Managing Maven / JAR Dependencies

This skill explains how to add, update, and remove Maven/JAR dependencies in a Mendix module using MDL. These are the dependencies declared in Studio Pro's Module Settings → Java dependencies tab, stored as Projects$JarDependency entries inside the module's Projects$ModuleSettings unit.

When to Use This Skill

• Adding a new external library for a Java action (Jackson, Apache HTTP client, etc.)
• Updating a library version across modules
• Disabling a dependency without removing it (included = false)
• Auditing which modules have JAR dependencies

If you only need to copy JARs into vendorlib/ for a local build (without registering them in module settings), that is a different operation and does NOT require MDL.

Listing Dependencies

-- All modules
LIST JAR DEPENDENCIES;

-- Single module
LIST JAR DEPENDENCIES IN MyModule;

Output columns: module, group, artifact, version, included.

Describing a Dependency

DESCRIBE JAR DEPENDENCY MyModule 'com.fasterxml.jackson.core:jackson-databind';

Outputs a re-executable ALTER MODULE ... ADD JAR DEPENDENCY (...) block.

Adding a Dependency

ALTER MODULE MyModule
  ADD JAR DEPENDENCY (
    group    = 'com.fasterxml.jackson.core',
    artifact = 'jackson-databind',
    version  = '2.21.2',
    included = true,
  );

• included defaults to true when set explicitly; always set it to be explicit.
• The coordinate group:artifact must be unique within the module.

Updating a Dependency

-- Change the version
ALTER MODULE MyModule
  SET JAR DEPENDENCY 'com.fasterxml.jackson.core:jackson-databind' VERSION '2.21.3';

-- Disable without removing (keeps the entry, classpath excluded at build time)
ALTER MODULE MyModule
  SET JAR DEPENDENCY 'com.fasterxml.jackson.core:jackson-databind' INCLUDED false;

Managing Transitive Exclusions

-- Exclude a transitive dependency
ALTER MODULE MyModule
  SET JAR DEPENDENCY 'org.duckdb:duckdb_jdbc'
    ADD EXCLUSION 'com.example:conflicting-lib';

-- Remove an exclusion
ALTER MODULE MyModule
  SET JAR DEPENDENCY 'org.duckdb:duckdb_jdbc'
    DROP EXCLUSION 'com.example:conflicting-lib';

Removing a Dependency

ALTER MODULE MyModule
  DROP JAR DEPENDENCY 'com.fasterxml.jackson.core:jackson-databind';

Jackson Version Gotcha

Jackson 2.x and 3.x use different package namespaces:

Version	Group ID	Import prefix
2.x	com.fasterxml.jackson.core	com.fasterxml.jackson.*
3.x	tools.jackson.core	tools.jackson.*

If Java code imports com.fasterxml.jackson.databind.* you need 2.x. Pin to the version the Mendix runtime bundles to avoid classloader conflicts:

ls ~/.mxcli/mxbuild/<runtime-version>/runtime/bundles/ | grep jackson

After Adding a Dependency

MDL writes the Projects$JarDependency entry into the .mpr file. Gradle still needs to resolve and download the JAR:

1. Open the project in Studio Pro — it will trigger Gradle to populate vendorlib/.
2. Or run mxcli docker build which invokes mx and triggers the Gradle sync.

Until Gradle runs, the JAR is declared but not yet present in vendorlib/. This is the same state as adding a dependency in Studio Pro before clicking OK.

Coordinate Format

Coordinates use the group:artifact format (no version):

'com.fasterxml.jackson.core:jackson-databind'
'org.duckdb:duckdb_jdbc'

The version is stored separately and shown in LIST JAR DEPENDENCIES output.

Related Skills

• java-actions — authoring Java actions
• project-settings — other module/project settings