How the ODP Compiler Works, Part 3

Jul 2, 2019, 11:26 AM

Tags: nsfodp
  1. Next Project: ODP Compiler
  2. NSF ODP Tooling 1.0
  3. NSF ODP Tooling Example Project
  4. NSF ODP Tooling 1.2
  5. How the ODP Compiler Works, Part 1
  6. How the ODP Compiler Works, Part 2
  7. How the ODP Compiler Works, Part 3
  8. How the ODP Compiler Works, Part 4
  9. How the ODP Compiler Works, Part 5
  10. How the ODP Compiler Works, Part 6
  11. How the ODP Compiler Works, Part 7

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/ 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 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 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 "". 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.


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 "" 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!


Commenter Photo

Paul Withers - Jul 3, 2019, 11:55 AM

Similarly, I created a createDatabase method in ODA, copying a blank NSF file from ODA into the file system. Then Nathan told me about that DbDirectory method and ODA now uses that.

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