Maven unpack tar.gz artifact of latest version

Question

The goal is to get the latest tar.gz artifact from repository and unpack it to some specific location.

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <version>2.5.1</version>
            <executions>
                <execution>
                    <phase>generate-resources</phase>
                    <goals>
                        <goal>unpack</goal>
                    </goals>
                    <configuration>
                        <artifactItems>
                            <artifactItem>
                                <groupId>com.enterprise</groupId>
                                <artifactId>skrillex</artifactId>
                                <version>${product.version}</version>
                                <type>tar.gz</type>
                                <outputDirectory>target/product</outputDirectory>
                            </artifactItem>
                        </artifactItems>
                    </configuration>
                </execution>
            </executions>
        </plugin>

there is also

<dependencies>
    <dependency>
        <groupId>com.enterprise</groupId>
        <artifactId>skrillex</artifactId>
        <version>${product.version}</version>
        <type>tar.gz</type>
    </dependency>
</dependencies>

but we get the error:

[INFO] --- maven-dependency-plugin:2.5.1:unpack (unpack-unix) @ ... ---
[INFO] Configured Artifact: com.enterprise:skrillex:[1.1.70,):tar.gz
Downloading: https://repo/com/enterprise/skrillex/[1.1.70,)/skrillex-[1.1.70,).tar.gz

...

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-dependency-plugin:2.5.1:unpack (unpack-unix) on project ...: Unable to resolve artifact. Could not transfer artifact com.enterprise:skrillex:tar.gz:[1.1.70,) from/to ext (repo....): IllegalArgumentException

Answer 1

Note: The following is untested, but should work

OK, the issue here is that <artifactItem> does not resolve version ranges.

What you need to do is switch from dependency:unpack to dependency:unpack-dependencies

e.g.

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>2.5.1</version>
        <executions>
            <execution>
                <phase>generate-resources</phase>
                <goals>
                    <goal>unpack-dependencies</goal>
                </goals>
                <configuration>
                    <includeTypes>tar.gz</includeTypes>
                    <includeArtifactIds>skrillex</includeArtifactIds>
                    <outputDirectory>target/product</outputDirectory>
                </configuration>
            </execution>
        </executions>
    </plugin>

(For anyone else following along, you need to add the dependency ensuring you specify the type, e.g.

<dependencies>
    <dependency>
        <groupId>com.enterprise</groupId>
        <artifactId>skrillex</artifactId>
        <version>${product.version}</version>
        <type>tar.gz</type>
    </dependency>
</dependencies>

)

That should ensure that Maven resolves the range, and as the file type is not classpath compatible, the dependency will not be on the transitive classpath of this artifact anyway.

If you were doing this with a classpath compatible dependency, e.g. a .jar dependency, or a dependency that can be treated as such, e.g. a .zip dependency in a .war then you would want to add either <scope>test</scope> or <optional>true</optional> to the dependency so that the transitive dependency tree is not polluted.

Potential issues

There are some things you need to look out for:

• Maven 2.x does not track side-artifact presence in the remote repository, so if the .tar.gz is not attached to every version (or more critically every -SNAPSHOT version) then you can end up with the artifact not being found

• Maven 3.x does track the side-artifact presence in maven-metadata.xml but IIRC only for -SNAPSHOT versions, the idea being that if you deploy "partial" snapshots you can still resolve all the latest side artifacts (even if the latest was for an older -SNAPSHOT towards the same version

• Using version ranges is a really bad plan. It will put a world of pain on downstream consumers of your project as the range gets resolved in accordance with the update settings of your upstream <repositories>. Please reconsider and use a fixed version.

Answer 2

If you don't mind a two step process, use the following pom:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.enterprise</groupId>
<artifactId>skrillex-test</artifactId>
<version>1.0.0-SNAPSHOT</version>
<properties>
    <skrillex.version>[0.0.0,1.0.0)</skrillex.version>
</properties>
<packaging>jar</packaging>
<build>
  <plugins>
    <plugin>
     <groupId>org.codehaus.mojo</groupId>
     <artifactId>versions-maven-plugin</artifactId>
     <version>2.0</version>
     <configuration>
            <includes>
                    <include>com.enterprise:*</include>
            </includes>
     </configuration>
   </plugin>
   <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>2.5.1</version>
        <executions>
            <execution>
                <phase>generate-resources</phase>
                <goals>
                    <goal>unpack</goal>
                </goals>
                <configuration>
                    <artifactItems>
                        <artifactItem>
                            <groupId>com.enterprise</groupId>
                            <artifactId>skrillex</artifactId>
                            <version>${skrillex.version}</version>
                            <type>jar</type>
                            <outputDirectory>target/product</outputDirectory>
                        </artifactItem>
                    </artifactItems>
                </configuration>
            </execution>
        </executions>
    </plugin>
    </plugins>
</build>
<dependencies>
    <dependency>
        <groupId>com.enterprise</groupId>
        <artifactId>skrillex</artifactId>
        <version>${skrillex.version}</version>
    </dependency>
</dependencies>

And run first: mvn versions:resolve-ranges (it updates your pom with the desired version in the property)

followed by the maven goal you want, e.g.: mvn install

Now if you want the original pom back: mvn versions:revert