Small Aside: Writing Agents With Java 5+ Features

Nov 26, 2019, 3:46 PM

Tags: designer java

The topic of using Java 5+ language features in agents came up recently in the OpenNTF Slack room (use this invitation link if you haven't already joined!), and I think that it's one of those topics that's worth making a post about for posterity's sake.

For historical and compatibility reasons, the default compiler language level for newly-created agents, at least in the absence of the JavaCompilerTarget notes.ini setting, is Java 1.3:

Java Agent Compiler Properties

This is laughably out-of-date, and doesn't even support 15-year-old features like generics. Accordingly, if you take a piece of code from my last post, you'll end up with a couple errors:

Java agent compilation problems

It recognizes the Java 7+ classes, since it's still backed by a Java 8 JDK, but it complains about try-with-resources and the use of varargs.

Setting the Compiler Level

The fix for this is to change the compiler compliance level for your agent project. Depending on the type of problem, you may be given an Eclipse quick fix option if you hover over the red-underlined text:

Eclipse quick fix

If you don't have that option (for example, there's no such option for the Files.createTempFile vararg problem), you can alternatively go to the "Package Explorer" view, find the temporary project for the agent (named something like "foo.nsf.Some Agent.ja"), and go to Properties. In there, you can go to the "Java Compiler" settings, make sure the "Compiler compliance level" is the level you want, and then check "Use default compliance settings":

Project compiler at 1.8

When you do this and next save the agent, you'll be greeted with this Designer-specific message box:

Java compiler backward compatibility warning

This is good to see, since it shows that Designer picked up the change and will write it into the agent note in items named $JavaCompilerSource and $JavaCompilerTarget. That's the part that really counts, since it's what Designer uses to re-construct the Eclipse project in the future.

Note, though, that the title of the message box is a reminder about an important aspect: if you set the target compiler level to 1.7 or above, then your agent will not run on Domino servers before 9.0.1 FP8. So, if you're using one of those for some reason, take care about the language features you're using. The other breakpoints, if you're working with some really-legacy servers, are Java 1.4 being added in 7, 1.5 added in 8, and 1.6 added in 8.5.

Dealing With Errors

Depending on your Notes version (I suspect this problem cropped up in 9.0.1FP10 and seems to be gone in the V11 beta), changing your compiler level may result in "forbidden reference" errors for basic things like the lotus.domino classes.

If you hit this, the quickest fix is to modify your settings in Designer's preferences, in the "Java" → "Compiler" → "Errors/Warnings" section:

Setting to ignore forbidden references

If you set "Forbidden reference (access rules)" in the "Deprecated and restricted API" section to "Ignore", the problems should go away. I'm not actually sure why this problem crops up (perhaps something to do with the structure of Notes.jar), but it was fairly consistent for me for a while.

With all that set, though, you should be free to use up to Java 8 features in agents (and web services, probably) to your heart's content.

Writing a Java NIO Filesystem, Part 1

Nov 25, 2019, 3:09 PM

Tags: java java-nio
  1. Writing a Java NIO Filesystem, Part 1

My recent project, the NSF SFTP File Store consists of two main parts: the SFTP server itself (powered by Apache Mina) and a Java NIO filesystem implementation. I casually mentioned the latter in my introductory post, but I think it's an interesting topic that warrants a post or two of its own.

Introduction to NIO

The term "Java NIO" refers to the non-blocking IO package added in two parts across Java 6 and 7 and can be considered a refresh of previous capabilities in a similar way to the Collections API in Java 2 replaced the handful of original collection classes.

The initial (and larger) part of it added in Java 6 added better capabilities for dealing with all sorts of "byte stuff": buffers of arbitrary types, smoother character-set handling, more-flexible streams, and so forth. I dealt with these constructs a while ago with the "nsfdata" package in ODA. In that case, it proved very useful for dealing with in-memory representations of Notes Composite Data, which is best dealt with as a navigable array of differently-sized structures.

