Why is spring-boot-dependencies in dependencyManagement? - maven

Question

The Spring documentation Using Spring Boot without the parent POM shows that the dependency on spring-boot-dependencies is added to the dependencyManagement section. Is this really correct?
spring-boot-dependencies specifies version properties for all the dependencies. However, these properties are not available in the POM that uses spring-boot-dependencies. Presumably, this is because spring-boot-dependencies is in dependencyManagement.
spring-boot-dependencies only includes dependencyManagement and pluginManagement. So it seems possible to include spring-boot-dependencies as a dependency (not dependencyManagement) without adding unnecessary dependencies.
So why is spring-boot-dependencies to be included as dependencyManagement?

Answer 1

So why is spring-boot-dependencies to be included as dependencyManagement?
Let's say you have a project named projectA and you add the spring-boot-dependencies to the dependencyManagement section in your pom.xml.
<project>
<groupId>com.iovation.service</groupId>
<artifactId>projectA</artifactId>
<version>1.0.0-SNAPSHOT</version>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<type>pom</type>
<version>1.5.8.RELEASE</version>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<!-- Spring Boot Dependencies -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
...
</project>
If you notice closely, you will find that all the Spring Boot dependencies declared under the dependencies section don't need to specify the version. It derives the version from the version of spring-boot-dependencies specified in the dependencyManagement section.
Advantages of Dependency Management
It centralizes dependency information by specifying the Spring Boot version at one place. It really helps during upgrade from one version to another.
Subsequent declaration of Spring Boot dependencies just mentions the library name without any version. Especially helpful in multi-module projects
It avoids mismatch of different versions of spring boot libraries in a project.
No Conflicts.

Answer 2

It's definitely correct. Please see Using Spring Boot without the parent POM!

Answer 3

First, let’s understand what dependency is. So when you are developing an application, you would probably need a number of libraries(normally jar files). It means that your application depends on these libraries. Hence the name dependency.
Now you need a way to assemble all these libraries and manage them in a centralized fashion. This also means that these libraries would be made available at compile time or runtime when needed. This is what dependency management does.
So the process of dependency management involves locating these dependencies and adding them to the classpath.
Maven is a popular dependency management tool which will centralize all dependencies information.