Note: information on this page refers to Ceylon 1.2, not to the current release.

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Legacy repositories

Ceylon's module system integrates with Maven repositores, and can obtain dependencies (Java jar archives) from a Maven repository via Aether.

Maven repositories

Maven modules are seamlessly supported in the Ceylon module descriptor, but:

  • the module name must be quoted, and
  • the : separator must be used to separate Maven group and artifact ids.

For example:

import "org.hibernate:hibernate-core" "5.0.4.Final";

Maven group and artifact ids

Ceylon uses a single identifier for module names, but Maven uses a group id together with an artifact id. So to import the Maven module with group id org.hibernate and artifact id hibernate-core, we formed a module name by concatenating the two identifiers with a : (colon) and quoting the resulting identifier, resulting in the module name "org.hibernate:hibernate-core" seen above.

Specifying explicit Maven settings

If you have special requirements and need a specific Maven setting.xml, you can specify the file using the rep flag:

ceylon compile --rep aether:/path/to/special/setting.xml com.example.foo

Resolving Maven conflicts

Very often, when working with legacy Maven repositories, we encounter one or all of:

  • versioning conflicts,
  • undeclared dependencies, or
  • the need to export promote transitive dependencies.

These problems arise from the fact that Maven metadata is often only tested with a flat classpath, and breaks when executing on isolated classloaders in Ceylon.

In such scenarios, there are two main ways to proceed:

  • run your Ceylon program on a flat classpath, using the --flat-classpath flag of the command line tools, or
  • use a module overrides file to resolve the problems individually by adjusting the module dependencies.