The java.nio.file package was added in Java 7 and is a refresh of the older java.io.File/java.io.FileOutputStream/etc. system. It interacts well with the previous NIO stuff, but can actually be thought of as a distinct thing, despite its shared naming. This package changes around the mechanics of the original filesystem API, and I remember finding it kind of grating when I first encountered it. It's all in service of being more flexible, though, and it's one of those things where repeated exposure ended up making the older API feel weird and wrong.

Using the NIO Filesystem API

Before I get to the actual implementation of a backing filesystem, I think it'll make sense to show some examples of using the NIO filesystem API, especially since these can (and should) be used in any Java-based application today.

When the new classes were added, the older File class was augmented with a method to convert it to a java.nio.file.Path and vice-versa:

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File foo = new File("/some/path/to/file");
Path fooPath = foo.toPath();
File fooFile = fooPath.toFile(); // for older-API interoperability

The Path interface is a very-lightweight and implementation-neutral representation of a path. Unlike the File class, it doesn't have methods for actually interacting with the filesystem. In fact, pretty much all you can do with it specifically is get other Paths based on it:

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Path foo = Paths.get("/some/path/to/file");
Path parent = foo.getParent();   // "/some/path/to"
Path child = foo.resolve("bar"); // "/some/path/to/bar"

The primary way you use Path objects is via the Files utility class, which provides not only the methods you may be familiar with from File but also some additional ones like getting input and output streams:

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Path foo = Files.createTempFile("test", ".tmp");
try(OutputStream os = Files.newOutputStream(foo, StandardOpenOption.TRUNCATE_EXISTING)) {
  os.write("hello".getBytes());
}
try(BufferedReader r = Files.newBufferedReader(foo)) {
  System.out.println("file contains " + r.readLine());
}

Here, you can see a couple things going on:

  • Files.newOutputStream replaces FileOutputStream, and so the object you assign it to should be declared as just OutputStream.
  • Many of the Files methods take zero or more open/move/etc. options, and they can be a little odd at first. The method parameters are declared as e.g. OpenOption, but the actual options are available in the StandardOpenOption enum. This is to allow for arbitrary extensions for custom filesystems. For example, you might write a custom option to force creating a backup version of the file before writing.
  • I'm using the try-with-resources syntax from Java 7 here. That isn't actually related to NIO except in that it came in the same release, but it's great and you should use it.

The Files class also contains methods for listing files and walking file trees, which operate with Streams (as of Java 8) and callbacks. For example, this bit from the NSF ODP Tooling walks a file tree using the callback method and stores it in a ZIP file:

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try(OutputStream fos = Files.newOutputStream(result)) {
  try(ZipOutputStream zos = new ZipOutputStream(fos, StandardCharsets.UTF_8)) {
    zos.setLevel(Deflater.BEST_COMPRESSION);
    Files.walkFileTree(path, new SimpleFileVisitor<Path>() {
      @Override
      public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
        if(attrs.isRegularFile()) {
          Path relativePath = path.relativize(file);
          String unixPath = StreamSupport.stream(relativePath.spliterator(), false).map(String::valueOf).collect(Collectors.joining("/")); //$NON-NLS-1$
          ZipEntry entry = new ZipEntry(unixPath);
          zos.putNextEntry(entry);
          Files.copy(file, zos);
        }
        return FileVisitResult.CONTINUE;
      }
    });
  }
}

Next Up: Implementation

In my next post, I'll get into some specifics of implementing a filesystem using this framework as well as some of the implications of how flexible and straightforward it is.

Options for the Future of the Domino Open Liberty Runtime

Nov 18, 2019, 3:57 PM

Tags: java liberty
  1. Options for the Future of the Domino Open Liberty Runtime
  2. Next Steps With the Open Liberty Runtime
  3. Rapid Progress in Open-Liberty-Runtime Land

I've been thinking lately about what I can do with the Open Liberty Runtime project. If you're not familiar with it, the gist of it is that it gloms the Open Liberty Java/Jakarta EE app server onto Domino to allow deploying up-to-date WAR-based apps "to Domino", sharing the server's access to NSFs.

