to the runtime.

6. Dynamic Linking: No standard way to dynamically link classes in C++.

5. Portability: Java is portable with very little effort; C++ is portable in theory, but in practice you have to build another language (#ifdef'd types, etc.) on top of it. C++ has significant differences from vendor to vendor. Some unnamed major vendors have horrid support for the C++ standard, particularly templates.

4. Standard Type System: Java has specified, portable primitive types. C++ still has a hard time defining what a String is. Multi-threading? You must be joking. STL? Maybe some day. Basically nothing is standard!

3. Reflection: Full runtime capability to look at the runtime. C++ has optional RTTI, but no reflection. Enables extremely powerful generic frameworks. It gives you the ability to learn about, access and manipulate any object.

2. Performance: GC can make memory management much more efficient (slab allocators, escape analysis). This is because of modern architectures and the fact that Java can take advantage of multiple threads. Thread safe smart pointers in C++ are 3x slower than Java references. Hotspot can do massive inlining, which is very important for dealing with layers of virtual invocation.

1. Safety: Elimination of pointers (arbitrary memory access, ability to easily crash the process). With Java, there's no buffer overruns; code and data cannot be accidentally missed.

Honorable Mention: C++ Templates. Next time someone complains about Java Generics, make them read C++ Templates. They're fugly and extremely bloated.

10. Startup Time: The graph of initially loaded class in Java is pretty large. Conclusion: Not good for "instant" and short-running processes.

9. Memory Footprint: Java uses significantly more memory than C++, particularly for "small" applications.

8. Full GC Pauses: Sooner or later, there is a part of GC that can't be run in the background and can't be avoided. This causes havoc for distributed processes and things like real-time financial systems.

7. No Deterministic Destruction: No support for RAII. Cannot count on finalizers. There's not even a "using" construct in Java.

6. Barriers to Native Integration: Operating Systems are built in C/C++. APIs are typically in C.

And that's all Cameron could come up with. Turns out it was only a top 5 list.

So why did the shift from C++ to Java and C# happen? Because Shift Happens. First of all, Al Gore built this internet thing and the World Wide Web. We built a couple browsers with C++, but then we were done. Oh wait, we needed a web server too, so we built Apache. What about the other things? The things that run in the browser? There was no way we were going to run C++ in the browser b/c it was too unsafe. All the advantages that C++ had over Java didn't matter on the web. Startup time wasn't a concern when we left our app server running for months. Memory wasn't an issue because we had GB of RAM on our machines.

What about scripting languages? All the areas where C++ might have an advantage, scripting languages jumped in. They offered simplicity and approachability (hooks up to database, manages state on behalf of the user, produces HTML), rapid application development (no OO architectural requirements, save and refresh).

So what about cloud computing? Can we take what we learned from Java and C++ and apply them to what we see coming down the pipe now with cloud computing? What are we missing? What are the advantages that Java would be missing in a cloud environment?

The things missing from the VM: modularity, lifecycle and isolation. Lower memory footprint and predictable GC pauses. Things missing from the platform: distributed system as a system, provisioning and metering, cloud operating systems APIs, persistence (including key/value) and Map/Reduce-style processing. Finally, the application definition is missing packaging, resource declaration and security in a shared environment.

What's changed in the world since Java was introduced? Hardware virtualization, stateful grid infrastructure and capacity on demand ISPs (EC2). What's coming in Java? Modularization, NIO pluggable file systems, JVM Bare Metal and Virtual Editions. Conclusion: Java either steps up or something else will.

This was an enjoyable talk to listen to and I very much enjoyed Cameron's humor and slide pictures that supported it. As Dusty said, Cameron has a pretty clear picture of what the Java Roadmap should look like. Let's hope Oracle is listening.

Highly Interactive Software with Java and Flex

This morning at TSSJS, I attended James Ward's talk about Highly Interactive Software with Java and Flex. Below are my notes from his talk.

Application have moved from mainframes (hard to deploy, limited clients) to client/server (hard to deploy, full client capabilities) to web applications (easy to deploy, limited clients) to rich internet applications (easy to deploy, full client capabilities).

Shortly after showing a diagram of how applications have changed, James showed a demo of a sample Flex app for an automobile insurance company. It was very visually appealing, kinda like using an iPhone app. It was a multi-form application that slides right-to-left as you progress through the wizard. It also allowed you to interact with a picture of your car (to indicate where the damage happened) and a map (to indicate how the accident happened). Both of these interactive dialogs still performed data entry, they just did it in more of a visual way.

