An attempt to add some sanity to maven dependencies across multiple gradle projects
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gdmc @ a124884

gdmc: Gradle Dependency Management Center

A gradle plugin that aims to simplify gradle files by refactoring version definitions into a separate (and sharable) json file, while also providing a number of tasks to automate the resolution of new and upgradable dependencies.

See our project goals for more.


Add gdmc to your buildscript dependencies...

buildscript {
  repositories { maven { url "" } }
  dependencies {
    classpath 'com.episode6.hackit.gdmc:gdmc:0.1.9'

In your project's build.gradle, apply the gdmc plugin and define your dependencies without versions

apply plugin: 'java'
apply plugin: 'com.episode6.hackit.gdmc'

dependencies {

  // Leave versions out of your dependency declarations
  compile 'net.sourceforge.findbugs:jsr305'
  compile 'com.episode6.hackit.chop:chop-core'

  // you can also use the map format without a version
  testCompile group: 'junit', name: 'junit'

Before your first build, execute the gdmcResolve task. A gdmc.json file will be automatically generated for you.

    "com.episode6.hackit.chop:chop-core": {
        "groupId": "com.episode6.hackit.chop",
        "artifactId": "chop-core",
        "version": "0.1.8"
    "junit:junit": {
        "groupId": "junit",
        "artifactId": "junit",
        "version": "4.12"
    "net.sourceforge.findbugs:jsr305": {
        "groupId": "net.sourceforge.findbugs",
        "artifactId": "jsr305",
        "version": "1.3.7"

This file should be added to your project's source control, once it has been generated you should be able to build normally and the versions mapped in the gdmc.json file will be applied.

Importing existing dependencies

If you're adding gdmc to an existing project with many dependencies, you can, instead, execute the gdmcImport task before removing the versions from your build.gradle. This will import the fully-qualified dependencies from your project into the gdmc.json file instead of resolving their latest versions.

gdmc file

gdmc will look for it's json file in the following locations in the following order

  • If the gradle property gdmc.file contains a valid file path, it will be used.
  • $rootDir/gdmc.json will be used if it exists
  • $rootDir/gdmc/gdmc.json will be used if it exists.

If no valid gdmc file is found, $rootDir/gdmc.json will be used.

gdmc tasks

gdmc provides the following tasks to handle resolving, importing and upgrading dependencies.

  • gdmcResolve: Find any unmapped dependencies in the project (i.e. version not defined in gradle, and key not mapped in gdmc), resolve the latest release version of said dependencies, and add them to gdmc.json
  • Note: some plugins cause dependencies to be resolved before this task gets a chance to execute (android gradle build tools is a known example). If you see an unmapped dependency error when executing this task, simply override the gdmc.forceResolve gradle property by running
./gradlew -Pgdmc.forceResolve=true gdmcResolve
  • gdmcImport: Find fully-qualified dependencies in the project (i.e. versions are defined in-line in build.gradle) and add those explicit versions to gdmc.json
  • To overwrite existing entries in gdmc.json, override the gdmc.overwrite gradle property by running
./gradlew -Pgdmc.overwrite gdmcImport
  • gdmcImportBuildscript: Like gdmcImport, but imports dependencies defined in your buildscript block. While gdmc can't manage these buildscript dependencies for you, we do validate them in the gdmcValidateBuildscriptDeps task.
  • gdmcImportTransitive: Same as gdmcImport except it will also import all transitive dependencies to your gdmc.json
  • gdmcUpgrade: Find all properly mapped gdmc dependencies in your project, and resolve the latest release versions of each of them. Then dump those new versions into gdmc.json, overwriting whatever was there.
  • gdmcUpgradeBuildscript: Like gdmcUpgrade, but upgrades gdmc's references to dependencies defined in your buildscript block.
  • gdmcUpgradeAll: Upgrade all entries in your gdmc.json file, regardless of if they're defined in you project.
  • gdmcValidateSelf: A validation task that gets added as a dependant task to check for projects that are meant to be deployed. It ensures that the current version of your project is referenced in your gdmc.json file (assuming it's not a snapshot).
    • You should only need gdmc self validation if sharing a single gdmc file with multiple projects/repos. If you don't need this validation it can be disabled with...
gdmcValidateSelf.required = {false}
  • gdmcImportSelf: Add/update an entry in gdmc.json for this project using the group, name, and version defined in gradle. Run this task if gdmcValidateSelf is failing.
  • gdmcValidateBuildscriptDeps: A validation task that gets added as a dependant task to check and test. Looks to see if any of your buildscript dependencies are mapped in gdmc, and fails the build if the versions being used are different from those referenced in gdmc.

gdmc aliases

If you want to define groups of dependencies or even just shorten some dependency names, you can manually add aliases to the gdmc.json file.