In its current form, it's serving me reasonably well: this blog is running on it, for example, and writing the SFTP server to target it has been a delight. I've been tracking a set of issues about it, mostly relating to improving the administration/deployment side as it is in ways that would improve my current use. There are some more-out-there ideas like running apps from NSFs, but for the most part it's been focused on "a JEE server attached to Domino".

Slightly-Tweaked Model

But what I've been thinking about lately is tweaking the model a bit to be less like "a new HTTP runtime" and more like a series of related servers, which would then be proxied to. This is in line with what Liberty has been trending towards anyway. Though it started out as essentially a cleaned-up WebSphere monolith, the fact that it's been targeted at cloud-service use has meant that it's been aggressively tuned to allow you to include only the specific features you need, with the idea that there will be many instances of Liberty running, one per app. This is also seen in their relentless push for faster startup times, something that only matters if you plan to start up instances of the server very frequently.

My Runtime project technically supports this model currently. Though it uses a single Liberty runtime download, the main Servers list is geared towards creating multiple running servers with their own app sets, which end up being distinct processes:

Open Liberty Admin Servers view

So one could hypothetically put dozens of servers in here and use it as I've been describing. Other than providing that capability, though, the tooling doesn't really help you much: in particular, it would do nothing to alleviate the problems of conflicting port mappings or unifying all of these apps into a single front. I did a little work making a reverse-proxy webapp, but it's really meant for the case of having one Liberty server with all of your apps, and wouldn't have any meaning in a many-server setup.

One option I've been considering here is giving the server side of this some knowledge of and control over the HTTP ports used by the individual Liberty servers, so that it could assign random ones automatically. Then, I'd also be able to add on a dynamically-configured reverse proxy that would know about these different running servers and could route requests automatically.

Other Runtimes

On top of that, there's nothing about the project that's really inherently tied to Open Liberty as such. It currently assumes that that's the runtime, but the only way it interacts with it is by pouring files out to the filesystem and then running some known shell scripts. There's nothing stopping such a setup from also gaining a bit of knowledge about, say, Node, Swift, or any number of other runtimes. Things would get progressively weirder the further you get from Java when you want to access the Domino runtime, but hey, that's what the C API is for!

Reinventing the Wheel

While mulling this over, though, I did realize one thing: I'm essentially describing a jankier version of Kubernetes. For the most part, the problem of running disparate apps with their own runtimes and needs managed by a central server is solved by that and Docker. This project would be a bit different in that the apps would automatically inherit a Domino runtime and would also (usefully) maintain clustered/replicated configuration by way of the Domino server backbone, so it's not exactly the same thing. And, while HCL is pushing for a Dockerized future, the pieces aren't there yet and won't fully be for a while: while Domino-on-Docker is a thing technically, "many Notes-runtime apps with many server IDs" for NRPC use is a licensing minefield, and the gRPC bindings are currently painfully limited in both capability and language support.

So I likely would be best off just letting time (which is to say, HCL) solve the fancier problems and just focusing on the Runtime's original job of being a better Java app server for Domino. I do think it would be useful to better support the one-server-per-app approach, especially for a hypothetical case of wanting to deploy an XPages app in one Liberty server but then a JSP or JSF app in another, and that'll take a better reverse proxy.

I think it's good to mull over, though. This already provides a good path to better app dev with Domino, and smoothing that out more will make my life all the better and will hopefully be useful to others.

Quick-Tip Thursday: Avoid Future Base64 Trouble In Java

Nov 14, 2019, 2:35 PM

Tags: java sntt

TL;DR: Don't use com.ibm.misc.BASE64Encoder or com.ibm.misc.BASE64Decoder.

If you've been doing Java development for a while, you've likely run into a situation where you need to Base64-encode or -decode something. It's used commonly in MIME documents, data URIs, and various other areas typically related to data transfer.

