In this probably-final entry in the series, I'd like to muse a bit about possible future improvements and additions to the compiler and the NSF ODP Tooling generally. For the most part, the big-ticket future additions seek to answer one question:

Could this be used to replace Designer?

The quick answer is "yes, it could", but that would take a lot of work. There are a couple things inherent in the task and specific to my implementation that both help and hinder this kind of thing.

Notes Runtime

The biggest stumbling block is the hard requirement on a Notes or Domino runtime initialized for the current process. Being able to use C API calls is required by both my code and some of the underlying XPages bits, and that means initializing the runtime. The good news here is that it doesn't require any specific Notes-based program - it can be run with either the libraries that come with Notes or Domino, and it doesn't require Designer at all. That loosens things up a bit, but still means that one of the supported platforms is obligatory at some step of the process.

Even on a supported platform, though, it's not just as easy as calling an init function - the process's environment needs to be set up specifically to know about the Notes program and data directories, and this varies platform-by-platform. This means that it wouldn't be straightforward to have, for example, an Eclipse plugin that initializes the process, since it would depend on initialized environment variables and loading paths implicitly referenced by lower layers, and over which the programmer doesn't have much control after the fact.

The good news here is that the tooling is already designed to support remote work for compilation and export, both truly remote and with the local Equinox runners. For a true IDE experience, the communication between the IDE and compiler would have to be more complex than the "tell the compiler what to do and hear messages back" simple mechanism it has now, but it'd still be a natural evolution.

OSGi Runtime

The requirements posed by compiling complicated XPages applications presents a similar dependency as above, but on an Equinox environment. Though it's possible to fake the basics of OSGi for known plugins, that wouldn't work for arbitrary third-party libraries.

For integration in Eclipse, this wouldn't necessarily mean any new work - Eclipse is already the premier Equinox product, and so it supports what XPages compilation needs innately. However, Eclipse wouldn't be the only target; any work done here should work with other IDEs like IntelliJ, but also continue to work IDE-free via a Maven or Gradle environment.

So this ends up being another strong argument for retaining the "separate process" model that already exists.

Incremental Compilation

Beyond retaining the runtime requirements, the big thing would be a switch to supporting incremental compilation. Currently, the compiler is designed to do everything in one pass: you point it at an ODP and it spits out a freshly-created NSF. This allows it to build up and tear down its environment cleanly, initializing the OSGi plugins for any XPages libraries at the start and doing similarly for any custom classpath jars to be included in the Java runtime.

What supporting incremental compilation would require to be at all speedy and efficient is having a persistent compilation environment. Instead of everything happening sequentially, the IDE would init the compiler process and then send it requests as files need compilation. This has implications for both local and server-based compilation.

Local complication would need to change less: mostly, it would require picking an IPC mechanism and having the launched Equinox process remain alive until it's no longer needed.

Server-based compilation would be similar in implementation, probably using something like HTTP long polling to be able to run in the Domino HTTP container. The trouble would be that a straightforward implementation of this would mean that the Domino server would pretty much have to be dedicated to a single IDE. There's already a potential conflict scenario with two developers doing compilation at the same time: since the XPages compiler needs to install and uninstall OSGi bundles, they could step on each others' toes if any of them overlap. Keeping the compiler environment resident on the server would mean it would have to be effectively locked out to one connection for long periods of time. Assuming HCL continues the Community Edition licensing model, this will be legal to do, but it's still cumbersome.

This could lead into something I've been mulling over: running a Domino compiler server in Docker. This would loosen a lot of the runtime requirements and mean that the encapsulated Domino server would be both dedicated to the purpose and consistent from the perspective of the compiler. Domino's setup requirements initially made it an awkward fit for Docker, but it looks like things have progressed along nicely.

This would all tie perfectly into the Language Server Protocol, which is an IDE-agnostic way to do basically this: have a little running process that knows about the nitty-gritty of the language, and then tell the IDE only what it needs to auto-complete and other features.

Live NSFs

Currently, the compiler starts with an ODP and emits a clean NSF with each build, and this is absolutely, 100% the correct way that it should work. However, Notes being what it is, it'd be expected that a Designer replacement would be able to work with a live NSF, so you could just crack one open, change a view, and be done. The second part of this process is in there, since the compiler uses the normal Notes APIs to store in an NSF as it is. It's the first part that would have to be new, allowing the tooling to selectively look into an NSF.

The exporter already does this, but, like the compiler, goes in one pass. What would potentially make sense would be to do essentially what Designer does: implement a VFS layer to represent an NSF in an equivalent way to the on-disk project. It's more easily said than done, but would be particularly straightforward for Eclipse, for the same reasons that it was straightforward for IBM to do it for Designer.

