Why do we need exclude in pom

Question

Pom.xml have this elements and I am curious why do we need exclude commons-logging from spring-core? And how do it works?

<dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>3.0.5.RELEASE</version>
        <type>jar</type>
        <scope>compile</scope>
        <exclusions>
            <exclusion>
                <artifactId>commons-logging</artifactId>
                <groupId>commons-logging</groupId>
            </exclusion>
        </exclusions>
    </dependency>
<!-- next is log4j dependencie -->

score 0 · Accepted Answer · answered Jan 21 '16 at 15:53

0

I have seen and done the similar things before, the reason is simple:

To exclude commons-logging library because I want to use log4j instead.

So you tell maven to not include the unnecessary library, and to do that use < exclusion >.

answered Jan 21 '16 at 15:53

OPK

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score 0 · Answer 2 · answered Jan 21 '16 at 15:54

0

You are probably using a different version of commons-logging in your program than the one that is defined by spring-core 3.0.5.RELEASE. Check the dependecies of your program and see if there is another commons-logging defined.

answered Jan 21 '16 at 15:54

JFPicard

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score 0 · Answer 3 · answered Jan 21 '16 at 15:56

In the example above spring-core itself has a dependency on commons-logging so it will pull that jar into the project. For what ever reason the user did not want the commons-logging that comes with spring-core, they may want to use another version.

It is possible to have 2 dependencies which have sub dependencies that clash with each other, although I would say this is rare. Usually excludes can be used sparingly.

Why do we need exclude in pom

3 Answers3