  • namespaced aliases contain a ':' (colon)
    "e6:chop-core": {
        "alias": ["com.episode6.hackit.chop:chop-core"]
    "e6:chop-android": {
        "alias": ["com.episode6.hackit.chop:chop-android"]
  • raw aliases do not contain a ':' (colon)
    "chop-all": {
        "alias": [
  • In your build.gradle, you can then reference the shorter aliases
dependencies {
  // namespace aliases can be referenced directly
  compile 'e6:chop-core'

  // raw aliases must be wrapped by the gdmc method for gradle to handle them properly
  compile gdmc('chop-all')

gdmc locked dependencies

If needed, you can lock gdmc dependencies to a specific version by adding "locked": true to the entry in gdmc.json. This will force gdmc's tasks to ignore it when upgrading/importing dependencies.

    "javax.inject:javax.inject": {
        "groupId": "javax.inject",
        "artifactId": "javax.inject",
        "version": "1",
        "locked": true

reading versions directly

It's also possible to read a version directly using the convention method gdmcVersion(key). For example, in a multi-module android app you could add the following sparse version definitions to your gdmc.json file

    "android.compilesdk": {
        "version": "25",
        "locked": true
    "android.buildtools": {
        "version": "26.0.0",
        "locked": true

(Notice these sparse dependencies must be locked otherwise the gdmcUpgrade* tasks will all fail)

Then you can reference the versions in your modules' build.gradle files and gdmc becomes your single source of truth...

android {
    compileSdkVersion gdmcVersion('android.compilesdk') as Integer
    buildToolsVersion gdmcVersion('android.buildtools')

version inheritance

If you work with multi-module dependencies, they can share a single version via version inheritance.

    "com.episode6.hackit.chop:chop-core": {
        "groupId": "com.episode6.hackit.chop",
        "artifactId": "chop-core",
        "version": "0.1.9"
    "com.episode6.hackit.chop:chop-android": {
        "groupId": "com.episode6.hackit.chop",
        "artifactId": "chop-android",
        "inheritVersion": "com.episode6.hackit.chop:chop-core"
    "com.episode6.hackit.chop:chop-junit": {
        "groupId": "com.episode6.hackit.chop",
        "artifactId": "chop-junit",
        "inheritVersion": "com.episode6.hackit.chop:chop-core"

gdmc and spring dependency management plugin

Gdmc can be used as along-side Spring's dependency management plugin. This allows you to combine gdmc mappings with mavenBoms, and enables enforced versions for transitive dependencies (something gdmc does not handle on its own).

Instead of applying the normal gdmc plugin, apply the gdmc-spring-compat plugin along-side io.spring.dependency-management...

buildscript {
  repositories {
  dependencies {
    classpath 'io.spring.gradle:dependency-management-plugin:1.0.0.RELEASE'
    classpath 'com.episode6.hackit.gdmc:gdmc:0.1'

apply plugin: 'io.spring.dependency-management'
apply plugin: 'com.episode6.hackit.gdmc-spring-compat'

In this mode gdmc will dump it's dependency map into spring's dependencyManager, and most of the mapping will be handled by the spring plugin (aliases are still mapped by gdmc, as they are not supported by dependencyManager). You can add to or override gdmc's mapping (and add exclude blocks) via the usual dependencyManagement DSL

gdmc override files

Gdmc can apply overrides to its dependency map / main gdmc file. These overrides will only take effect when resolving builds and are ignored during import/resolve/upgrade tasks. This can be helpful if you share a single gdmc file with other projects via submodule, but need to apply some custom groups or versions to your module. To apply, set the gdmc.overrideFiles property in your file...


# Apply gdmc override files. Order matters, the last file
# listed will overwrite the first if they contain the same mappings

Gdmc override files look just like gdmc json files and support all the same features except for locked.

gdmc goals

  • Allow dependencies to be decalred in gradle without versions defined
  • If you've used Spring's dependency management plugin, this will sound familiar. The dependency management plugin & gdmc do share some functionality, but have different areas of focus (gdmc doesn't override transitive dependencies or handle mapped exclusions at this time). You can actually use gdmc along-side spring's dependency management plugin by applying the com.episode6.hackit.gdmc-spring-compat plugin instead of the normal gdmc plugin.
  • Map dependency keys -> versions in a separate file, and make it possible for that file to be stored in a submodule, so that it may be shared by multiple projects.
    • Technically, the spring dependency management plugin can also accomplish this by defining your dependencyManagement{} block in a separate file, and applying that file to your project. This is a valid alternative if have no use for the requirements below.
    • The spring plugin also has a mechanism for 'releasing' mavenBoms (groups of dependencies) to public maven repos, but this adds an entire new release cycle just for managing versions and feels like too much process. In the case of our small, new and volitile libraries, the instant updates and branching capabilities of a submodule are more appealing.
  • Automatically resolve missing dependencies via a gradle task so that you don't have to explicitly look up current versions (without a good reason).
    • Since we want to update the map programmatically, we decided to back it with a (pretty-printed) json file instead of a groovy file.
  • Provide gradle tasks to upgrade dependencies that are mapped via gdmc, to make it easier to stay on the latest stable releases or your dependencies
  • Provide a mechanism to define aliases for dependencies with long or obnoxious groupIds, and for groups of dependencies that often get applied together.