Dependency Tree Output Formats

The dependency:tree goal of the Maven Dependency Plugin generates a representation of a project's dependency tree. The outputType parameter allows you to specify the output format, which can be written to a file using the outputFile parameter or printed to the console. Supported formats are json, dot, graphml, and tgf. This section describes each format, its structure, and example usage.

mvn dependency:tree -DoutputType=<format> -DoutputFile=<filename>

JSON (outputType=json)

Description: The JSON format represents the dependency tree as a hierarchical JSON object. The root node describes the project's artifact, and its dependencies are listed in a children array, with nested dependencies recursively included.

Structure:

• Root Node:
  • groupId: The group ID of the project or dependency (e.g., org.apache.maven.extensions).
  • artifactId: The artifact ID (e.g., maven-build-cache-extension).
  • version: The version (e.g., 1.2.1-SNAPSHOT).
  • type: The artifact type (e.g., jar).
  • scope: The dependency scope (e.g., compile, test, or empty for the project itself).
  • classifier: The classifier, if any (e.g., empty string if none).
  • optional: Whether the dependency is optional (true or false).
  • children: An array of dependency objects with the same structure, representing transitive dependencies.
• Nested Dependencies: Each dependency in the children array follows the same structure, allowing for recursive representation of the dependency tree.

Example:

{
  "groupId": "org.apache.maven.extensions",
  "artifactId": "maven-build-cache-extension",
  "version": "1.2.1-SNAPSHOT",
  "type": "jar",
  "scope": "",
  "classifier": "",
  "optional": "false",
  "children": [
    {
      "groupId": "net.openhft",
      "artifactId": "zero-allocation-hashing",
      "version": "0.27ea0",
      "type": "jar",
      "scope": "compile",
      "classifier": "",
      "optional": "false"
    },
    {
      "groupId": "org.apache.maven.wagon",
      "artifactId": "wagon-webdav-jackrabbit",
      "version": "3.5.3",
      "type": "jar",
      "scope": "compile",
      "classifier": "",
      "optional": "false",
      "children": [
        {
          "groupId": "org.apache.jackrabbit",
          "artifactId": "jackrabbit-webdav",
          "version": "2.14.4",
          "type": "jar",
          "scope": "compile",
          "classifier": "",
          "optional": "false",
          "children": [
            {
              "groupId": "commons-codec",
              "artifactId": "commons-codec",
              "version": "1.10",
              "type": "jar",
              "scope": "compile",
              "classifier": "",
              "optional": "false"
            }
          ]
        }
      ]
    }
  ]
}

Usage Example:

mvn dependency:tree -DoutputType=json -DoutputFile=dependency-tree.json

Use Case: Parse the JSON output programmatically for dependency analysis or integration with other tools.

DOT (outputType=dot)

Description: The DOT format is a plain-text graph description language used by Graphviz. It represents the dependency tree as a directed graph (digraph), with nodes for artifacts and directed edges for dependencies, labeled with their scope (e.g., compile).

Structure:

• Graph Declaration: Starts with digraph "<groupId>:<artifactId>:<type>:<version>:".
• Nodes: Represented implicitly by their identifiers in edge definitions (e.g., "org.apache.maven.extensions:maven-build-cache-extension:jar:1.2.1-SNAPSHOT:").
• Edges: Defined as "source" -> "target", where source is the parent artifact and target is the dependency, optionally labeled with the scope.

Example:

digraph "org.apache.maven.extensions:maven-build-cache-extension:jar:1.2.1-SNAPSHOT:" {
  "org.apache.maven.extensions:maven-build-cache-extension:jar:1.2.1-SNAPSHOT:" -> "net.openhft:zero-allocation-hashing:jar:0.27ea0:compile";
  "org.apache.maven.extensions:maven-build-cache-extension:jar:1.2.1-SNAPSHOT:" -> "org.apache.maven.wagon:wagon-webdav-jackrabbit:jar:3.5.3:compile";
  "org.apache.maven.wagon:wagon-webdav-jackrabbit:jar:3.5.3:compile" -> "org.apache.jackrabbit:jackrabbit-webdav:jar:2.14.4:compile";
  "org.apache.jackrabbit:jackrabbit-webdav:jar:2.14.4:compile" -> "commons-codec:commons-codec:jar:1.10:compile";
}

Usage Example:

mvn dependency:tree -DoutputType=dot -DoutputFile=dependency-tree.dot

Visualization: Convert the DOT file to an image using Graphviz:

dot -Tpng dependency-tree.dot -o dependency-tree.png

Use Case: Visualize the dependency graph using tools like Graphviz for presentations or analysis.

