exists-maven-plugin

Check if a maven artifact exists. Designed around the use case of skipping deployment if the stable version already exists.

How This Plugin Determines if Builds are the "Same"

There are two strategies to determine if a maven artifacts are the "same" as what the project just built: version comparison, and checksum comparison. By default, this plugin uses version comparison. Version comparison simply checks if the group:artifact:version matches an artifact in the local or remote repository. This simple check will not catch the situation where the developer has failed to update the version in pom.xml.

Alternatively, when <cmpChecksum> is true, this plugin compares the checksum of the local or remote artifact with the just built artifact. Checksum comparison requires that the maven build be reproducible. Without specific configuration, maven builds are not reproducible. See Configuring for Reproducible Builds for details on making your build reproducible.

Goals

There are two goals: local checks if the just built artifact is already in the local repository; and remote checks if the just built artifact is already in the remote repository.

Mojo details at plugin info

Parameters

Every parameter can be set with a maven property exists.<parameter_name>. e.g. skip parameter can be set from command line -Dexists.skip=true.

In the following table p: indicates the default constituent properties are prefixed with project. and dm: indicates the default constituent properties are prefixed with project.distributionManagement. e.g. for artifact parameter, the full default is ${project.artifactId}-${project.version}.${project.packaging}

Parameter	Default	Description
artifact	p: ${artifactId}-${version}.${packaging}	The artifact within the project to query
cmpChecksum	false	Compare checksums of artifacts
failIfExists	false	Fail the build if the artifact already exists
failIfNotExists	false	Fail the build if the artifact does not exist
failIfNotMatch	false	Fail the build if the artifact exists and cmpChecksum is set and checksums do not match
lastSnapshotTime		The property to set with the timestamp of the last snapshot install / deploy
project	p: ${groupId}:${artifactId}:${packaging}:${version}	The project within the repository to query
classifier		The classifier to use for checking the repository, e.g. 'tests'
property	${maven.deploy.skip} or ${maven.install.skip}	The property to receive the result of the query
repository	dm: ${repository.url}	For remote goal, the repository to query for artifacts
requireGoal		Execute goal only if requireGoal value matches one of the maven command line goals
serverId	dm: ${repository.id}	For remote goal, the server ID to use for authentication and proxy settings
skip	false	Skip executing the plugin
skipIfSnapshot	true	Skip the query if the project ends with -SNAPSHOT
snapshotRepository	dm: ${snapshotRepository.url}	For remote goal, the repository to query for snapshot artifacts
snapshotServerId	dm: ${snapshotRepository.id}	For remote goal, the server ID to use for snapshot authentication and proxy settings
userProperty	false	If the property should be set as a user property, to be available in child projects

Requirements

• Maven 3.8.1 or later
• Java 11 or later

Typical Use

<build>
  <plugins>

    <plugin>
      <groupId>org.honton.chas</groupId>
      <artifactId>exists-maven-plugin</artifactId>
      <version>0.14.0</version>
      <executions>
        <execution>
          <goals>
            <goal>remote</goal>
          </goals>
        </execution>
      </executions>
    </plugin>

  </plugins>
</build>

Snapshot builds

When checking snapshot builds against a remote/local repository, the last deployed/installed snapshot of the correct version will be matched. Optionally, you can configure a property with the lastSnapshotTime parameter which will receive the build timestamp. If you need additional date math on the timestamp value, open a feature request with your use case.

Preventing failures of remote goal

Consider the scenario where there is an artifact that can only be deployed from a specific build server to a corporate repository with a specialized workflow that ensures various security and license policies. The exists-maven-plugin remote goal is also used to avoid duplicate deployments.

Running maven with the install phase will cause the exists-maven-plugin to execute the remote task. This might fail for various reasons; including the developer laptop is not connected to the internet, or the corporate repository is only available to specific build machines.

We could change the binding of the remote goal to the deploy phase. However, the maven-deploy-plugin's deploy goal will run before exists-maven-plugin's remote goal because "When multiple executions are given that match a particular phase, they are executed in the order specified in the POM, with inherited executions running first."

The solution is to leave the remote goal bound to the install phase and add a requireGoal configuration:

<configuration>
  <!-- run only if deploy goal is specified in maven command line -->
  <requireGoal>deploy</requireGoal>
</configuration>