How to list the Maven build/compilation sequence based on dependencies?

Question

If I have a pom hierarchy in which the superpom calls multiple submodules which depend on one another, how can I list the build/compilation sequence based on dependencies? IOW, if the superpom has modules mod1, mod2, and mod3 and mod2 depends on mod3 and mod3 depends on mod1, then the sequence is mod1, mod3, then mod2. How can I list that order without complex XML parsing of data hierarchies from pom?

Answer 1

What you want to know is the so called reactor build order.

The reactor determines the correct build order from the dependencies stated by each project in their respective project descriptors, and will then execute a stated set of goals. It can be used for both building projects and other goals, such as site generation. (Source: old multi-module documentation)

It collects all modules to build, sorts the projects and builds them in order. It guarantees that any module is build, before it is required by other modules.

As far as I know, there is no direct way of creating only a list of these items, but the closest thing to just get the information is:

mvn validate

It will show your reactor build order on top:

~/parent$ mvn validate
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] simple.parent
[INFO] simple.child
[INFO] simple.anotherchild
[...]                                                                        

No additional work is performed, besides validating the project for correctness and that all necessary information is available.

For more information, see also the guide to working with multiple modules and this answer about what the maven reactor is.

Answer 2

Perhaps you're looking for the Maven dependency:tree option? You'll probably have to adjust the includes to include only your modules. http://maven.apache.org/plugins/maven-dependency-plugin/tree-mojo.html

mvn dependency:tree -Dverbose -DoutputFile=tree.txt -DoutputType=text -Dincludes=com.mycompany.*

Answer 3

Improved version of @rhinoceros.xn:

mvn validate > validate.log

project_name=$(mvn org.apache.maven.plugins:maven-help-plugin:3.1.0:evaluate -Dexpression=project.name -q -DforceStdout)

sed '1,/^\[INFO\] Reactor Build Order:/ d' validate.log | awk '/\[INFO\] -+</ {exit} {print}' | awk '{ print $2 }' | awk \!/^"$project_name"$/ | awk 'NF'