Nova Ordis Utilities Version Metadata Handling
Internal
Overview
The mechanism relies on a project build pattern and a set of APIs to expose the version and release data of application in a standard manner. The mechanism is used by most of the Nova Ordis projects. clad builds upon it and exposes the version and release metadata as result of the "version" command, which is available by default to all clad-based applications.
The mechanism relies on the presence of a "VERSION" metadata file in the application's classpath. VersionUtilities.getVersion() and VersionUtilities.getReleaseDate() can be used as top-level API to locate, process and display the metadata. In case the metadata file is not found, the both methods log the condition using SLF4J warn() and return null.
In order to insure that the artifacts are built to contain version metadata, follow the instructions provided in the "Build Infrastructure Configuration" section, below.
There is also a "light" version reporting capability, implemented by bash-wrapper-functions, described below ("Light" Version Reporting).
Code
Build Infrastructure Configuration
VERSION File
Place a VERSION file in the src/main/resources directory of the project. It should have the following content -make sure to add a new line after the last line:
version=${version}
release_date=${release_date}
If the project produces a Maven-based complex release artifact, with a "release" module, then place the VERSION file in $PROJECT_HOME/release/src/main/resources.
If the project was initialized with nort, this should have been done automatically already. For more details see "New Project Initialization with nort".
Custom Resource File
If multiple JAR artifacts present on the same classpath use the same versioning mechanism, there will be collisions, so in this case is best to use an artifact-specific version file name, instead of the generic VERSION.
VersionUtilities support using custom version files instead of the "VERSION" default, by exposing the get...(String fileName) methods.
${version} and ${release_date} in the In-Line Documentation of the Project
Since we are going to use the Maven resource plugin to filter resources and replace variables, you can also use ${version} and ${release_date} in the in-line documentation, for example the main USAGE file. Example:
myApp version ${version} released on ${release_date}
...
Define maven.build.timestamp.format and release_date
Make sure the top-level POM file of your project contains the definition of the build timestamp format and release_date, as follows:
...
<properties>
<maven.build.timestamp.format>MM/dd/yy</maven.build.timestamp.format>
<release_date>${maven.build.timestamp}</release_date>
</properties>
...
The "version" property is available by default.
Enable Variable Substitution
The variable substitution can be enabled in two different way, depending on how the final artifact is being built. If the default artifact building mechanism is in effect, the variable substitution will be performed by the Maven resource plugin, as described in the "Configure the Maven Resources Plugin" section. If the project produces a Maven-based complex release artifact, with a "release" module, the variable substitution will be performed by the assembly plugin and it can be configured as described in the "Configure Assembly Variable Substitution" section.
Configure the Maven Resources Plugin
Make sure the Maven Resources Plugin is available and configured as described here: variable substitution in resource files.
Essentially, we want:
<filtering>true</filtering>
Configure Assembly Variable Substitution
Add the following section to the assembly descriptor:
<assembly ...>
...
<files>
...
<file>
<source>./src/main/resources/VERSION</source>
<outputDirectory>lib</outputDirectory>
<filtered>true</filtered>
</file>
...
</files>
</assembly>
More details on assembly filtering configuration are available in here: "Assembly Filtering and System Property Substitution".
Usage
When all of the above are completed, the final artifact should contain correctly resolved ${version} and ${release_date} in all resources that have been filtered.
To get the version and release date programmatically, use the following API.
The utility code can be used as part of clad or directly.
Example:
String version = VersionUtilities.getVersion();
String releaseDate = VersionUtilities.getReleaseDate();
System.out.println("version " + version);
System.out.println("release date " + releaseDate);
"Light" Version Reporting
The "light" version reporting capability is implemented by bash-wrapper-functions. It consists in a get-version() bash function that attempts to locate the VERSION file. If found, the information contained by the filed is displayed, and the "version" command is handled at the shell level, and not passed to the Java runtime. If the file is not found, the command is passed to the Java runtime.
See:
Light version reporting is only appropriate for a command line utility that executes quickly and exit. For long running processes, where the version of the code that is executing may potentially be different than the version of the code on the disk, immediately after an upgrade, this mechanism is not recommended.