The secondary question here would be if it would be better to do continue to use DXL as the sole transport mechanism (so editing a view in a live NSF would export it to DXL and then re-import on save) or to instead try to represent things differently. Though DXL is less efficient, particularly for large notes, I think it'd make sense to stick with it - there would be tremendous work involved in trying to make it smarter, and that would be a breeding ground for bugs that just wouldn't exist with DXL.

IDE Features

Getting an NSF to compile dynamically is one thing, but the other part of this kind of project would be making the experience of working with design elements pleasant. In Designer, we have the benefit of having purpose-built editors for each design element type, but these aren't portable even if licensing allowed: the legacy ones all are just wrappers around C++-based "native" UIs, while the newer-era ones are based on Designer's bizarre internal RPC system.

I've done some work along these lines, initially to add autocomplete for custom controls and known core+ExtLib controls to .xsp files. Since that earlier work, I also added a contributor that tells Eclipse to use the DXL schema file for DXL files. While this doesn't give a proper GUI editor, it does provide enough information for Eclipse to pick up on the allowed elements and properties:

While I don't think it'd be worth trying to fully reproduce the various WYSIWYG editors Designer gives you (particularly the view editor, which is laughably bad for data-centric use), I think it'd be worth adding some editors along the lines of my old Forms 'n' Views project. Having some basic editors with a strong focus on the resulting data structure would be perfect for XPages support use and even mostly useful for legacy use.

Time

The core trouble with getting to all these goals, though, is time. For the main compilation and export work, I could justify spending a good amount of time because it eventually more than paid off in less time fighting with Designer to create consistent builds. For this other stuff, though, it's more dependent on whether my hatred for using Designer is enough to tilt the scales. Sometimes, it almost gets there, but I do also need to be able to pay my mortgage, so that puts a bit of a limit on things. It sure would be nice to leave Designer in the dust for good, though.

In this post, I'd like to go over another main component of the NSF ODP Tooling project, the ODP Exporter. The exporter is significantly simpler than the compiler, but still had a surprising number of gotchas of its own.

My goal in writing the exporter was to replace the need to use Designer to create an on-disk project out of an NSF - in one of my projects, in addition to the primary NSF we use, there are also a dozen or so secondary NSFs inheriting from templates and being modified by people not using Git (I know.), and keeping them all in sync is a giant PITA. Previously, I had a dedicated VM just to open the DBs periodically to sync them, but even that took a long time and got error-prone when Designer would miss a change or generally trip over itself.

So I set out to create a compatible replacement, so that I could run a script and update the ODPs en masse.

The Basics

At its core, the exporter does what you might expect: it reads through each design note and sends them through a DXL exporter. For its work, it makes use of the aforementioned design collection and IBM's NAPI. I went with IBM's variant in this case for one class: com.ibm.designer.domino.napi.design.FileAccess. Though this class let me down when it came to importing, it has just enough encapsulated composite-data reader methods to save me a ton of work here, though I had to cheat to access one of them.

For each design note, it determines its type, which contains behavioral information for each type, including whether it should be included in the normal export process at all, where it's placed in the ODP, and the type of export treatment it should get. The main categories of exported note types line up with what the compiler had to know about, with some special knowledge of whether a note is one of many in a folder (e.g. an XPage) or one-per-database (like the icon note).

The Gotchas

Unsurprisingly, things aren't quite as simple as a basic loop. For elements that are just DXL files, it is that easy, but the ones that exist either as just file data (e.g. "plugin.xml") or file data plus metadata require special handling.

Skipped Items

The first thing to note with split data/metadata items isn't complicated, but bears mentioning: the metadata file is generated by exporting the design note as DXL but ignoring data items. Some of these are common among all types, but others (like indexed "$ClassData0", etc. fields) are best matched and excluded with a regex.

LotusScript, Again

LotusScript libraries threw me for an unexpected loop this time. Their storage format is actually not even composite data: the script itself is stored in plain non-summary text items, multiple ones with the same name. However, the NAPI's DXL exporter doesn't actually export the full script test properly, instead only outputting the content of the first item. Additionally, the legacy Java API shows the presence of multiple items with the same name, but also only gives you the value for the first.

So I ended up having to use the raw note format in memory, which DOES include all of the items, and then stitch the script content together onto the filesystem.

Other File Data

The other data types aren't too complicated, but need special cases for each composite data structure, which is where the FileAccess class comes in. Without the convenience methods there, I would have had to write CD iterators to read the data based on the appropriate structures - not terribly difficult, but it's all the better to have the work already done for me. Especially so since FileAccess pleasantly writes directly to a java.io.OutputStream, just like I'd want if I wrote it myself.

