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Andrei Андрей Листочкин
Andrei Андрей Листочкин

Reputation: 8542

Can someone explain Maven 2 (or 3) dependency resolution to me?

I used Maven before in quite a few projects but they we already configured by someone else. I quickly understood the main concepts (groups, artifacts and versions for jars, local and remote repositories) so I assumed that if I'm asked I'll be able to set up a new project from scratch easily.

That turned out not to be the case when I deal with multiple modules which depend on one another. I poked around maven docs but they are either way too concise or way too technical (sometimes I get a feeling that Maven people wrote it for themselves and not for Maven users). So I'm asking for community help.

Here's a typical scenario:

Three repositories:

I'm building a normal Java EE project consisting of one EJB jar with a corresponding client jar, a web module and a JPA module (I like keeping my entities and all db-connectivity separated from business logic). That gives me 5 project in my IDE:

myapp-jpa is used by myapp-ejb and myapp-web. myapp-ejb-client contains business interfaces for my EJBs.

How should I set all that up? I suspect that I need some kind of parent project but I'm not sure how should I organize inter-project dependency resolution. For example: currently when I specify 

<dependency>
  <groupId>com.mycompany.myapp</groupId>
  <artifactId>myapp-jpa</artifactId>
  <version>0.1-SNAPSHOT</version>
</dependency>

in myapp-ejb's pom.xml maven tries to search for it in my repository and tells me that the .jar can't be found. Even if I build and install all app components into my local repository one by one Maven always fails to build the ear file itself :(

I'd love to get it working under Eclipse or NetBeans.

Upvotes: 3

Views: 746

Answers (1)

javamonkey79
javamonkey79

Reputation: 17765

I think you're on the right path. You need a parent project to pull it all together. In the parent project (and here is the important part) you need your dependencies laid out NOT in the dependency section of your parent pom, rather, you need them in your dependencyManagement section. Then, in your child pom's you can declare dependencies that are in the parent.

The only other gotcha (that I can think of) is that when you check the project using a version control system in Eclipse you need to remember to check the parent project out "as Maven project" otherwise the m2Eclipse plugin tends to freak out and not resolve things properly.

I hope this helps.

Upvotes: 3

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