Posts for query "jnosql", by date descending

Another Project: XPages Jakarta EE Support

  • Jun 3, 2018

In my dealings with JNoSQL recently, I’ve been delving more into the world of modern Jakarta EE/Java EE/J2EE development, particularly the magic land of CDI.

The JEE stack tends to be organized as a collection of specs and implementations, many of which are really independent of each other and the underlying platform, making them pretty portable onto any reasonably-recent JVM. Now that Domino is actually on a reasonably-recent JVM, that makes it a workable target! So I decided to create a side project to bring some of JEE to XPages.

XPages has always been “sort of Java EE” - you don’t really have the full stack, and it’s far behind on the components that it does have, but a lot of the concepts are there. Of particular interest are managed beans and expression language.

CDI and Managed Beans

The XPages stack contains what amounts to a priomordial version of CDI. Since the release of XPages, JSF improved on the original faces-config.xml declaration method to add annotation-based declarations, and then CDI is something of a codification and expansion of that into the full Java world.

My project uses the Weld reference implementation of CDI to create a CDI context for each XPages app that opts in, allowing it to use annotations on classes to declare beans and properties:

@ApplicationScoped
@Named // or @Named("applicationGuy")
public class ApplicationGuy {
    public void getFoo() {
        return "hello";
    }
}

These can then be used like normal managed beans in an XPage:

<xp:text value="#{applicationGuy.foo}"/>

The project’s README contains some further examples.

I went with the Java SE implementation of Weld instead of the pre-built servlet or OSGi packages since those are a little too smart for this use: they pick up on the fact that they’re in a JSF environment, but expect newer versions of the servlet spec and JSF.

Expression Language

Since its original release, EL went through a similar standardization process as CDI and is now at version 3.0 and is distinct from JSP and JSF. As anyone who has tried to call a method on a bean in EL has found out, the XPages EL implementation lags pretty far behind, at the JSF 1.0/1.1 level. Since that time, it sprouted parameters and “projection” and is essentially a tiny scripting language now.

My project uses GlassFish’s EL implementation to outright replace the stock EL interpreter for apps making use of it. I added some affordances to IBM’s customized data support, so it’s intended as a drop-in replacement:

<xp:text value="${dataObjectExample.calculateFoo('some arg')}"/>

<xp:text value="#{el:requestGuy.hello()}"/> 

Note the “el:” prefix in the runtime-bound expression: that’s to get around Designer’s validation of runtime EL expressions.

So… Why?

That’s a good question! The first two reasons are “because it’s fun” and “to learn more about JEE”, but there’s also practical value for this sort of thing.

XPages is moribund, and that leaves Domino developers with a few options:

  • Go back to LotusScript. The iPad Notes client makes this a terrifyingly-practical option, but it’s soul death.
  • Go to JavaScript (or another platform). This is another route HCL is pushing, and it’s entirely valid: Node is a great platform with excellent support and momentum.
  • Go to modern Java.

For anyone who has invested a lot of time and brainpower in XPages over the years, that last one particularly appealing, and projects like this can help you get there. If you have a large XPages code base, as I do with one of my clients, it makes a lot more sense to work on that in such a way that it gradually becomes less XPage-dependent while avoiding the trap of a full rewrite in another language.

Many of us have already done something of this sort: JAX-RS is another JEE standard, and the Wink implementation in the Extension Library, though also aging, accomplishes this same sort of task. Especially if your services don’t reference Wink explicitly and write just to the spec, they are very portable.

That portability - of code and skillset - is critical. Say you have a class like this:

import javax.inject.Inject;
import javax.ws.rs.Path;
import javax.ws.rs.GET;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

@Path("/issues")
public class IssuesResource {
    @Inject IssueRepository issueRepository;

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Response get(@QueryParam("category") String category) {
        return issueRepository.find(category).stream()
            .map(this::doSomething)
            .skip(3)
            .collect(this::toResponse);
        }

‚Äč     // ...
}

Which Java platform is that targetting? What’s the data storage mechanism? Who cares? This class certainly doesn’t. That could just as easily be Domino reading from an NSF or (as is actually the case in the example’s source) Tomcat with Darwino.

What’s Next?