Special-Case Files

There are three final special cases that the exporter handles:

1. The icon note is specially-exported not once, but twice. It's exported using an NAPI-specific special method to create the "database.properties" file, which includes the ACL and and formatted settings alongside the icon note, and then also exported specially after the main loop as "Resources/IconNote". I've always appreciated how much Lotus wildly overloaded the icon note.

   • There's also a distinct "$DBIcon" note that houses the 32-bit icon introduced in R8 (if I recall correctly), but that's just a normal old image resource with a special name and not related to the icon note.

2. The "META-INF/MANIFEST.MF" file resource became important in 9.0.1 FP10, but Designer's handling of it is a little schizophrenic. FP10+ will usually fill it in with plugin information when it rebuilds an NSF, but nonetheless exports it as a zero-byte file. It's important for it to exist, so I create a blank file if it doesn't exist.

3. The Eclipse ".project" file is also not present in older NSFs, but is critical for ODPs. If it wasn't exported, I create a generic stub version.

Swiper

When dealing with on-disk projects, Swiper is a mandatory tool, cleaning up the generated XML and (critically) removing extraneous items that change too frequently to be source-control-friendly.

The core of Swiper is an XSLT stylesheet to do the transformation, and I incorporated this wholesale, with a minor modification to retain the ACL that's stripped out by stock Swiper. I then created an OutputStream implementation that passes DXL output through Swiper if configured. As a small note, I think there was a specific reason why I have the Swiper path buffer the DXL into an in-memory ByteArrayOutputStream first instead of just wrapping the file output stream, but I don't remember what that was.

Final Steps

With this post, I think I've covered the big topics I set out to with the two main components of the Tooling. I plan on having at least one final post in the series to cover some potential future additions and enhancements, since I have a lot of ideas in mind for it. Unfortunately, a lot of the most-useful ideas would also be tremendous amounts of work, but the payoff may eventually be worth it.

One of the things that came up frequently when writing both the compiler and exporter portions of the NSF ODP Tooling was rationalizing the multiple ways an NSF is viewed, and determining which aspects are reified in the design notes themselves and which are entirely runtime conjurations.

The Traditional View

To describe what I mean, I'll start with the "traditional" way that design notes work, which is also the mechanism the other views are built upon. The starting point there is the distinction between data and design notes, represented in the API as the note class. For our purposes, there's "data note" and "everything else". The design notes are kept track of internally by what can be considered a magic view, the design collection, which is used implicitly whenever something looks up a design element, and can be accessed automatically by API calls like NIFFindDesignNoteExt.

The design collection itself acts like a normal view, containing columns with pertinent design element information for fast lookups. Beyond the note class value, design notes are distinguished by character-based flags, which you can see in the "Fields" part of the property pane in Designer in the $Flags item. These will look something like "gC~4K" - this value comes from an XPage, and can be interpreted by taking each character and looking for it in "stdnames.h" from the C API:

• g is DESIGN_FLAG_FILE, referring to a "file resource"-type design element (more on this later)
• C apparently matches to DESIGN_FLAG_NO_COMPOSE, used to refer to forms that don't show up in the "Create" menu. I'm not sure why it's included here; it may have some second meaning
• ~ maps to DESIGN_FLAG_HIDEFROMDESIGNLIST, presumably to keep XPages out of standard File Resource pickers
• 4 maps to DESIGN_FLAG_HIDE_FROM_V4, which is reasonable advice, but the fact that this is 4 and not 7 makes me suspect there's a second meaning here too
• K maps to DESIGN_FLAG_XSPPAGE, cheerily documented in the API as "an xpage, much like a file resource, but special!"

The importance of these flags and the reuse of some note classes (file resources in particular) bares a bit of the evolution of the platform. The older the note type is, the more likely it is to have a dedicated note class value. Forms, views, ACLs, and other primordial elements have eponymous classes, but, starting around the web era, new elements started piggybacking on existing classes. This has so far culminated with the XPages-era additions, where almost everything is considered a "file resource", which are themselves already specialized "forms". This mirrors the evolution of file data stored as Composite Data structures, where the first file types added in got their own dedicated structures, later types (like JavaScript libraries) were either crammed awkwardly into similar types or just plopped in as CDFILESEGMENTs (which Domino adorably refers to universally as "CSS").

With the heavy use of flags came something of a mini query language to distinguish collections of design notes. In the API, you can see these in the DFLAGPAT_ C constants. For example, DFLAGPAT_FORM maps to "-FQMUGXWy#i:|@0nK;g~%z^" - the - at the start means that this is a "none of these" matcher, so it's resolved by looking up all notes with NOTE_CLASS_FORM and then filtering out any of the ones with those flags. From our XPage example, you can see it's excluded thrice over, via g, K, and ~. There are other permutations in the language for "match all of", "match any of", and combinations of all three types, and the patterns allow you to select each type of design element you see in Notes and Designer, and a few more categories besides.

