Maven Tips and Tricks - 2016

Maven auto-completion
brew tap homebrew/completions

brew install maven-completion
Then add this to ~/.bash_profile:
if [ -f ~/.maven-completion.bash ]; then
  . ~/.maven-completion.bash
fi

Options
-U forces updates, force maven to download/re-download the dependencies
-o Offline
-q,--quiet Quiet output - only show errors

Skip Test
mvn install -DskipTests
This will skip compiling the test:
mvn install -Dmaven.test.skip=true

-DskipTests will compile test classes but not run them
-Dmaven.test.skip=true will skip compiling the tests

How maven resolve versions
Maven uses nearest wins strategy to determine dependency version.
mvn dependency:tree -Dverbose -Dincludes=com.amazonaws:aws-java-sdk-core
[INFO] |  \- com.amazonaws:aws-java-sdk-cloudfront:jar:1.11.32:compile

[INFO] |     \- (com.amazonaws:aws-java-sdk-core:jar:1.11.32:compile - omitted for conflict with 1.11.98)

mvn dependency:build-classpath

Purge dependencies that may be corrupted
mvn dependency:purge-local-repository

Download source jars from maven repository
-DdownloadSources=true -DdownloadJavadocs=true

Download all dependencies into target/dependencies
mvn dependency:copy-dependencies Check how libraries are imported
mvn dependency:tree
Check several specific libraries
mvn dependency:tree -Dverbose -Dincludes=log4j:log4j
Find out conflicted(multiple) version
mvn dependency:tree -Dverbose | grep 'omitted for conflict'

Use dependency:analyze to find out unused dependencies
Use maven-enforcer-plugin(DependencyConvergence) to prevent multiple versions of same library

Use scala-maven-plugin for mixed java/scala projects

Properties
<properties>
  <m2eclipse.wtp.contextRoot>your-app-name</m2eclipse.wtp.contextRoot>
</properties>

Testing
Run specific method
mvn test -Dtest=className#methodName

mvn exec:java -Dexec.mainClass=full.qualified.class -Dexec.classpathScope=test -Dexec.args=local