Figuring out duplicate dependency in war

Question

Could someone explain how do people get duplicate dependencies with different versions in their war? Maybe give some examples

I cannot understand for the live of me. Maven2 has dependency mediation for transitive dependencies

Say I have:

A
- B
- C

B
- E

Now in a project X, with war packaging I add A and B as dependency.

Because of the aforementioned dependency mediation, regardless of the version of B from project A, in the war I will see a single B jar with the declared version in X.

This because maven will use the version of the closest dependency to my project.

So, what am I missing here? How do people mess this up? Looking forward to enlightenment

Just to be clear, the same thing happens with transitive dependencies further along the dependency tree. The closest one to the project is chosen — Capp Argo
Dunno about WARs but I have seen people getting duplicated dependencies in EARs easily. — Hubert Grzeskowiak

Sumit Kumar Sumit Kumar · Accepted Answer · 2017-02-08T13:09:28

For conflicting jars with same groupId and artifactId , maven takes the version coming from the dependency declared at last .

You can play with dependency order. Just change the dependency order of A and B in project X .

Scenario 1 : Here since 2.5 is added after 2.3 , 2.5 wil be packaged.

<dependencies>

        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
            <version>2.3</version>

        </dependency>

        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
            <version>2.5</version>

        </dependency>

    </dependencies>

Scenario 2 : Here since 2.3 is added after 2.5 , 2.3 wil be packaged.

<dependencies>

            <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
            <version>2.5</version>

        </dependency>

        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
            <version>2.3</version>

        </dependency>

    </dependencies>

You can also try exclusion concept here.

Figuring out duplicate dependency in war

1 Answers