Unfortunately, using Base64 in Java was awkward for a long time, with no natural choice in the core JDK until Java 8. The trouble over the years, though, is that there are choices in previous releases, and it became somewhat common in the community to use sun.misc.BASE64Encoder for this need. The problem with that is that sun.* packages are officially not part of the JDK and can't be relied upon to exist in every Java implementation. Unfortunately, a combination of a lack of enforcement of this in the tooling and the fact that those classes are in practice pretty universal has let them creep into Java code.

On the Domino side, we have a second problem: com.ibm.misc.BASE64Encoder.

Sidebar: The Different Flavors of Java

For the most part, setting aside Android, it's safe to think of "Java" as a monolithic entity, where having a JVM of a given version number on one system will be equivalent to the same on another. There are subtle differences, though, and several vendors have long maintained their own variants of Sun/Oracle's JVM (which is named HotSpot).

IBM has maintained one such variant, called J9, and infused all of their Java-using products, Domino included, with it. J9 has since been open-sourced and donated to Eclipse and, renamed to OpenJ9, has carved out a niche for itself by being particularly lean and speedy to spin up.

The Snag We Hit With J9

For the most part, the differences in JVM flavors don't matter to developers, but IBM played a bit of a trick on us by making duplicates of some sun.* classes under the com.ibm.* package. Unlike sun.*, which at least has a little community knowledge of being internal-only (and also just looks odd compared to standard classes), com.ibm.* has no such connotation, and there's nothing in Designer or the classes themselves to indicate that com.ibm.misc.BASE64Encoder (internal and non-portable) is any different from, say, com.ibm.commons.util.io.base64.Base64 (portable via IBM Commons).

So, over the years, use of that class has crept into XPages and Java agent code - it does the job and it's always been safe to assume that Domino-the-IBM-product would use J9-the-IBM-JVM. Domino isn't an IBM product anymore, however, and, to add to potential future trouble, even OpenJ9 builds from AdoptOpenJDK don't come with those com.ibm.misc.* classes.

The upshot is that, if your Java code were to run on a JVM other than an fully-IBM-style one (whether intentionally or otherwise), you're liable to run into trouble with code that casually used those JVM-internal classes.

The Options

If you're running a version of Domino using Java 8 (9.0.1FP8+), which you'd darn well better be at this point, you're in luck: the built-in java.util.Base64 class has a nice API and is guaranteed to be present on every JVM. This is your best bet, since it doesn't require any other dependencies beyond the core JDK and it has some nice features like variant encoders for MIME- and URL-safe use.

If you're targeting a version of Domino that still uses Java 6 (don't), you do have one other safe-enough option that's available in both XPages and Java agents: javax.xml.bind.DatatypeConverter. This class is technically part of the JAX-B specification but is included in JVMs from version 6 through version 10. This is less of a clean choice than the java.util.Base64 class both because it's not as nice of an API and because use on Java 11+ will require bringing in an external dependency. Still, if you're stuck on an old release, it'll at least get you through any potential rough patches in the near future.

Finally, in XPages, you have the aforementioned com.ibm.commons.util.io.base64.Base64 class, which will continue to be present due to being included in a base library of the XPages stack, but which is rendered obsolete by java.util.Base64.

So I recommend taking some time to look through any running Java code you have for this potential hiccup and making the switch. It's admittedly a little awkward to do, but it's still a good idea.

Writing Domino JEE Apps Outside Domino

Nov 8, 2019, 6:47 PM

In my last post, I mentioned that I decided to write the File Store app as a Jakarta EE application running in a web server alongside Domino, instead of as an app running on the server itself. In the comments, Fredrik Norling asked the natural question of whether it'd have been difficult to run this on the server, which in turn implies a lot of questions about deployment, toolkits, and other aspects.

Why Not

My immediate answer is that it would certainly be doable to run this on Domino, but the targeted nature of the app meant that I had some leeway in how I structured it. There are a couple reasons why I went this route, but most of them just boil down to not having to deal with all the gotchas, big and small, of doing development on top of Domino.