Adobe's developer technology for building RIAs is Flex. There's two different languages in Flex: ActionScript and MXML. ActionScript was originally based on JavaScript, but now (in ActionScript 3) uses features from Java and C#. On top of ActionScript is MXML. It's a declarative language, but unlike JSP taglibs. All you can do with MXML is instantiate objects and set properties. It's merely a convenience language, but also allows tooling. The open source SDK compiler takes Flex files and compiles it into a *.swf file. This file can then be executed using the Flash Player (in browser) or Air (desktop).

The reason Adobe developed two different runtimes was because they didn't want to bloat the Flash Player. Once the applications are running client-side, the application talks to the web server. Protocols that can be used for communication: SOAP, HTTP/S, AMF/S and RTMP/S. The web server can be composed of REST or SOAP Web Services, as well as BlazeDS or LC Data Services to talk directly to Java classes.

To see all the possible Flex components, see Tour de Flex. It contains a number of components: core components, data access controls, AIR capabilities, cloud APIs, data visualization. The IBM ILOG Elixir real-time dashboard is particularly interesting, as is Doug McCune's Physics Form.

Next James showed us some code. He used Flex Builder to create a new Flex project with BlazeDS. The backend for this application was a JSP page that talks to a database and displays the results in XML. In the main .mxml file, he used <s:HTTPService> with a URL pointing to the URI of the JSP. Then he added an <mx:DataGrid> and the data binding feature of Flex. To do this, he added dataProvider="{srv.lastResult.items.item}" to the DataGrid tag, where "srv" is the id of the HTTPService. Then he added a Button with click="srv.send()" and set the layout to VerticalLayout. This was a simple demo to show how to hook in a backend with XML.

To show that Flex can interact with more than XML over HTTP, James wrote a SOAP service and changed <s:HTTPService> to <s:WebService> and changed the "url" attribute to "wsdl" (and adjusted the value as appropriate). Then rather than using {srv.lastResult.*}, he had to bind to a particular method and change it to {srv.getElements.lastResults}. The Button's click value also had to change to "srv.getElements(0, 2000)" (since the method takes 2 parameters).

After doing coding in Flex Builder, James switched to his Census to compare server-execution times. In the first example (Flash XML AS), most of the time was spent gzipping the 1MB XML file, but the transfer time is reduced because of this. The server execution time is around 800ms. Compare this to the Flex AMF3 example where the server execution time is 49ms. This is because the AMF (binary) protocol streamlines the data and doesn't include repeated metadata.

To integrate BlazeDS in your project, you add the dependencies and then map the MessageBrokerServlet in your web.xml. Then you use a services-config.xml to define the protocol and remoting-config.xml to define what Java classes to export as services. To use this in the Flex aplication, James changed <s:WebService> to <s:RemoteObject>. He changed the "wsdl" attribute to "endpoint" and added a "destination" attribute to specify the name of the aliased Java class to talk to. Next, James ran the demo and showed that he could change the number of rows from 2,000 to 20,000 and the load time was still much, much faster than the XML and SOAP versions.

There's also a Spring BlazeDS Integration project that allows you to simply annotate beans to expose them as AMF services.

BlazeDS also includes a messaging service that you can use to create publishers and subscribers. The default channels in BlazeDS uses HTTP Streaming and HTTP Long Polling (comet), but it can be configurable (e.g. to use JMS). There's also an Adobe commercial product that keeps a connection open using NIO on the server and has a binary protocol. This is useful for folks that need more real-time data in their applications (e.g. trading floors).

I thought this was a really good talk by James. It had some really cool visual demos and the demo was interesting in showing how easy it was to switch between different web services and protocols. This afternoon, I'll be duking it out with James at the Flex vs. GWT Smackdown. If you have deficiencies of Flex you'd like me to share during that talk, please let me know.

The Cloud Computing Continuum with Bob McWhirter

This afternoon, I sat in a Keynote by Bob McWhirter at TSSJS 2010. Bob is the Chief Architect of Cloud Computing at Red Hat. Bob is "The Despot" at Codehaus, helped start Groovy and founded Drools. Below are my notes from his talk.