Designer's View

Designer really has two views of the NSF. The first view is essentially a codification of what's above, and has been how Notes and Designer have worked forever. When you go to the "Forms" list in Designer, it does a query in the design collection similar to the above form example, and each category of design elements has its equivalent query.

Its second view came along with the Eclipse transition, and it's what you see in Package Explorer. This version takes the core querying capabilities of the design collection and maps it on to an Eclipse File System plugin. From Eclipse-Designer's point of view, the NSF becomes a file-based project as if it was a set of folders and files on the filesystem, but is in reality composed of some dynamic lookups from the design collection paired with a truly local temporary directory for the Local XPages compilation scratch area.

This view of the design became the basis of on-disk project support, with the ODP mirroring what you see in the virtual Eclipse project.

It's also where we start to see a secondary hierarchy within the database design. Traditionally, design notes are largely "flat": while the UI and some APIs have special support for the use of \ within design element names, there's no concept of containers beyond the main categories. For XPages, though, they started to add items like $ClassIndexItem, which contain values like "WEB-INF/classes/frostillicus/controller/ControllingViewHandler.class". These files show up within the "WebContent" folder in the virtual project - "WEB-INF/classes" is by default hidden in Package Explorer, but you can see it in the Navigator view. The use of "WebContent" as a folder for this is itself a holdover from Eclipse-based web app development.

Domino's View

Like Designer, Domino has two views of an NSF and the first is a pretty direct use of the design collection. It has simpler needs, usually just looking up elements by type + flags + name, using reverse view order for web elements.

The second view can be thought of as a stripped-down version of Designer's VFS, but it isn't implemented in the same way and doesn't include all the top-level folders you see in Designer. Instead, Domino uses the aforementioned Java class index items and some other existing values like file-resource names to compose something that resembles a WAR file - you can see this reflected in its use of "WEB-INF/classes". It's this view of the NSF that the XPages runtime container and its many abstraction classes use, allowing them to treat it as an app container in the same way as a normal JEE web app, as if it was just another WAR file. It's not treated fully the same as a WAR file - you can't plop a web.xml file in there and use some other web toolkit - but that's the concept that the XSP stack is going for in classes like com.ibm.domino.xsp.module.nsf.NSFComponentModule.

The On-Disk Project Version

As I mentioned, the ODP is based closely on the Designer view, which in turn is partially based on the "web app" view used for XPages. For the compiler, it's not too big of a deal - it just needs to gather files and import them based on their existing DXL for the most part - but the exporter has to do some fiddly work to shuttle notes to their right spots. By total coincidence, that will be a nice lead-in to my next post, which I expect to cover some details of the ODP exporter portion of the NSF ODP Tooling.

In today's post, I'd like to go over a bit of how the NSF ODP Tooling project is organized, and specifically how I structured it to support both server-based and local compilation.

Setting aside the feature, update site, and distribution modules, the tooling consists of seventeen code-bearing components:

For our purposes today, we care about the first six in the "plugins" directory and then the "nsfodp-maven-plugin" at the bottom - the rest have to do with the different capabilities of the suite.

Commons

The three "commons" plugins contain a set of utilities and data-description classes, and they're broken up into those three modules due to differing dependencies. The core "commons" plugin relies only on org.eclipse.core.runtime, while the "dxl" plugin adds an IBM Commons dependency, and finally the "odp" plugin relies outright on a Notes/Domino runtime. By keeping these things distinct, it lets me keep track of which things are safe to include in the Eclipse UI plugins or the Maven plugin, where I can't count on the present of a Notes runtime.

"Servlet" and "Equinox"

The compiler, like the other "action" components of the Tooling, is split up into the core "compiler" plugin that does the actual heavy lifting, and then two "interface" plugins for running the code from different directions.

The "servlet" plugin came first and is the mechanism by which a local Maven-run plugin communicates with a remote Domino server with the Tooling installed. It contains a primary entrypoint servlet that accepts a packaged zip file from the client containing the ODP and any extra update sites to use while building, as well as a set of HTTP headers describing the various parameters that can be set for compilation. Strictly speaking, this plugin doesn't depend on Domino as such, but rather on having a servlet container and a Notes or Domino runtime - it could hypothetically run in e.g. Tomcat with the right dependencies, but in effect it's the "Domino side" of it.