As a minor example, I wanted to add some configuration parameters to the app, and for this I used MicroProfile Config. MicroProfile Config is a small spec that standardizes the process of doing key-value-based configuration, allowing me to just say that I want a named value and let the runtime pick it up from the environment, system properties, or a config file as necessary. It wouldn't be difficult to write a configuration checker, but why bother reinventing the wheel when it's right there?

Same goes for having the SFTP server load at startup and be running consistently. If I did this on Domino, I could either put it in an NSF-based XPages app with an ApplicationListener and depend on the preload notes.ini parameter, or I could go my usual route and use an HttpService that manages the lifecycle. Neither route is difficult either, but they're both weirder and more fiddly than using servlet context listeners in a normal JEE app.

And then there's just the death by a thousand cuts: needing to use Tycho to build, having to deal with Eclipse Target Platforms, making sure anything using reflection is wrapped in an AccessController block to avoid Java policy issues, the nightmare of dependency management, the requirement to use either Designer or the okay-but-still-cumbersome Domino HTTP restart development cycle, and on and on. With a JEE app, all of those problems disappear into thin air.

The Main Hurdle

All that said, there's still the hurdle of actually implementing Notes native API access outside of Domino. At its core, what I'm doing is the same as what has been possible for years and years, initializing a Notes/Domino runtime in a secondary process. The setup for this varies platform by platform but generally involves either setting a couple environment variables for your process or (as is the case with the Domino Open Liberty Runtime) spawning the process from Domino itself.

Beyond setting up your process's environment, there's also the matter of initializing each thread of your app. On Domino, all threads are inherently NotesThreads, but outside of that there's some specific management to be done. You can call NotesThread.sinitThread() and NotesThread.stermThread() manually or run your code in specifically-spawned NotesThreads. I largely do the latter, making use of an ExecutorService to handle maintaining a thread pool for me. I then added some supporting code on top of that to let me run blocks of code as an arbitrary named user while retaining a cached set of sessions. That part wouldn't really be necessary if you're writing an app that doesn't need to act as different user names, but it's handy for something like this, where incoming connections must run as a user to enforce security fields properly.

Philosophical Advantages

Beyond my desire to avoid hassles and get to use modern Jakarta EE goodies, I think there are also some more philosophical advantages to writing applications this way, and specifically advantages that line up with some of HCL's stated long-term goals as well. Domino has long been a monolith, and that has largely served it well, but keeping everything from the DB all the way up through to the app-dev stack in the same bag means you're often constrained in your toolkits and deployment choices. By moving things just outside of the main Domino tower, you're freed up to use different languages and techniques that don't have to be integrated and maintained in the core. This could be a much larger jump than I'm doing here, and that's just what HCL has been pushing with the AppDev Pack and the associated Node.js domino-db module.

I think it's beneficial to picture Domino more as a dominant central core with ancillary servers and apps running just adjacent to it - not a full-on Microservices architecture, but just a little decentralized to keep areas of concern nice and separate. Done well, this setup is a lot more flexible and fault-tolerant, while still being fairly straightforward and performant. It's also a perfect match for a project like this that's geared towards implementing a new protocol - it doesn't even have to worry about HTTP SSO or reverse proxies yet.

So I think that this is where things are heading anyway, and it's just a nice cherry on top that it also happens to be a much (much, much) more pleasant way to write Java apps than OSGi plugins.

Another Side Project: NSF SFTP File Store

Nov 5, 2019, 9:12 PM

When I Know Some Guys kicked off, we bought a couple of Transporter devices to handle our file-syncing needs without having to rely on Dropbox or another hosted service. Unfortunately, Nexsan killed off Transporters a couple years back, and, though they still kind of work, it's been a back-burnered project for us to find a good replacement.

