This section describes most of directories used for Java packaging. Each directory is named in RPM macro form, which shows how it should be used in RPM spec files. Symbolic name is followed by usual macro expansion (i.e. physical directory location in the file system) and short description.

Complex Java applications usually consist of multiple components. Each component can have multiple implementations, called artifacts. Artifacts in Java context are usually JAR files, but can also be WAR files or any other kind of file.

There are multiple incompatible ways of identifying (naming) Java artifacts and each build system often encourages usage of specific naming scheme. This means that Linux distributions also need to allow each artifact to be located using several different identifiers, possible using different schemes. On the other hand it is virtually impossible to every naming scheme, so there are some simplifications.

This chapter describes artifact different ways to identify and locate artifacts in system repository.

RPM has multiple types of metadata to describe dependency relationships between packages. The two basic types are Requires and Provides. Requires denote that a package needs something to be present at runtime to work correctly and the package manager is supposed to ensure that requires are met. A single Requires item can specify a package or a virtual provide. RPM Provides are a way to express that a package provides certain capability that other packages might need. In case of Maven packages, the Provides are used to denote that a package contains certain Maven artifact. They add more flexibility to the dependency management as single package can have any number of provides, and they can be moved across different packages without breaking other packages' requires. Provides are usually generated by automatic tools based on the information from the built binaries or package source.

The Java packaging tooling on Fedora provides automatic Requires and Provides generation for packages built using XMvn. The Provides are based on Maven artifact coordinates of artifacts that were installed by the currently being built. They are generated for each subpackage separately. They follow a general format mvn(groupId:artifactId:extension:classifier:version), where the extension is omitted if its jar and classifier is omitted if empty. Version is present only for compat artifacts, but the trailing colon has to be present unless it is a Jar artifact with no classifier.

The generated Requires are based on dependencies specified in Maven POMs in the project. Only dependencies with scope set to either compile, runtime or not set at all are used for Requires generation. Requires do not rely on package names and instead always use virtual provides that were described above, in exactly the same format, in order to be satisfiable by the already existing provides. For packages consisting of multiple subpackages, Requires are generated separately for each subpackage. Additionally, Requires that point to an artifact in a different subpackage of the same source package are generated with exact versions to prevent version mismatches between artifacts belonging to the same project.

The requires generator also always generates Requires on java-headless and javapackages-tools.

If the package is built built using different tool than Apache Maven, but still ships Maven POM(s), the you will still get automatic provides generation if you install the POM using %mvn_artifact and %mvn_install. The requires generation will also be executed but the outcome largely depends on whether the POM contains accurate dependency insformation. If it contains dependency information, you should double-check that it is correct and up-to-date. Otherwise you need to add Requires tags manually as described in the next section.

For packages without POMs it is necessary to specify Requires tags manually. In order to build the package you needed to specify BuildRequires tags. Your Requires tags will therefore likely be a subset of your BuildRequires, excluding build tools and test only dependencies.

The generated Requires and Provides of built packages can be queried using rpm:

While Requires and Provides generation is automated for Maven projects, BuildRequires still remains a manual task. However, there are tools to simplify it to some extent. XMvn ships a script xmvn-builddep that takes a build.log output from mock and prints Maven-style BuildRequires on artifacts that were actually used during the build. It does not help you to figure out what the BuildRequires are before you actually build it, but it may help you to have a minimal set of BuildRequires that are less likely to break, as they do not rely on transitive dependencies.

Javadoc subpackages in Fedora provide automatically generated API documentation for Java libraries and applications. Java Development Kit comes with tool called javadoc. This tool can be used for generating the documentation from specially formated comments in Java source files. Output of this tool, together with license files, usually represents only content of javadoc subpackages. Note javadoc invocation is typically handled by build system and package maintainer does not need to deal with it directly.

Javadoc subpackage shouldn’t depend on its base package and vice versa. The rationale behind this rule is that documentation can usually be used independently from application / library and therefore base package does not need to be always installed. Users are given an option to install application and documentation separately.