Package org.eclipse.aether.util.graph.transformer

Class PathConflictResolver

java.lang.Object
org.eclipse.aether.util.graph.transformer.ConflictResolver
org.eclipse.aether.util.graph.transformer.PathConflictResolver
All Implemented Interfaces:
DependencyGraphTransformer
public final class PathConflictResolver extends ConflictResolver
A high-performance dependency graph transformer that resolves version and scope conflicts among dependencies. This is the recommended conflict resolver implementation that provides O(N) performance characteristics, significantly improving upon the O(N²) worst-case performance of ClassicConflictResolver.

For a given set of conflicting nodes, one node will be chosen as the winner. How losing nodes are handled depends on the configured verbosity level: they may be removed entirely, have their children removed, or be left in place with conflict information. The exact rules by which a winning node and its effective scope are determined are controlled by user-supplied implementations of ConflictResolver.VersionSelector, ConflictResolver.ScopeSelector, ConflictResolver.OptionalitySelector and ConflictResolver.ScopeDeriver.

Performance Characteristics:

  • Time Complexity: O(N) where N is the number of dependency nodes
  • Memory Usage: Creates a parallel tree structure for conflict-free processing
  • Scalability: Excellent performance on large multi-module projects

Algorithm Overview:

  1. Path Tree Construction: Builds a cycle-free parallel tree structure from the input dependency graph, where each Path represents a unique route to a dependency node
  2. Conflict Partitioning: Groups paths by conflict ID (based on groupId:artifactId:classifier:extension coordinates)
  3. Topological Processing: Processes conflict groups in topologically sorted order
  4. Winner Selection: Uses provided selectors to choose winners within each conflict group
  5. Graph Transformation: Applies changes back to the original dependency graph

Key Differences from ClassicConflictResolver:

  • Performance: O(N) vs O(N²) time complexity
  • Memory Strategy: Uses parallel tree structure vs in-place graph modification
  • Cycle Handling: Explicitly breaks cycles during tree construction
  • Processing Order: Level-by-level from root vs depth-first traversal

When to Use:

  • Default choice for all new projects and Maven 4+ installations
  • Large multi-module projects with many dependencies
  • Performance-critical build environments
  • Any scenario where ClassicConflictResolver shows performance bottlenecks

Implementation Note: This conflict resolver builds a cycle-free "parallel" structure based on the passed-in dependency graph, and applies operations level by level starting from the root. The parallel Path tree ensures that cycles in the original graph don't affect the conflict resolution algorithm's performance.

Since:
2.0.11
See Also: