src/site/apt/examples/resolving-conflicts-using-the-dependency-tree.apt

~~ Licensed to the Apache Software Foundation (ASF) under one
~~ or more contributor license agreements.  See the NOTICE file
~~ distributed with this work for additional information
~~ regarding copyright ownership.  The ASF licenses this file
~~ to you under the Apache License, Version 2.0 (the
~~ "License"); you may not use this file except in compliance
~~ with the License.  You may obtain a copy of the License at
~~
~~ http://www.apache.org/licenses/LICENSE-2.0
~~
~~ Unless required by applicable law or agreed to in writing,
~~ software distributed under the License is distributed on an
~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
~~ KIND, either express or implied.  See the License for the
~~ specific language governing permissions and limitations
~~ under the License.    
 
  ------
  Resolving conflicts using the dependency tree
  ------
  Mark Hobson
  ------
  2007-09-01
  ------

Resolving conflicts using the dependency tree

  A project's dependency tree can be expanded to display dependency conflicts.  For example, to find out why Commons
  Collections 2.0 is being used by the Maven Dependency Plugin, we can execute the following in the project's
  directory:

+---+
mvn dependency:tree -Dverbose -Dincludes=commons-collections
+---+

  The <<<verbose>>> flag instructs the dependency tree to display conflicting dependencies that were omitted from the
  resolved dependency tree.  In this case, the goal outputs:
	
+---+
[INFO] [dependency:tree]
[INFO] org.apache.maven.plugins:maven-dependency-plugin:maven-plugin:2.0-alpha-5-SNAPSHOT
[INFO] +- org.apache.maven.reporting:maven-reporting-impl:jar:2.0.4:compile
[INFO] |  \- commons-validator:commons-validator:jar:1.2.0:compile
[INFO] |     \- commons-digester:commons-digester:jar:1.6:compile
[INFO] |        \- (commons-collections:commons-collections:jar:2.1:compile - omitted for conflict with 2.0)
[INFO] \- org.apache.maven.doxia:doxia-site-renderer:jar:1.0-alpha-8:compile
[INFO]    \- org.codehaus.plexus:plexus-velocity:jar:1.1.3:compile
[INFO]       \- commons-collections:commons-collections:jar:2.0:compile
+---+

  Thus we can see that Commons Collections 2.0 was chosen over 2.1 since it is nearer, and by default Maven resolves
  version conflicts with a nearest-wins strategy.

  More specifically, in verbose mode the dependency tree shows dependencies that were omitted for: being a duplicate
  of another; conflicting with another's version and/or scope; and introducing a cycle into the dependency tree.

* Verbose flag support in 3.0+ version

  Support for <<<verbose>>> flag has been removed since maven-dependency-plugin 3.0 ({{{https://issues.apache.org/jira/browse/MDEP-494}MDEP-494}}).
  Extra output can be obtained by using an older version until proper support is reintroduced.

+---+
mvn org.apache.maven.plugins:maven-dependency-plugin:2.10:tree -Dverbose=true
+---+