The "equinox" plugin supports local compilation and it's a bit of an interesting beast. Since the compiler is intended to work with any given NSF and XPages application, it has a hard requirement on the presence of an Equinox ("Eclipse-style") OSGi runtime. A local Maven build doesn't use Equinox, so I wrote this plugin to provide what Equinox refers to as an "application" - essentially a named executable class that can be run once you initialize an Equinox runtime. Eclipse itself uses this mechanism for running, and you can see these in action in the "Eclipse Application" run configuration type in Eclipse-the-IDE:

The code itself behaves similarly to the servlet, but can skip the "zip container" step of the process, instead referencing the local files based on system properties set by the Maven bootstrapper.

Having these two entrypoints lets me keep the actual business of the compiler independent. Depending on need, I could add any number of other entrypoints without having to modify the core code at all.

Maven-side

The actual action of the process is kicked off by a Maven plugin, which consists of what Maven calls a "mojo". It's effectively the same idea as the Equinox application: a specially-tailored executable class. In this case, it gains the ability to specify parameters that are passed in by the pom.xml configuration or via the command line, which are then available by the time the Maven runtime calls the execute() method.

When run, the Maven mojo branches based on what type of compilation it can do. The servlet-based compilation branch is a little wordy in the class, but conceptually simpler than the local compilation. The mojo creates a temporary zip file, pours the ODP into it, and then adds in any update sites to include. Then, it creates an HTTP connection to the remote server, adds headers to configure the compiler, sets the POST body to the zip file, and then lets the server do its thing.

The Equinox runner, though... that's something that took a surprising amount of fiddly magic to get working. On a conceptual level, running the compiler in a local Equinox container is essentially the same thing as the Equinox container launched by the Domino HTTP process - same Eclipse runtime, same infrastructure, and so forth. However, the trouble came in both in some of the fiddly ways that the Domino OSGi runtime is configured and in the assumptions it makes about the active JVM, and the battle resulted in a complicated bootstrapping process. The Notes JVM comes packaged with a handful of critical jar files, not the least of which being "Notes.jar", and those need to be added to the active classpath, which in turn needs a specialized provider plugin to get Equinox to see them. There's also whatever the heck "JEmpower" is, which has its own special needs to be wrapped up into a "shim" OSGi plugin because of the way other plugins depend on it. The runner is also riven with special behavior for running on recent macOS Notes builds, which switched to an embedded non-J9 JVM (I wouldn't be surprised if this changes subtly again in the future). This is all in service of creating a compatible Equinox configuration so that, finally, the compiler can be run in a child process. It's not pretty, but it works.

Progress Messages

Since the process can take a while, I created an extremely-bare-bones messaging system, where the server sends out a series of JSON objects delimited by newlines and the client watches for these and emits human-friendly messages. The compiler process itself just uses an Eclipse-style IProgressMonitor - the servlet uses an implementation called LineDelimitedJsonProgressMonitor, while the local Equinox runner uses one that just prints to the console directly. This is another area where things are kept generic enough at the internal level so that a different mechanism entirely could be hooked in - a GUI progress monitor, for example.

Overall Structure

I'm pretty pleased with how the structure of the Tooling has taken shape. Being able to separate out the entrypoints like this definitely made it much easier to have the local compilation, and breaking it all out into multiple modules kept me from baking in any incorrect assumptions about the runtime environment in the core code. I've been toying with ideas for how to get this stuff to run in an Eclipse/IntelliJ/etc. environment, and I think the Maven Equinox runner will provide a pretty good template for that. There'd be a lot of work to make that good, but it'd definitely be possible.

In the first two posts in this series, I focused on the XPages compilation and runtime environment, independent of anything to do with an NSF specifically. I'll return to the world of OSGi and servlets in later entries, but I'd like to take a bit of time to talk about some specifics of grafting the compiled XPage results and the rest of the on-disk project's contents into an actual NSF.

The Basics

The primary tool that makes an on-disk project work is DXL, the XML representation of a note. DXL defines representations for several kinds of Notes elements, but the three main kinds that you run into with an on-disk project are:

• Database metadata, found in the annotingly-suffixed AppProperties/database.properties file. This contains information from a couple places, in particular the ACL and icon notes

• "Raw" representations of design notes. These show up quite a bit if you select "Use binary DXL" in Designer's preferences, and they show up in a couple parts regardless of that selection. These are distinguished by their use of <note/> as the root element, and contain close to raw data from the NSF. Strings, numbers, and dates are represented in human-readable form, but things like composite data/rich text are stored as Base64-encoded byte arrays matching their in-memory C structures. These "blobs" are opaque to work with but are the safest to round-trip.

  • A subtype of this is the "*.metadata" files, which I'll cover shortly.

