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util-repositories.md

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Repositories

Many components need to have access to multiple versions of binaries. The buildpack provides a Repository abstraction to encapsulate version resolution and download URI creation.

Repository Structure

The repository is an HTTP-accessible collection of files. The repository root must contain an index.yml file that is a mapping of concrete versions to absolute URIs consisting of a series of lines of the form:

<version>: 
    uri: <URI of binary>
    license: <URI of license>

The collection of files may be stored alongside the index file or elsewhere.

An example filesystem might look like:

/index.yml
/ibm-java-jre-7.0-5.0-x86_64-archive.bin
/ibm-java-jre-7.0-5.0-x86_64-License.html

Usage

The main class used when dealing with a repository is LibertyBuildpack::Repository::ConfiguredItem. It provides a single method that is used to resolve a specific version to the URI containing the binary as well as a URI containing the License.

# Finds an instance of the file based on the configuration.
#
# @param [Hash] configuration the configuration
# @option configuration [String] :repository_root the root directory of the repository
# @option configuration [String] :version the version of the file to resolve
# @param [Block, nil] version_validator an optional version validation block
# @return [LibertyBuildpack::Util::TokenizedVersion] the chosen version of the file
# @return [String] the URI and License URI of the chosen version of the file
def self.find_item(configuration, &version_validator)

Usage of the class might look like the following:

version, uri = LibertyBuildpack::Repository::ConfiguredItem.find_item(configuration)

or with version validation:

version, uri = LibertyBuildpack::Repository::ConfiguredItem.find_item(configuration) do |version|
  validate_version version
end

Version Syntax and Ordering

Versions are composed of major, minor, micro, and optional qualifier parts (<major>.<minor>.<micro>[_<qualifier>]). The major, minor, and micro parts must be numeric. The qualifier part is composed of letters, digits, and hyphens. The lexical ordering of the qualifier is:

  1. hyphen
  2. lowercase letters
  3. uppercase letters
  4. digits

Version Wildcards

In addition to declaring a specific versions to use, you can also specify a bounded range of versions to use. Appending the + symbol to a version prefix chooses the latest version that begins with the prefix.

Example Description
1.+ Selects the greatest available version less than 2.0.0.
1.7.+ Selects the greatest available version less than 1.8.0.
1.7.0_+ Selects the greatest available version less than 1.7.1. Use this syntax to stay up to date with the latest security releases in a particular version.