Truthfully, maybe not much. Though JEE contains a whole raft of technologies, these two were the ones that scratch my immediate itch. We’ll see, though - the skill portability of erstwhile XPages developers is critically important, and I think that this is another one of the paths that can get us where we need to go.

Lessons From Writing a JNoSQL Driver

  • Dec 30, 2017

The other day, I decided to start up a side project to write an app for my Stars Without Number game in Darwino. Like back when I wrote a forum/raiding app for my WoW guild, I like to use this kind of opportunity to try new technologies and flesh out my skills in existing ones.

One such tech I've had my eye on for a bit is JNoSQL, which is a framework for integrating with NoSQL databases in Java. It's along the lines of Hibernate OGM, but intended to avoid the pitfalls of the relational/NoSQL that came with trying to adapt JPA directly to NoSQL databases. JNoSQL promised to be much easier to implement for a new database, so I decided to give it a shot.

JNoSQL

JNoSQL is split into two paired components, cleverly named Diana (the driver side) and Artemis (the model/integration side). The task of writing a driver for a new database is pretty well-contained: pick the database type(s) you want to implement (out of key/value, column, document, and graph) and implement about half a dozen interfaces. This is in stark contrast from when I took a swing at writing a Hibernate OGM driver, where the task was significantly more daunting. The final result is only ten Java files, with a chunk of them being utility classes for code organization.

It's a young project - young enough that the best version to run right now is 0.0.4-SNAPSHOT - but it functions well and it's been taken under the wing of the Eclipse foundation, which builds some confidence.

Implementation

Though the task was small, there were still a couple initial hurdles to getting going.

To begin with, I decided to start with the Couchbase driver - this certainly made the overall task easier, since Couchbase's semantics are very similar to Darwino's, but it also meant that I had to be wary of which parts of the codebase were really about implementing a Diana driver and which were Couchbase-isms. Fortunately, this was much easier than the equivalent work when I adapted the CouchDB Hibernate OGM driver, which was a sprawling codebase by comparison.

More significantly, though, it's always tough coming in to modify a codebase written by a single person or small team and learning as you go. The structure of the code is clean, but not quite my normal style (in part because Domino kept me from diving into Java 8 streams for so long), and I also had to ramp up quickly on the internal concepts of Diana. Fortunately, this was mostly easy, since the document-DB driver scaffolding is purpose-built, the hooks are straightforward and the query semantics were extremely easy to adapt. The largest impediment was getting used to the use of the term "Document", which internally refers to a key/value pair, while "DocumentEntity" is closer to the expected meaning.

Like the core implementation, the test suite I adapted from Couchbase was also pleasantly svelte, covering the bases without being an onerous nightmare to convert. Indeed, most of the code I added to it was the Darwino app scaffolding just for the test runtime.

Putting It Into Practice

Once the driver was written, I was hit by a bit of a personal curveball when I went to implement some actual data models. The model side, Artemis, is heavily wrapped together with CDI, which is a Java EE thing that, as I gather, handles managed beans, separation of implementation, and variable injection. This is a pretty normal thing for Java EE developers, but XPages's "don't call it Java EE" environment didn't introduce me to this aspect. As such, the fact that the documentation just kind of casually tossed around CDI terms and annotations threw me for a bit of a loop trying to determine what was what was required and what was just an idiom.

I eventually determined that I could use the reference implementation, Weld, without necessarily going whole-hog on Java-EE-everything. I'm a bit wary of what this bodes for whether I'll be able to use JNoSQL in Darwino on mobile devices, but I'll cross that bridge when I come to it. Once I got a bit of a handle on what Weld is and how to use it in unit tests (hint: make sure you have beans.xml files!), I was able to start writing my model objects and testing them.

Doing It Again

The fact that the bulk of my implementation work ended up being on the app side with CDI goes to show that the Diana driver model really shines. It got me thinking about how difficult it would be in the future, say to write a driver for Domino. There'd be some hurdles - Domino's lack of nested objects and antiquated querying mechanisms would need replacing - but the core task wouldn't be too bad. I don't know if I'd have a need for it, but it's nice to keep in mind as potential future small project.

All in all, I'm optimistic about the use of this. I'd love for Darwino to integrate as smoothly as possible into whatever standard environments it can, and this is one more step in that direction. I'll know as my side app takes shape how much this ingrains itself into my actual work.