• "Encapsulated" design notes, with root elements like <form/> and <view/>. These are friendly to look at and work with programmatically, but the forms in particular run the risk of some edge-case compatibility issues.

The Process

The ODP Compiler uses DXL for almost all of its NSF manipulation, and imports the ODP in a couple of passes based on the different needs of different design elements.

"Direct DXL" Elements

The easiest elements are the ones that are just single DXL files in the ODP and can be imported directly. The compiler iterates over these files as determined by the OnDiskProject class and just passes them in to the DXL importer. Easy peasy.

"Split" Elements

The second main type are resource files that are stored in the ODP as their "normal" file data and paired with a ".metadata" file. The prime example of this are file resources: if you have a file named "foo.txt" stored as a file resource in your NSF, it will exist in the NSF as a normal text file named "foo.txt" and next to it will be a trimmed-down DXL file named "foo.txt.metadata". These metadata files are an export of the "raw" format of the DXL, but then the actual file data items are removed, leaving them contain just the additional items that go along with that (flags, in-NSF file name, etc.).

The conceptual task here is straightforward: encode the file data back into the appropriate composite-data format as Base64 inside the DXL, and then import that. The actual task of doing that, though, gets pretty arcane. There were two ways I could go about it: import the metadata only and then use the C API (via one route or another) to create the structures in memory and append them to the note, or create a C-struct-compatible representation in-memory in Java and add it to the DXL to import. I originally planned on doing the former, as the com.ibm.designer.domino.napi.design.FileAccess class in IBM's NAPI has promisingly-named classes to do this, but I ran into some trouble with some file types that it doesn't support - though file resources, images, script libraries, and others are all conceptually the same thing, the actual C-level storage mechanism for each is slightly different. So I ended up going the latter route, which entailed writing some gnarly code to do it in memory.

XPages Elements

For the most part, XPages and related elements (Custom Controls, themes, Java class files, and Jars) are supersets of file resources: they use the same composite-data structures and store the programmer-visible data in the same $FileData items in the destination notes. Each has an extra layer, though, in order to store the Java bytecode and other info.

Both XPages and Custom Controls share a code path that stores their compiled data into the $ClassData0, $ClassData1, $ClassSize0, and $ClassSize1 items, since they consistently have one class to represent the main page and then a second inner "Page" class to act as an internal component constructor. In addition, Custom Controls store their ".xsp-config" data in $ConfigData and $ConfigSize items in the same note in the NSF.

Java design elements are conceptually similar, but have less predictable class names, and so the code is a little more complex. There's also some special behavior here, in that there are a handful of compiled classes that show up in the compilation result that aren't directly stored in those files. I forget what those are specifically - they might be for secondary, non-public classes that appear at the top level of a Java source file but aren't inner classes.

All of these, in addition to storing their source and class names, also sprout a $ClassIndexItem item that lists the "file paths" for the classes to be used as part of the virtual filesystems that Domino and Designer use when initializing the XPages app.

LotusScript

LotusScript libraries are… special. Though LotusScript embedded in other design notes (forms, views, agents, etc.) doesn't require any special handling beyond importing the DXL, libraries stored as ".lss" files in the on-disk project aren't automatically compiled.

These libraries are brought in with their source stored as normal text items named $ScriptLib, but then need to be compiled from there. There's no mechanism for compiling LotusScript in the normal Java API, and IBM's NAPI doesn't have a binding to the NSFNoteLSCompileExt function involved, so I had to dip into Java C API bindings, initially via Karsten Lehmann's excellent Domino JNA and then switched over to Darwino's NAPI implementation.

If you look at the algorithm I'm using to compile the libraries, you may notice how brute-force it is. Any given library may depend on any given other library, but I don't have a way to know that ahead of time without parsing the code (which I don't want to do). So, in lieu of the kind of dependency graph that Designer creates when you do "Recompile all LotusScript", the ODP Compiler tries each library in turn and, if one fails, it adds it to a "try again" queue. It does this until it's had a chance to effectively try each combination, at which point it will either have a clean queue and can proceed or it'll have one or more libraries that failed to compile for a different reason. It's not pretty, but it gets the job done.

Standalone Elements

There are a handful of components of an ODP that are stored as plain files without associated DXL, generally to do with XPages support files like "xsp.properties". These have some special support in the FileResource class to auto-vivify an associated DXL file on the fly. Fortunately, these files are pretty basic to create, and the only catch was figuring out the appropriate $Flags and $FlagsExt values to fill in. For this, the OnDiskProject class has a set of matchers to match known paths to the specialized file-resource behavior needed for each.

Miscellany

Beyond just importing the ODP files into their right places, the compiler does a few other notable things.