GraphML (outputType=graphml)

Description: GraphML is an XML-based format for representing graphs, compatible with tools like yEd or Gephi. It represents the dependency tree as a directed graph with nodes for artifacts and edges for dependencies, including scope information.

Structure:

• GraphML Root: Contains namespace declarations and keys for node and edge graphics (using yworks.com extensions).
• Graph: Defined with edgedefault="directed".
• Nodes: Each node has an id (a unique number) and a y:ShapeNode with a y:NodeLabel containing the artifact coordinates (e.g., groupId:artifactId:type:version:scope).
• Edges: Defined with source and target node IDs, with a y:PolyLineEdge containing a y:EdgeLabel for the scope (e.g., compile).

Example:

<?xml version="1.0" encoding="UTF-8"?>
<graphml xmlns="http://graphml.graphdrawing.org/xmlns" xmlns:y="http://www.yworks.com/xml/graphml">
  <key for="node" id="d0" yfiles.type="nodegraphics"/>
  <key for="edge" id="d1" yfiles.type="edgegraphics"/>
  <graph id="dependencies" edgedefault="directed">
    <node id="955994360"><data key="d0"><y:ShapeNode><y:NodeLabel>org.apache.maven.extensions:maven-build-cache-extension:jar:1.2.1-SNAPSHOT:</y:NodeLabel></y:ShapeNode></data></node>
    <node id="2058879732"><data key="d0"><y:ShapeNode><y:NodeLabel>net.openhft:zero-allocation-hashing:jar:0.27ea0:compile</y:NodeLabel></y:ShapeNode></data></node>
    <edge source="955994360" target="2058879732"><data key="d1"><y:PolyLineEdge><y:EdgeLabel>compile</y:EdgeLabel></y:PolyLineEdge></data></edge>
    <node id="1889106580"><data key="d0"><y:ShapeNode><y:NodeLabel>org.apache.maven.wagon:wagon-webdav-jackrabbit:jar:3.5.3:compile</y:NodeLabel></y:ShapeNode></data></node>
    <node id="1817415346"><data key="d0"><y:ShapeNode><y:NodeLabel>org.apache.jackrabbit:jackrabbit-webdav:jar:2.14.4:compile</y:NodeLabel></y:ShapeNode></data></node>
    <edge source="1889106580" target="1817415346"><data key="d1"><y:PolyLineEdge><y:EdgeLabel>compile</y:EdgeLabel></y:PolyLineEdge></data></edge>
  </graph>
</graphml>

Usage Example:

mvn dependency:tree -DoutputType=graphml -DoutputFile=dependency-tree.graphml

Visualization: Open the GraphML file in yEd or Gephi to visualize the dependency graph.

Use Case: Analyze complex dependency structures using graph visualization tools.

TGF (outputType=tgf)

Description: The Trivial Graph Format (TGF) is a simple text-based format for representing graphs. It lists nodes followed by edges, with each node and edge described on a single line.

Structure:

• Nodes Section: Each line contains a unique node ID (a number) followed by the artifact coordinates (e.g., groupId:artifactId:type:version:scope).
• Separator: A line containing # separates nodes from edges.
• Edges Section: Each line contains the source node ID, target node ID, and the scope (e.g., compile).

Example:

1474640235 org.apache.maven.extensions:maven-build-cache-extension:jar:1.2.1-SNAPSHOT:
788877168 net.openhft:zero-allocation-hashing:jar:0.27ea0:compile
1662807313 org.apache.maven.wagon:wagon-webdav-jackrabbit:jar:3.5.3:compile
1655562261 org.apache.jackrabbit:jackrabbit-webdav:jar:2.14.4:compile
1894638973 commons-codec:commons-codec:jar:1.10:compile
#
1474640235 788877168 compile
1474640235 1662807313 compile
1662807313 1655562261 compile
1655562261 1894638973 compile

Usage Example:

mvn dependency:tree -DoutputType=tgf -DoutputFile=dependency-tree.tgf

Visualization: Convert TGF to other formats (e.g., DOT) using tools like graphviz or custom scripts for visualization.

Use Case: Lightweight format for simple graph processing or conversion to other graph formats.