The cloud is not an either/or question. A scorched Earth strategy is not necessary to be in the cloud. The cloud is a continuum of technologies, many of those that you're already familiar with. You're used to web, messaging and storage. You can add just a little bot of cloud to your application at a time.

So what is the cloud?

It's the next logical step in application delivery.

How did we get to the cloud? First, we jammed a lot of servers into a closet (back in the .com days). That's a lot of stuff to deal with if all you want to do is deliver an internet-based service. Then we did some colo. The problem with colo was that it was still our stuff. Then we leased managed servers. With the cloud, we lease what appears to be servers (or services). This is a path we've all been taking to abstract the annoying bits away from hosting an internet-based service.

The typical diagram of a cloud has IaaS, PaaS and PaaS. IaaS abstracts away hardware. PaaS abstracts away services. SaaS abstracts away software.

Tenants of the cloud:

• The illusion of infinite resources.
• On-demand acquisition and provision.
• Someone else's responsibility.

Magicians provide the illusion of pulling a card out of your ear, but they don't actually do it. Because there are limits of what we can do. With on-demand requisitioning, there's no more purchase orders. There's no more waiting for delivery. No waiting for IT to rack it. Or install it. By having someone else manage your hardware, it's not your problem. There's clear lines of responsibility. This intentionally limits visibility into the implementation. Hopefully it's best-of-breed.

The Cloud is really just a mindset. Virtualization makes it affordable to make mistakes. Repeatedly. Each service is managed as an autonomous entity. Services are designed for scalability.

Architecture 101 give us a presentation layer, a business logic layer and a persistence layer. You can scale it by putting many instances on many servers. However, the truth is that most apps are a big ball of mud. You need to get your application in order, then figure out which parts really needs to scale. Is the web tier really where we have trouble? Painting HTML isn't all that hard.

You don't have to put everything in the cloud. The cloud is not a revolution. We still need containers for web things, messaging things, storage of things and other things. Containers still exist, they're just in the cloud.

From container to cloud
When you have an application and a database, there's not much to abstract away into the cloud. However, as soon as you notice your DB is slow, you'll add caching. Once you hit your machine's memory limit, you discover distributed caching systems. Once you've done this, you'll discover that the network isn't all that slow, especially compared to spinning disks. Then you realize that you don't even need the storage and you can keep everything in cache. From there, you move to a RESTful caching service. Then you call it a NoSQL Service so you can be buzzword-compliant.

As far as caching services, there's many available, but a lot of them are startups. However, the cloud does not have to mean external 3rd-party providers. Remember DBAs? It was their job to view the database as a service and to protect it. There's a good chance that we'll end up with DBAs for services. By turning caching into an independent service, it becomes subject to economies of scale.

The cloud is a mindset. It's an SOA approach that allows groups to specialize and optimize for scale.

So how do you implementing a local cloud? We already have great caching technologies. Bob, with his JBoss hat on, recommends Infinispan and its REST API. To get around network latency, you can still run your cloud on your LAN. You're essentially trading disk traffic for network traffic. You can use many hands (e.g. MapReduce) to make things happen quickly.

Besides caching, there's a number of other services that can be put in the cloud. For example:

• Messaging (REST-MQ
• Scheduling
• Security & Identity (OASIS, etc)
• Computation (query & otherwise)
• Transactions (REST-TX)
• Business Process Management
• Telephony (VOIP, SMS)

Your application becomes a stack of services, instead of a stack of software.

Higher-order business-logic services are also subject to cloudification. Ultimately, going into the cloud is not rocket science. The cloud does not turn everything on its head. We don't have to wait for new companies to develop new technologies. Startups may be the best consumers of the cloud, but might not be the best providers. We'll let the startups assume the risks for now. Until the 3rd party services have been proven, it's probably best to build your own cloud of services.

More than anything, the cloud has caused a return to fundamentals. Once your app is a collection of services, you can easily pick and choose what pieces you want to put in the cloud. This is where we're headed, whether you like it or not. As more apps become global-scape, you're going to run into these issues. By adopting a cloud mindset and architecture, your app can be prepared for scalability issues.

For more communication with Bob and his Cloud Evangelism, checkout StormGrind or follow him on Twitter.

Personally, I really enjoyed Bob's talk. It was by far the best keynote today, mostly because he told a story and did it elegantly with a nice-looking presentation. Not only that, but he provided the audience with a practical view of the cloud and ways that we can start using it in our applications today.

