# Multi-project build - project dependencies and build order **URL:** \ **Category:** Help/Discuss\ **Created:** [October 3, 2016, 7:27pm UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846 "2016-10-03T19:27:38Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Daven53](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/daven53/32/5625_2.png) [@Daven53](https://discuss.gradle.org/u/Daven53)\ **Post date:** [October 3, 2016, 7:27pm UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/1 "2016-10-03T19:27:38Z")
I need to migrate a multi-project build from maven to gradle and maintain the way inter-project dependencies and build order work. I’d like to use the maven plugin in gradle and continue to publish artifacts to both local and remote maven repositories. The multi-project structure is like so: `root/` `--Project-A/` `----Project-A1/` `----Project-A2/` `--Project-B/` `----Project-B1/` `----Project-B2/` In maven _Project-A2_ has a dependency on _Project-A1_. If I run mvn install\_ from the _Project-A2_ directory it will only build/install that project and pull it’s dependency on _Project-A1_ from the local/remote maven repository. If I run mvn install from _Project-A_ it will build/install both _Project-A1_ and _A2_ and calculate the build order based on the above mentioned dependency. How can this same behavior be achieved in gradle? Additionally, _Project-B2_ has a dependency on _Project-A2_. If I run mvn install from the _Project-B2_ or _Project-B_ directories this dependency should be pulled from the local/remote maven repository. If I run mvn install from the _root_ directory it should calculate the build order such that _Project-A1_ builds, \_Project-A2 builds, and then _Project-B2_ builds. ---
**Author:** ![st\_oehme](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/st_oehme/32/5249_2.png) [@st\_oehme](https://discuss.gradle.org/u/st_oehme)\ **Post date:** [October 4, 2016, 9:57am UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/2 "2016-10-04T09:57:04Z")
> [@Daven53](#): > > If I run mvn install\_ from the Project-A2 directory it will only build/install that project and pull it’s dependency on Project-A1 from the local/remote maven repository. Could you explain why you want to mimic this behavior in Gradle? Why not build Project-A1? Gradle has excellent support for incremental builds, so this will be fast and correct. ---
**Author:** ![Daven53](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/daven53/32/5625_2.png) [@Daven53](https://discuss.gradle.org/u/Daven53)\ **Post date:** [October 5, 2016, 9:13pm UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/3 "2016-10-05T21:13:08Z")
The main concern is build time. If it were simply one small project depending on another it’s not really an issue. I’m working with a number of cases where a relatively small project depends on one or more larger projects. If the project I want to build takes 5 minutes but it’s dependencies take 30 minutes it’s not ideal to build both and end up with a 35 minute build time. The incremental build support is great and after building everything once it looks like it should address this need. However I do need to consider the case where someone checks out the source fresh and only wants to build a small piece. They’re not going to want to wait for multiple dependencies to build when they could be pulled in from a repository. ---
**Author:** ![st\_oehme](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/st_oehme/32/5249_2.png) [@st\_oehme](https://discuss.gradle.org/u/st_oehme)\ **Post date:** [October 6, 2016, 8:43am UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/4 "2016-10-06T08:43:27Z")
> [@Daven53](#): > > If the project I want to build takes 5 minutes but it’s dependencies take 30 minutes it’s not ideal to build both and end up with a 35 minute build time. Are these real numbers or hypothetical? Note that the upstream dependencies only need to create their outputs. They won’t run tests or other time-consuming tasks. If your projects actually take that long just to compile, then you might be interested in either: - breaking your big build into smaller builds (inside the same repo) using [Composite Builds](https://docs.gradle.org/current/userguide/composite_builds.html) - our upcoming distributed cache support ---
**Author:** ![Daven53](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/daven53/32/5625_2.png) [@Daven53](https://discuss.gradle.org/u/Daven53)\ **Post date:** [October 6, 2016, 7:59pm UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/5 "2016-10-06T19:59:57Z")
Those numbers are hypothetical but our total build time does reach between 2-3 hours without test and there are cases that exist similar to that example. I’ll take a look at composite builds and the distributed cache support. It sounds like a little restructuring of the projects/process to better fit gradle is the direction to go. Thanks for the suggestions! ---
**Author:** ![st\_oehme](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/st_oehme/32/5249_2.png) [@st\_oehme](https://discuss.gradle.org/u/st_oehme)\ **Post date:** [October 8, 2016, 10:14pm UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/6 "2016-10-08T22:14:10Z")
Maybe I misunderstood your description: Is the 2-3h build time with Maven or Gradle? Gradle is much faster than Maven, so I’d suggest first going with the straightforward multi-project approach and only optimizing if you actually hit a problem. ---
**Author:** ![Daven53](https://sea1.discourse-cdn.com/gradle/user_avatar/discuss.gradle.org/daven53/32/5625_2.png) [@Daven53](https://discuss.gradle.org/u/Daven53)\ **Post date:** [October 11, 2016, 2:52pm UTC](https://discuss.gradle.org/t/multi-project-build-project-dependencies-and-build-order/19846/7 "2016-10-11T14:52:04Z")
2-3 hours in maven. I don’t have an estimate for gradle yet due to trying to work out the best approach ahead of converting the entire maven build to gradle. I’ve only been working with a small piece of our source with gradle. If the best way to tackle this is to setup the multi-project and then look into composite builds, distributed cache support etc. then that’s what I’ll do. I assumed that we would see similar build time/dependency related problems in gradle as we do in maven but if that’s not the case that’s great. Thanks!