It has the option to populate the $TemplateBuild shared field with template name and build time information, which I've found to be extremely handy. I used to have an agent in a separate DB that would update this in my template DB, and it's much nicer to have the compiler do this automatically. It's also a pleasant fit-and-finish thing.

Similarly, I used to have to remember to take a moment to make sure that the Xsp Properties file in the NTF was set to use compressed and aggregated resources, which was easy to forget. Now, I can have that happen automatically, via filtering during resource import.

Designer exports the "database.properties" file with the current full-text-index status intact, which can actually cause trouble when importing back into a new database. I had to strip that part out if present.

LotusScript compilation relies on the presence of web-service classes in the current Java runtime, which caused trouble when I added local compilation without a Domino server. I guess that this is a knock-on effect, with loading the compiler having the secondary effect of warming the JRE in case you're compiling web services.

Because I forgot that DbDirectory#createDatabase exists (or maybe it was limited, I don't remember), I ended up adding DB creation to Darwino's NAPI, which is a handy capability to have anyway.

Remaining Topics

The more I write about this, the more I find is still left worth covering. In particular, I'd like to go over the architecture of the compiler, how it's architected to run both on a remote server and via a local Equinox OSGi environment. There's also the whole matter of the ODP exporter, which is technically separate but related by workflow and a source of its own bits of arcane knowledge. So much to cover!

 

In yesterday's post, I briefly touched on how the XPages runtime sees its environment by way of a FacesProject and related components. Today, I'd like to expand on that a bit, since it's useful to understand the various layers of what makes up an "XPages app" at compilation and runtimes.

Designer and Domino largely take two paths to try to arrive at the same location in how they view an NSF. The way Designer works is more complicated and opaque than Domino, with extra layers of VFS and an internal RPC mechanism(!) for editors, but there is at least some shared code from the XSP runtime. Beyond that, it does almost the same thing to determine the project's dependency classpath, while the internal NSF classpath is entirely distinct, using Eclipse's project structure to builds towards the different structure Domino will use.

Libraries

The notion of an XSP Library is one of the main parts of directly-shared code between the server and Designer. The way an XSP Library works is that you create a class that implements com.ibm.xsp.library.XspLibrary and then declare that as an IBM Commons extension contribution (more on that later) for the com.ibm.xsp.Library service type.

The fact that this is live code sitting in a plugin has a significant implication. Namely, anything that interprets it has to actually load the class and its dependencies. This is as opposed to just a static configuration file, which could be read without executing any custom code. For the server, the distinction doesn't matter too much, since you'll want to load all your class files anyway. For Designer, this is where we get the requirement to install libraries into Designer itself, rather than just adding plugins to the Target Platform. This is also an area that's a breeding ground for IDE bugs, since Designer needs the plugin available both internally and in the Target Platform, but they're not inherently tied together.

Though the XspLibrary implementation class is executable code, its main purpose is to point the runtime to various bits of static configuration information: the unique identifier for the library (e.g. com.ibm.xsp.extlibx.bazaar.library), lists of *.xsp-config and *-faces-config.xml files to define XSP and JSF contributions, and a list of other library IDs that this one depends on.

I believe that Designer and Domino use these bits of information slightly differently - I'm not sure that Domino cares too much about the *.xsp-config files, for example - but there's a lot of overlap here.

Configuration Files

The two main types of static configuration files used by libraries serve distinct purposes.

The *-faces-config.xml files (not required to be so named, but it's a good convention) are layered under the faces-config.xml file contained in your NSF. They define managed beans, converters, PhaseListeners, and other JSF-isms. These files come directly from the underlying JSF implementation and share the same syntax, at least until the JSF-1.2-era forking of XPages.

The *.xsp-config files look similar - they also use the <faces-config/> root element - but I believe that these are largely an XSP-specific detail. It looks like JSF 1.2 also uses the same <faces-config-extension/> tag, but to a different end - perhaps this evolution started the same way but then diverged there. In any event, these files are where Designer (and the XSP compilation process in general) looks for custom-defined components and their accessible properties. There's an interesting point to note there: though defined components are effectively beans with properties, Designer doesn't introspect the object to get its property names and types, but instead relies entirely on the definitions found in these files. It will still eventually use the component class when it goes to compile the translated XSP Java files, so they still need to be correct, but it's certainly a spot where it's easy to make a typo or mismatched property type.

I think that the latter files aren't used by the server, since their purpose is to provide the XSP source → Java translator with mappings for components' XML elements to the Java classes. However, the core XPages runtime classes on the server still retain knowledge of this configuration, which is how the Bazaar and ODP Compiler do their thing. The com.ibm.xsp.registry package and sub-packages are filled with a mix of parser classes and in-memory representations, like com.ibm.xsp.registry.parse.ConfigParserImpl and com.ibm.xsp.registry.LibraryFragmentImpl.