Update: You can find the slides from this session on SlideShare.

Software Quality: The Quest for the Holy Grail?

This afternoon, I attended a session on software quality by Jesper Pedersen at TSSJS. Jesper is a Core Developer at JBoss by Red Hat. He's the project lead of JBoss JCA, Tattletale, Papaki and JBoss Profiler 2. He's also currently the chairman of the Boston JBoss User Group. In this session, Jesper hopes to define basic requirements for a development environment and offer ideas on how to clean up a messy project.

Is software quality a friend or a foe? By implementing software quality processes, are you introducing unnecessary overhead? Development platforms are different today. We write a lot more business-specific code. We depend on standard frameworks for the core functionality. We depend on vendors to implement the standards correctly. We also depend on vendors to provide the necessary integration layer.

Since the platform is now a large slice of the pie, we must make sure we know where the issue is located. We must have proper integration tests; we must manage dependencies. Today, we must treat dependencies as if they are part of the application.

Defining the platform for your project helps narrow down the dependencies for your project. The platform is composed of corporate guidelines, standards, vendors and backend systems that you have to integrate with. Documentation is key for a successful project. Key documents types: User Guide, Developer Guide, API Guide, Architect Design, Implementation and Test.

It helps to define a project-wide configuration management system. Define a code-formatting guide will add consistency in your source tree. Also make sure you have separate build, test and execution environments. Use a Maven repository for your dependencies; both to support your project's artifacts as well as vendor artifacts.

"Maven today is an industry standard." -- Jesper Pederson

Define your tool chain as you would for your application. Back your Maven repository with SCM tools like Subversion or Git. For testing, use JUnit (unit testing), Corbertura (test coverage) and Hudson (continuous integration). Furthermore, you can add Checkstyle and Findbugs to verify coding conventions and find basic issues with code.

For the build environment, you need to make sure your dependency metadata is correct. Also, make sure you use the best practices for your given build tool. For example, with Maven and Ivy, it's a good idea to extract the version numbers into a common area of your pom.xml/build.xml so you can easily view all the versions in use. After you've done this, you can externalize the version information from the environment. Watch out for transitive dependencies as they can be tricky. Make sure you know what gets pulled in. Use enforcers to approve/ban dependencies or turn it off (Ivy). You can also vote for MNG-2315. Finally, snapshot dependencies are evil: define your release process so that releases are easy.

What can you do if your project is already a mess? Signs that your project is a mess: you look at your platform as a big black box, you use different dependencies than your deployment platform or you don't have integration tests for sub-systems or dependencies. To fix this, you can use a tool to get an overview of the entire project. Enter Tattletale.

Tattletale can give you an overview of your dependencies (Ant and Maven integration). It's a static analysis tool that doesn't depend on metadata, scanning your class files instead. Using Tattletale, you can produce a number of reports about your dependencies, what they're dependent on and what's dependent on you.

To maintain the lead in your project, make sure to define a checklist for each stage of your development cycle. Do reviews on documentation, architecture, component design and code. Enforce your rules of your project with your build system.

Jesper's final thoughts:

• Maintaining dependencies for a software project can be a tricky task.
• Using an Open Source platform as the foundation will ease the investigation of issues and increase trust.
• Defining a project-wide tool chain is key.
• Enforce all the rules on the project (better up-front than "fixing it" afterwards)

As Dusty mentioned, this session has a lot of good (basic) information, but there wasn't much new stuff. My team is using many of the technologies and practices that Jesper has mentioned. I guess that's validation that we're doing it right. I've heard of Tattletale, but never had a need for it since I haven't been on any "messy" projects recently.

What's Happening in the Java World?

This morning at TheServerSide Java Symposium I attended James Gosling's keynote. Below are my notes from his talk.

The unifying principle for Java is the Network - it ties everything together. Enterprise, Desktop, Web, Mobile, HPC, Media and Embedded. The most important thing in the Java world is the acquisition of Sun by Oracle. James is showing a slide of Duke in a fish tank with a "Snorcle!" title above it.

Obligatory statistics for Java:

• 15 million JRE downloads/week (doesn't count tax season in Brazil)
• 10 billion-ish Java enabled devices (more devices than people)
• 1 billion-ish Java enabled desktops
• 100 million-ish TV devices
• 2.6 billion-ish mobile devices
• 5.5 billion-ish smart cards
• 6.5 million professional Java developers

Java has become "Learn Once, Work Anywhere". Most college students worldwide have taken a Java course in school. James' daughter is in college but isn't interested in Java, mostly because her dad's name is all over the textbooks.

