Maven BOM [Bill Of Materials] Dependency

If you have worked on maven in your projects for dependency management, then you must have faced one problem at least once or may be more than that. And the problem is version mismatch. It generally happens when you got some dependencies which bring it’s related dependencies together with certain version. And if you have included those dependencies with different version numbers already, they can face undesired results in compile time as well as runtime also.

Ideally to avoid above issue you need to explicitly exclude the related dependency, but it is quite possible that you can forget to do so.

How to add BOM [Bill Of Materials] dependency

Maven provides a tag dependencyManagement for this purpose. You need to add the bom information in this tag as follows. I am taking the example of Spring bom file.

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-framework-bom</artifactId>
            <version>4.0.1.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

An added benefit of using the BOM is that you no longer need to specify the version attribute when depending on Spring Framework artifacts. So it will work perfectly fine.

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
    </dependency>
<dependencies>

Each project has it’s own bom file

Please note that there is no common or universal bom file. Each project (if support this feature) provides its own bom file and manages versions of it’s related dependencies.

Few example of various bom files are below:

1) RESTEasy BOM dependency

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.jboss.resteasy</groupId>
			<artifactId>resteasy-bom</artifactId>
			<version>3.0.6.Final</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

2) JBOSS BOM dependency

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.jboss.bom</groupId>
			<artifactId>jboss-javaee-6.0-with-tools</artifactId>
			<version>${some.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement> 

3) Spring BOM dependency

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-framework-bom</artifactId>
            <version>4.0.1.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

4) Jersey BOM dependency

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.glassfish.jersey</groupId>
            <artifactId>jersey-bom</artifactId>
            <version>${jersey.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

Those are few examples. So whenever you work next time in maven, try to explore this feature.

Happy Learning !!