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:

org.eclipse.aether.collection.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:

• ClassicConflictResolver

Nested Class Summary

Nested classes/interfaces inherited from class org.eclipse.aether.util.graph.transformer.ConflictResolver

ConflictResolver.OptionalitySelector, ConflictResolver.ScopeDeriver, ConflictResolver.ScopeSelector, ConflictResolver.Verbosity, ConflictResolver.VersionSelector

Field Summary

Fields

Modifier and Type	Field	Description
static final String	CONFIG_PROP_SHOW_CYCLES_IN_STANDARD_VERBOSITY	This implementation of conflict resolver is able to show more precise information regarding cycles in standard verbose mode.
static final boolean	DEFAULT_SHOW_CYCLES_IN_STANDARD_VERBOSITY

Fields inherited from class org.eclipse.aether.util.graph.transformer.ConflictResolver

CLASSIC_CONFLICT_RESOLVER, CONFIG_PROP_CONFLICT_RESOLVER_IMPL, CONFIG_PROP_VERBOSE, DEFAULT_CONFLICT_RESOLVER_IMPL, NODE_DATA_ORIGINAL_OPTIONALITY, NODE_DATA_ORIGINAL_SCOPE, NODE_DATA_WINNER, PATH_CONFLICT_RESOLVER

Constructor Summary

Constructors

Constructor	Description
PathConflictResolver(ConflictResolver.VersionSelector versionSelector, ConflictResolver.ScopeSelector scopeSelector, ConflictResolver.OptionalitySelector optionalitySelector, ConflictResolver.ScopeDeriver scopeDeriver)	Creates a new conflict resolver instance with the specified hooks.

Method Summary

Modifier and Type	Method	Description
org.eclipse.aether.graph.DependencyNode	transformGraph(org.eclipse.aether.graph.DependencyNode node, org.eclipse.aether.collection.DependencyGraphTransformationContext context)

Methods inherited from class org.eclipse.aether.util.graph.transformer.ConflictResolver

getVerbosity

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

CONFIG_PROP_SHOW_CYCLES_IN_STANDARD_VERBOSITY

public static final String CONFIG_PROP_SHOW_CYCLES_IN_STANDARD_VERBOSITY

This implementation of conflict resolver is able to show more precise information regarding cycles in standard verbose mode. But, to make it really drop-in-replacement, we "tame down" this information. Still, users needing it may want to enable this for easier cycle detection, but in that case this conflict resolver will provide "extra nodes" not present on "standard verbosity level" with "classic" conflict resolver, that may lead to IT issues down the stream. Hence, the default is to provide as much information as much verbose "classic" does.

Since:

2.0.12

See Also:

• Constant Field Values

Sourced from:

RepositorySystemSession.getConfigProperties()

Value type:

Boolean

Default value:

DEFAULT_SHOW_CYCLES_IN_STANDARD_VERBOSITY

DEFAULT_SHOW_CYCLES_IN_STANDARD_VERBOSITY

public static final boolean DEFAULT_SHOW_CYCLES_IN_STANDARD_VERBOSITY

See Also:

• Constant Field Values

Constructor Details

PathConflictResolver

public PathConflictResolver(ConflictResolver.VersionSelector versionSelector,
 ConflictResolver.ScopeSelector scopeSelector,
 ConflictResolver.OptionalitySelector optionalitySelector,
 ConflictResolver.ScopeDeriver scopeDeriver)

Creates a new conflict resolver instance with the specified hooks.

Parameters:

versionSelector - the version selector to use, must not be null

scopeSelector - the scope selector to use, must not be null

optionalitySelector - the optionality selector ot use, must not be null

scopeDeriver - the scope deriver to use, must not be null

Method Details

transformGraph

public org.eclipse.aether.graph.DependencyNode transformGraph(org.eclipse.aether.graph.DependencyNode node,
 org.eclipse.aether.collection.DependencyGraphTransformationContext context)
                                                       throws org.eclipse.aether.RepositoryException

Specified by:

transformGraph in interface org.eclipse.aether.collection.DependencyGraphTransformer

Overrides:

transformGraph in class ConflictResolver

Throws:

org.eclipse.aether.RepositoryException