Java EE 6 was approved September 30, 2009. It was many years in the making; the result of large-scale community collaboration. It was built by hardware manufacturers, users, developers and academia. Because of all the politics involved, many engineers had to become diplomats. Most software engineers are from the wrong Myers-Brigg quadrant for this type of negotiation. Needless to say, the process was interesting.

New and Updated APIs in Java EE 6: Servlet 3.0, JAX-RS 1.1, Bean Validation 1.0, DI 1.0, CDI 1.0, Managed Beans 1.0, JASPIC 1.1, EJB 3.1, JPA 2.0 and many others. Also new is the Web Profile. It's the first Java EE profile to be defined. It's a fully-functional, mid-size stack for modern web application development. It's complete, but not the kitchen sink. It's what most people use when building a modern web application in Java.

Java EE 6 adds dependency injection with DI (JSR-330) and CDI (JSR-299). @Resource is still around, but an @Inject annotation has been added for typesafe injection. It has automatic scope management (request, session, etc.) and is extensible via a BeanManager API.

GlassFish is the world's most downloaded app server (1 million-ish downloads/month). GFv2 was the EE 5 reference implementation. GFv3 is the reference implementation for EE 6. But it's not just a reference implementation, it's a benchmark-winning mission-critical large-scale app server. The FCS was released on December 10, 2009.

Goals of Java EE: ease of use, right-sizing and extensibility. Now Roberto Chinnici (EE 6 spec lead) and another guy are on stage showing a NetBeans and GlassFish demo. With Servlet 3.0, you don't need a web.xml file, you just need a WEB-INF directory. There's a new @WebServlet annotation that lets you specify a "urlPattern" value for the servlet-mapping. A new @EJB annotation allows you to easily inject EJBs into your servlet. Roberto wired in an EJB, hit Ctrl+S and refreshed his browser and it all worked immediately. In the background, NetBeans and GlassFish did the redeployment and initialized the EJB container in milliseconds.

@ManagedBeans and @SessionScope and @Named are all part of CDI. When using @Named, the beans become available to JSTL and you can access them using ${beanName.property}. Interestingly, the CDI annotations are in difference packages: javax.annotation.ManagedBean and javax.enterprise.context.RequestScoped.

As David Geary mentions, it's great to see the influence that Ruby on Rails has had on Java EE.

Long demo of JEE6 in NetBeans. Spent quite a bit of time extolling the virtues of hot deploy. Thanks, RoR!

Now Roberto is showing us the admin console of GlassFish and how modular it is. He's installing a JMS module, but it's interesting to see that there's a Ruby Container installed by default. Apache Felix is the underlying OSGI implementation used by GlassFish. You can telnet into it and see the status of all the bundles installed. After installing the full-profile, Roberto shows that you can restart the server from the console.

Isn't the whole point of OSGI that you don't have to restart anything!?

The GlassFish management console is definitely impressive and visually appealing. Apparently, it's extensible too, so you could easily write plugins to monitor your application and provide memory statistics.

Changing topics, one of the things that nice about Java is its a two-level spec. The important thing in the Java world isn't the language, it's the virtual machine. The magic is in the VM! Scala, Ruby/Rails, Groovy/Grails, Python, PHP, JavaScript, JavaFX and many others. In the same breath of talking about Java.next languages, James mentioned JavaFX Script. It's a new declarative scripting language for GUIs. It's similar to Flash or Silverlight, but it's much better because it has the Java VM under it.

At the current rate that we're going with CPUs and cores, there's a good chance we'll have 5220 cores on our desktops by 2030. If you find the concurrency libraries scary, get over it.

For the rest of talk, James talked about what he's hacking on these days. He's helping build an Audi TTS for the Pikes Peak Road Rally in Colorado. The goal is to figure out a way to keep the vehicle above 130 MPH for the whole race. Sounds like a pretty cool project to me.

I don't think there was a whole lot of new information covered in James' talk, but I really do like Java EE 6's Web Profile. However, I think it's something most of the community has been using for many years with Tomcat + Spring + Hibernate. Now it's simply been standardized. If you happen to work at one of those companies that frowns on open source and smiles at standards, you've finally caught up with the rest of us.