Maven dependency example explained
Maven is a project build tool for java and android applications.
One of the features of
ant tool is dependencies management for software projects.
When you are using maven in your project, you need to define the dependencies in pom.xml. Once the dependencies have been configured, they will be downloaded from repositories to your local machine.
When installing with Maven, you must use the dependency plugin to configure the dependencies, which manipulates the artifacts.
So here is the sample code snippet for configuring
spring-core as a dependency to your project in pom..xml of an application.
<project> <dependency> <groupid>org.springframework</groupid> <artifactid>spring-core</artifactid> <version>2.5.6</version> </dependency> </project>
When you run compile or install command in maven, your project downloads the spring-core jar for the first time from the spring repository server.
You also should have to configure the repository server in
pom.xml with the following piece of code.
<repositories> <repository> <id>spring-release</id> <url>http://repository.springsource.com/maven/bundles/release</url> </repository> </repositories>
So you can configure multiple repositories, the order of repositories that looks for the artifact should have to mention in the order in pom.xml
What is a transitive dependency in maven?
For example, Take the scenario, what happened if the
spring-core artifact has
log4j as one of the dependencies.
log4j dependency also download into your local project?
Yes, all the direct dependencies should resolve automatically.
Transitive dependency meaning is that all the dependencies resolve for your projecttransitively` configured in pom.xml.
In this example, your project is configured only as
spring-core, but your project has indirect dependencies
JMX which are dependent on
So maven resolves all these dependencies i.e all direct and indirect dependencies.
spring-core-2.5.6 direct dependency,
jmx-1.0.2 indirect dependencies
As per your project needs, you want to use
log4j-1.2.14 only, but as per the above
spring-core dependency, you got
log4j-1.2.12as a dependency. So you have to avoid the
For this, we have to use an exclusion tag in pom.xml in dependency tag.
Following is the code snippet
<dependency> <groupid>org.springframework</groupid> <artifactid>spring-core</artifactid> <version>2.5.6</version> <exclusions> <exclusion> <groupid>log4j</groupid> <artifactid>log4j</artifactid> </exclusion> </exclusions> </dependency> <dependency> <groupid>log4j </groupid> <artifactid>log4j</artifactid> <version>1.2.14</version> </dependency>
How do you display the maven dependency tree of an application?
It displays a maven dependency tree of project dependencies.
It helps to resolve conflicts with versions of dependencies.
Print Dependency tree for plugins configured in your application?
resolve-plugins will give the plugin dependencies tree of configured dependencies.
Alternatively, You can use the below maven command to print plugin dependencies.
This topic has been a basic start to exploring on maven dependency example. Hopefully, you have enough information to get started.
If you have any questions, please feel free to leave a comment and I will get back to you.