Does Maven need to explicitly specify the dependency that Spring/Hibernate dependented? - spring

Question

I'm new to Maven, I try to use Maven with Spring, Hibernate in my project. After go though the Spring and Hibernate reference, I found that "there is no need to explicitly specify the dependent liberaries in POM.xml file for such Apache commons liberaries".
My questions is that : If my other parts of project refer to Apache commons liberary, such as commons-io, SHOULD I explicit specify this dependency in POM.xml file?

Answer 1

You should define those dependencies in Maven which your project is using. For example, even though some library depends on commons-io but if your code needs this then you should directly define commons-io in your pom.xml
You should not worry about the dependencies of the libraries you have defined in your pom.xml. Maven will do that for you.

Answer 2

Maven is used to avoid the issue of having to run down JAR files that are dependent on other JAR files. Of course you do not HAVE to use maven to do this, but you should. Maven will automatically download the dependent JAR files of the JAR file you require. THe hibernate-entity manager JAR file, for example, has over 100 dependencies and maven does the work for you.
Anyway,even if you do add the commons-io file to the build path/classpath of the maven project,and then update the project configuration, maven will kick it out.

Answer 3

You can provide a lib name on a site like mvnrepository.com to see what it depends on (e.g. take a look at a section called "This artifact depends on ..." in case of spring-webmvc library). Those dependencies (which your artifact depends on) are called transitive dependencies. You don't have to specify these in your pom.xml as maven will resolve them for you.

Answer 4

For the sake of readability you should only state those dependencies in your module that you rely on directly. You want JUnit to test your software, only declare JUnit; you need hibernate to use ORM, declare hibernate, and so on. Leave the rest to Maven.
And most of the time you should state what you intend to use in the very module you want to use it in. So if you want to use a dependency in more than one module, consider moving it into a dependencyManagement block in a parent pom and referencing it from there in the module you want it in.
parent pom.xml
<dependencyManagement>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
<scope>test</scope>
</dependency>
</dependencies>
</dependencyManagement>
child pom.xml
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
</dependency>
</dependencies>
This guarantees you version-stability and still allows you to find out what a module uses by only looking in it's pom (and not all over the place).