Q:

Working with ceylon import-jar

How can I import a library from maven central into a project with the ceylon import-jar command?
Please show the full command. 
E.g. for "joda-time-2.9.4.jar" from "http://repo.maven.apache.org/maven2/" into a local directory.
I guess it must be:
./ceylon-1.2.3/bin/ceylon import-jar --rep  "http://repo.maven.apache.org/maven2/" --verbose --out localdir "joda-time:joda-time/2.9.4" "joda-time-2.9.4.jar"

But as far as I can see the tool is not working (ceylon versions 1.2.2 and 1.2.3).
Working with maven central is essential.
This question is linked with The ceylon copy tool because both tools present me with a riddle.

A:

I understand you are asking about the ceylon import-jar tool specifically, but would like to offer a different solution that is easier if your goal is to import a jar from a remote repository.
I would suggest you use the Ceylon Gradle Plugin, which I wrote.
It knows how to grab dependencies from repositories (including JCenter and Maven Central, but many others), and it will run the ceylon -import-jar tool for you automatically.
Full Example:

Run the following command to create a new test project (enter simple for the folder name):

ceylon new simple --module-name=com.athaydes.test --module-version=1.0

Enter the new project name and have a look at what's in it (minimum Ceylon project):

cd simple
tree # or use Finder, Window Explorer or whatever
You'll see this:

    └── source
        └── com
            └── athaydes
                └── test
                    ├── module.ceylon
                    ├── package.ceylon
                    └── run.ceylon

Edit module.ceylon so it has the following contents (add whatever dependencies you want):

    module com.athaydes.test "1.0" {
      native("jvm")
      import joda_time.joda_time "2.9.4";
    }

Notice the name of the module must be a valid Ceylon identifier! So, the Gradle plugin replaces invalid characters with _, generating a valid Ceylon identifier from the Maven artifact name.

Create a build.gradle file at the root of the project so the Gradle plugin can work, with the following contents:

    plugins {
        id "com.athaydes.ceylon" version "1.2.0"
    }

    repositories {
        jcenter()
    }

    ceylon {
        module = "com.athaydes.test"
        flatClasspath = false
        importJars = true
        forceImports = true // necessary to bypass optional dependencies issues in Maven poms
    }

    dependencies {
        ceylonCompile "joda-time:joda-time:2.9.4"
    }

We must declare this dependency here as a normal Maven dependency so Gradle knows where to get the Jars from.

Done... now just run importJars:

gradle importJars
Or, to just see the actual command generated (will not actually run it):
gradle -P get-ceylon-command importJars

Here's the generated command:
ceylon import-jar   
  --force  
  --descriptor=/Users/renato/programming/experiments/ceylon-gradle/simple/build/module-descriptors/joda_time_2.9.4.properties  
  --out=/Users/renato/programming/experiments/ceylon-gradle/simple/modules  
  --rep=aether:/Users/renato/programming/experiments/ceylon-gradle/simple/build/maven-settings.xml 
  --rep=/Users/renato/programming/experiments/ceylon-gradle/simple/modules
  joda_time.joda_time/2.9.4
  /Users/renato/.gradle/caches/modules-2/files-2.1/joda-time/joda-time/2.9.4/1c295b462f16702ebe720bbb08f62e1ba80da41b/joda-time-2.9.4.jar

The jars will be imported to the default location, modules (but you can configure that):

── build
│   ├── dependency-poms
│   │   └── joda-time-2.9.4.pom
│   ├── maven-repository
│   │   └── joda-time
│   │       └── joda-time
│   │           └── 2.9.4
│   │               ├── joda-time-2.9.4.jar
│   │               └── joda-time-2.9.4.pom
│   ├── maven-settings.xml
│   └── module-descriptors
│       └── joda_time_2.9.4.properties
├── build.gradle
├── modules
│   └── joda_time
│       └── joda_time
│           └── 2.9.4
│               ├── joda_time.joda_time-2.9.4.jar
│               ├── joda_time.joda_time-2.9.4.jar.sha1
│               └── module.properties
└── source
    └── com
        └── athaydes
            └── test
                ├── module.ceylon
                ├── package.ceylon
                └── run.ceylon

Now you can run the Ceylon code with the runCeylon task (or just run if there's no other task with this name):
gradle run

NOTE:
Unfortunately, actually importing the specific Jar you chose into the Ceylon repo is impossible with its original name... because in Ceylon, joda-time is an illegal identifier... so you need to change the name of the module when imported by Ceylon. The Gradle plugin does it for you.. but you need to know what the valid identifier will be to be able to write the import statement in the module file (you can just let the plugin run and it will tell you what the name will be).

A much simpler approach
If you want to avoid the complexity of this approach, you can just use the default Gradle plugin approach to NOT import Maven jars into the Ceylon repository and just use the simple Java classpath (which means you relinquish using the Ceylon modules system!).
If you do that, your build.gradle file will look like this:
plugins {
    id "com.athaydes.ceylon" version "1.2.0"
}

repositories {
    jcenter()
}

ceylon {
    module = "com.athaydes.test"
}

And the module.ceylon file:
module com.athaydes.test "1.0" {
  native("jvm")
  import "joda-time:joda-time" "2.9.4";
}

Notice that we don't need to mess up with the dependency name using this approach. From Ceylon 1.2.3, you should prepend the dependency with the maven: qualifier to avoid warnings.

That simple!

