How can a root have a parent?

Question

Trying to solve some my problems and looking at many wise discussions such as:

I came to a conclusion that I do not understand something absolutely basic in all that stuff about POMs.

How can a POM that is a root one, have a parent or even maybe parents?

It seems that maven has special interpretation of what is the parent and what is the root. But I am afraid that all documentation that I have found takes such simple terms for something already known. Sorry, they are not such for me.

The root mechanism and the parent mechanism are not overlapping. You can have both in the same pom.xml. — Thorbjørn Ravn Andersen, Oct 30 '17 at 13:33
Parent is a reference to another pom. OK. What is 'root' them? — Gangnus, Oct 30 '17 at 13:50

Pramod S. Nikam · Accepted Answer · 2017-10-30T13:11:46.170

1

So as to explain a bit about How root POM have Parent I need to take help of example.

Whenever we initialize any project using Spring Boot then we use following parent definition in pom.xml

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.8.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

Now this parent definition facilitate inheritance of common managed dependencies needed to for your application to behave in Spring boot way. These parents have their own pom.xml and those pom mentions common dependencies. Maven central repositories understands these Poms. So this is kind of pom to pom inheritance.

Few of examples of inherited managed dependencies are: 1. Logging using slf4j 2. testing using junit

and so on... and so many..

So here opinionated Spring Boot Project becomes parent project and your maven root pom.xml become beneficiary.

edited Oct 30 '17 at 13:11

answered Oct 30 '17 at 09:30

Pramod S. Nikam

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Yes, that example looks like that mess I have in my project... And how the maven knows where to look for that parent? For we don't have any URL or file here. – Gangnus Oct 30 '17 at 09:41
So, that "parent" is practically something as a used library/repository? What is the difference between "parent" and "dependency" then? – Gangnus Oct 30 '17 at 09:42
@Gangnus - These parents have their own pom.xml and those pom mentions common dependencies. Maven central repositories understands these Poms. – Pramod S. Nikam Oct 30 '17 at 10:21
So this is kind of pom to pom inheritance. – Pramod S. Nikam Oct 30 '17 at 10:22
But then in what sense the root POM is root? I thought that means that others POMs depend on it and it does not depend on anything. – Gangnus Oct 30 '17 at 10:26
Its root from application or domain perspective – Pramod S. Nikam Oct 30 '17 at 11:09
Could you add that additional info from comments into the answer - I will gladly check it as the answer then. – Gangnus Oct 30 '17 at 12:40
Yeah I have added that in answer – Pramod S. Nikam Oct 30 '17 at 13:11

How can a root have a parent?

How can a POM that is a root one, have a parent or even maybe parents?

1 Answers1