Configuration

This page explains how the goal is wired (variables, metadata, formats) and how the pieces fit together. The authoritative, per-parameter documentation is the generated render goal reference .

Variables

Before any diagram is loaded, the goal builds a Hop variable space and injects values into it:

the Maven project properties are added first,
then the variables from the config file (if any).

The default config file is a standard Hop project-config.json; the goal reads its config.variables array, where each entry is {name, value, description}. A file exposing a top-level variables array (same entry shape) is also accepted, which is convenient for environment config files.

These variables resolve HOP references such as ${pc.databases.ora11.host} or ${pc.sync.audit.table}. References that remain unresolved are rendered verbatim (for example ${PROJECT_HOME}) without failing the build.

TIP	the sample project stores connection settings in an `env-config.json` with a `variables` array; that file is directly usable as the `configFile`.

Metadata

The metadataFolder (default <project-basedir>/metadata) is handed to a JsonMetadataProvider wrapped in a MultiMetadataProvider. This lets rdbms connections and other metadata referenced by the pipelines resolve during loading. Without it, files referencing shared metadata could fail to load.

Formats

The formats parameter selects which diagrams to write. Each format produces one file per source diagram, and the exporter is chosen with a switch on the format plus the subject type (pipeline or workflow):

SVG - Scalable Vector Graphics (.svg)
MERMAID - Mermaid flowchart (.mmd)

The output uses the source-relative path prefixed by targetFolder, so multiple formats coexist without overwriting each other.

Output folder

targetFolder defaults to ${project.build.directory}/hop-diagrams. It is created if needed and the source-relative directories are mirrored under it.

Notes and magnification

includeNotes controls whether Hop notepad annotations are included in the diagram, and magnification scales the SVG output (default 1.0).

Auto-resolving Hop plugins

Out of the box Hop discovers the transforms and actions shipped by the hop-transform-* and hop-action-* modules that are on the plugin classpath: without them the icons are rendered as a generic box (or the build fails with failOnMissing).

Set autoResolve to true to let the goal resolve the missing modules with the Maven resolver:

<configuration>
  <autoResolve>true</autoResolve>
</configuration>

The goal scans the rendered .hpl/.hwf files, extracts the transform and action ids, maps every id to an artifact and resolves it (with its transitive dependencies) into <target>/hop-plugins/transforms/<artifactId>/ (or actions/), then registers the plugins into the Hop registry programmatically. No JVM-global system property is set, so several goal executions can run concurrently in the same build: the resolution and staging phase is lock-free, only the registry registration is serialized on the Hop environment class.

The resolutions are run in parallel with Maven's own artifact-thread setting: the number of workers comes from the same maven.artifact.threads configuration the resolver uses (falling back to aether.dependencyCollector.bf.threads
, then 1). The staging copies are idempotent (temp file + atomic move), so repeated or concurrent executions never observe partial files.

The plugin compiles against the Maven Resolver 1.9.x API but keeps its jars provided: it runs against whatever resolver Maven ships - 1.9.x on Maven 3.9, 2.x on Maven 3.10 and Maven 4 - using only the API that is stable and non-deprecated on both majors.

id to artifact mapping

The default rule is org.apache.hop:hop-transform-<id> / org.apache.hop:hop-action-<id> (lowercase), completed by a built-in table for the modules that bundle several plugins (for example CsvInput, TextFileInput2 and TextFileOutput all live in hop-transform-textfile). Override or extend it per plug-in id:

<configuration>
  <autoResolve>true</autoResolve>
  <transform2ArtifactMapping>
    <DataGrid>org.apache.hop:hop-transform-datagrid:2.20.0</DataGrid>
  </transform2ArtifactMapping>
  <action2ArtifactMapping>
    <WRITE_TO_LOG>com.acme:custom-write-to-log</WRITE_TO_LOG>
  </action2ArtifactMapping>
</configuration>

Each value is either a bare artifactId (resolved with the detected Hop version), a groupId:artifactId pair, or full groupId:artifactId:version coordinates.

Parameters

autoResolve - enable the resolution (default false)
transform2ArtifactMapping / action2ArtifactMapping - id to artifact overrides (see above)
autoResolvePluginsFolder - staging folder, default ${project.build.directory}/hop-plugins
autoResolveVersion - version used for bare artifactIds, defaults to the Hop version the plugin runs against

TIP	the staged folder is a plain cache: it can be deleted, the artifacts are re-resolved on the next run from the local Maven repository.

Example: non-standard layout

<configuration>
  <sourceFolder>${project.basedir}/src/main/repositories</sourceFolder>
  <metadataFolder>${project.basedir}/src/main/repositories/metadata</metadataFolder>
  <configFile>${project.basedir}/src/main/resources/hosts/local/env-config.json</configFile>
  <targetFolder>${project.build.directory}/hop-diagrams</targetFolder>
  <formats>
    <format>SVG</format>
  </formats>
</configuration>

Next steps

Review the generated goals index and the render goal reference for the exact parameter names, types, required flags, defaults and Maven properties.

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