Ideally, we'd find something that would handle syncing data from our various locations transparently while also allowing for normal file access through some common protocol. Aside from the various hosted commercial services, there are various software packages you can run locally, like OwnCloud and NextCloud. I even got a Raspberry Pi with a USB hard drive to tinker with those, though I never got around to actually doing so.

Yesterday, though, I realized that we already have a fleet of privately-owned servers that replicate seamlessly in the form of our Domino domain. They also, conveniently, have nice capabilities for blob storage, shared user authentication, and fine-grained access control. What they didn't have, though, was any good form of file protocol. I'm pretty sure that Domino still has WebDAV built-in, but that's just for design elements. Years ago, Stephan Wissel created a project that works with file attachments, but that didn't cover all the bases I wanted and I didn't want to adopt the code base to extend it myself. There's also Karsten Lehmann's Mindoo FTP Server from around the same time, but that was non-SSH FTP and targeted at the local filesystem.

So that meant it was time for a new project!

The Plan

I initially looked at WebDAV, since it's commonly supported, but it's also very long in the tooth, and that has led to all of the projects implementing that being pretty old and cumbersome as well.

Then, I found the Apache Mina project, which implements a number of server protocols, SSH included, and is actively maintained. Looking into how its SFTP support works, I found that it's shockingly simple and well-designed. All of the filesystem access is based on the Java NIO packages added in Java 7, which is a pluggable system for making arbitrary filesystems.

Using SFTP and SCP means that it'll work with common tools like Transmit and - critically - rsync. That means that, even in the absence of an custom app like Dropbox, mobile access and syncing with a local filesystem come "for free".

The Project

So out of this was born a new project, NSF File Server. Thanks to how good Mina is, I was able to get a NIO filesystem implementation and SFTP+SCP server up and running in very little time:

Screen shot of the SFTP server in Transmit

In its current form, there aren't a lot of tricks: the files are stored as attachments to normal documents in a "filestore.nsf" database with two views, which allow for directory-contents and individual-file lookup while also being pretty self-explanatory to a Notes client. I have some ideas about other ways to structure this, but there's an advantage to having it be pretty basic:

Screen shot of the File Store NSF

Similarly simple are the authentication mechanisms, which allow for both password and public-key authentication based on the HTTPPassword and sshPublicKey fields in a person document, respectively (and maybe via LDAP in directory assistance? I never remember the mechanics of @NameLookup).

The App

Because this is a scratch-our-itch project and I'm personally tired of dealing with Domino's OSGi environment, the app itself is implemented as a WAR file, expected to be deployed to a modern Jakarta EE server like my precious Open Liberty. Conveniently, I have just the project for that as well, making deploying NSF-accessing WARs to Domino a bit more reasonable.

For now, the app is faceless: the only "web app" bits are some listeners that initialize the Notes environment and then spawn the SSH server. I plan to add at least a basic web UI, though.

Future Plans

My immediate plan is to kick the tires on this enough to get it to a point where it can serve as its original goal of a syncing SFTP server. I do have other potential ideas in mind for the future, though, if I feel so inspired. Most of my current logged issues are optional enhancements like POSIX attribute support, more-efficient handling with the C API, and better security handling.

It's also a good foundation for any number of other interfaces. A normal web UI is the natural next step, but it could easily provide, for example, S3 API compatibility.

For now, though I haven't gotten around to uploading a build to OpenNTF yet, feel free to poke around the code and let me know if any ideas strike your fancy.

CollabSphere 2019 Slides

Nov 2, 2019, 1:04 PM

I've uploaded my slides for my session at CollabSphere: "Preparing Your XPages Applications for a Changing Future":

CollabSphere 2019 - Preparing Your XPages Applications for a Changing Future

While working on the presentation, I realized that pretty much all of the slides in there warrant blog posts of their own, so, as I have the time and wherewithal, I plan to expand on the topics a good deal in the weeks to come.

Additionally, Howard Greenberg uploaded the slides from our shared presentation ("shared" in the sense that he did 90% of the work), "Let's Calendar That":

Dev112 let's calendar that from Howard Greenberg