Non-Library Contributions

Though not related to libraries, it's useful to know about a handful of XPages-specific class contributions that can come into play at runtime. These use the IBM Commons extension mechanism, like libraries themselves, but contribute to a good many different parts of the runtime and application flow. Some of these can be defined inside an NSF, while some are only recognized when defined in plugins - there's a good rundown of these on the ODA wiki. It's pretty rare to see these in the wild, but you may see an application here or there that uses these contributions, via in-NSF files like META-INF/services/com.ibm.xsp.core.events.ApplicationListener.

OSGi and Dependencies

In the early days, XPages was not OSGi-based. That came in in the 8.5.2 era (I believe - I wasn't aware enough in the 8.5.0/8.5.1 era to know the specifics) with the "extensibility API". For the most part, this lineage remains, and the XPages runtime itself isn't too dependent on OSGi, even when it comes to library contributions. Little bits have crept in here and there - the getPluginId() method in XspLibrary and the getOSGiBundle() method in ExtLibLoaderExtension, for example - but it's still largely incidental.

IBM Commons Extensions

If you've done both XPages plugin and Eclipse-the-IDE plugin development, you may have noticed that, while Eclipse plugins usually contribute to customized extension points with complicated schemas, XPages contributions all look like this:

	<extension point="com.ibm.commons.Extension">
		<service type="com.ibm.xsp.Library" class="com.example.SomeXPagesLibrary" />
	</extension>

There are still some places in Domino where you use different extension points, such as when you register a servlet with the Equinox OSGi runtime directly, but for the most part it's just this one point. This is because this extension point is designed to paper over the differences between OSGi extensions and the vanilla-Java-style ClassLoader#getResources mechanism. The type of the service you provide lines up with the META-INF/services/some.extension.type files you can use in your NSF and which still remain inside the embedded jars in the core XPages plugins.

The reason why this OSGi extension point exists is that OSGi intentionally creates separations between the individual plugins that make up your app runtime. In a "normal" web app, all of your dependency jars end up in the WEB-INF/lib sub-directory and are effectively all poured together to make a single class-loading environment. The ClassLoader#getResources route will look through all of the jars in the classpath for these META-INF/services files, but OSGi puts walls between them, and instead provides its own extension mechanism (among others, but this is the one Domino uses).

Dependency Resolution

Both Domino and Designer view the NSF like an OSGi plugin, but go about resolving the dependencies slightly differently. Fortunately, this is a case where the differences seldom crop up in practice - I've only seen some minor differences in how they honor the Export-Package directive in the bundle manifest and how fragment bundles are included.

When Designer is building an XPages app, it references the xsp.properties file to determine which XSP Libraries to include, and then uses their getPluginId() method to determine which OSGi bundle that matches up to (I think). It adds that plugin to the list of dependencies in plugin.xml and (since 9.0.1 FP10) META-INF/MANIFEST.MF. The Eclipse side of Designer then uses that to compose the Plug-in Dependencies list from those bundle IDs and any of their dependencies that are marked as re-exported. I think that Domino only cares about the generated plugin.xml/MANIFEST.MF files - I don't think that it does the resolution based on the library class, though I might be wrong about that.

ODPCompiler's Version

Currently, the ODP Compiler hews closer to the "Domino-style" route. For resolving the active class path, it trusts that the plugin.xml that exists in the ODP is correct and resolves dependencies from there. In the future, it may make sense to have the compiler generate the plugin.xml file itself, in which case it will also have to resolve the plugins based on the library classes. That wouldn't be too difficult, but for now it relies on the exported ODP.

Layer Cake

Looking at the whole XPages architecture, something that strikes me is how much it's simultaneously a giant stack of parts - config parsers, resolvers, runtime bootstrappers, and so forth - but also a pretty straightforward server-side web stack from a Java EE perspective. I've been diving deep into XPages in various ways for a long time now - building complex apps, writing library plugins, and even yanking the runtime out of Domino - yet writing the compiler led to this whole distinct set of capabilities. But a lot of this is essentially "just" ahead-of-time work, with Designer and the ODP Compiler's jobs being a lot of world-resolution followed by placing compiled pieces into the right places in the NSF.

By the time it gets to the NSF, it actually ends up as a pretty normal-style web app - XPages are just Java classes floating around, non-OSGi dependency jars are in WEB-INF/lib, and the faces-config.xml controls rendering in the same way as in JSF. A lot of that, though, will come up in later posts, where I go into the gotchas involved in taking these compilation results and other ODP resources and actually getting them into an NSF.