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Maven: Dependency to pom module is not include submodules from it

Project have next structure:
root
|
+--Module 1
| |
| +--Submodule_1
| |
| +--Submodule_2
| |
| +--Submodule_N
|
+--Module 2
Module 2 depend on Module 1 and expected access to classes from submodules 1..N
Root pom.xml:
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>root</artifactId>
<version>master</version>
<packaging>pom</packaging>
<modules>
<module>Module_1</module>
<module>Module_2</module>
</modules>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
</project>
Module 1 pom.xml:
<project>
<parent>
<groupId>com.example</groupId>
<artifactId>root</artifactId>
<version>master</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>Module_1</artifactId>
<packaging>pom</packaging>
<modules>
<module>Submodule_1</module>
<module>Submodule_2</module>
...
<module>Submodule_N</module>
</modules>
</project>
Submodule_N pom.xml:
<project>
<parent>
<groupId>com.example</groupId>
<artifactId>Module_1</artifactId>
<version>master</version>
<relativePath>../pom.xml</relativePath>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>Submodule_N</artifactId>
</project>
Module 2 pom.xml:
<project>
<parent>
<groupId>com.example</groupId>
<artifactId>root</artifactId>
<version>master</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>Module_2</artifactId>
<dependencies>
<dependency>
<groupId>com.example</groupId>
<artifactId>Module_1</artifactId>
<version>master</version>
<scope>compile</scope>
</dependency>
</dependencies>
</project>
So this configuration fail with error package com.example.submodule_n.x.y does not exist.
If add dependency from module 1 to submodule_n than package will be found but maven fail with error ...is referencing itself.
One working case if add dependency from module 2 to submodule_n. But expected way when module 2 will have only one dependency to module 1 for include all submodules from module 1.
It is can do gradle, but I don't have any ideas how it implement using maven.

One working case if add dependency from module 2 to submodule_n. But expected way when module 2 will have only one dependency to module 1 for include all submodules from module 1
That is your expectations that are actually not valid.
The purpose of configuration like:
<modules>
<module>Submodule_1</module>
<module>Submodule_2</module>
...
<module>Submodule_N</module>
</modules>
is to somehow organise project structure, it have nothing in common with dependencies between java libraries (though, it affects build lifecycle), moreover, the configuration like:
<dependencies>
<dependency>
<groupId>com.example</groupId>
<artifactId>Module_1</artifactId>
<version>master</version>
<scope>compile</scope>
</dependency>
</dependencies>
in general does not make sense because library may not depend on pom - actually that just tells maven to build Module_2 after Module_1.
Summarising statements above: if Module_2 depends on Submodule_N you must explicitly define that dependency in pom.xml

Parent POM vs Super POM - are they same?

I want to understand if Parent POM and Super POM are same or are there still differences.
Take below maven poms, I declare a parent pom as below:
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.demo</groupId>
<artifactId>deps</artifactId>
<packaging>pom</packaging>
<version>0.0.1-SNAPSHOT</version>
<dependencyManagement>
<dependencies>
<!-- not relevant for this question -->
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.3.12</version>
</dependency>
</dependencies>
</project>
Now I declare a child pom as below:
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.demo</groupId>
<artifactId>deps2</artifactId>
<version>0.0.1-SNAPSHOT</version>
<parent>
<groupId>com.demo</groupId>
<artifactId>deps</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<dependencies>
<!-- not relevant for this question -->
</dependencies>
</project>
Now deps is the parent pom for deps2. I am not sure if I can also call deps as super pom for deps2.
Which of the below inheritance hierarchy is correct
dep2 --> deps end (NO Maven provided super pom)
dep2 --> deps --> Maven provided super pom end

Option 2, because all models implicitly inherit from the Super POM.
deps is a parent for deps, but not the Super POM.
This is according to the definitions on the website.
What is more ... if you inspect the effective POM, you will see that it will always inherit from the Super POM on the MVN website.

How to specify maven properties in a aggregator POM?

I have a project structure like below.In aggregator POM project1 and project 2 are defined as modules.Now if i want to add a maven property that can be accessed in all the projects how can i do it?.
What is the best project structure in this case.?
If i define property like <temp.dir>data</temp.dir> in the aggregator POM then it is not available in project1 pom.xml and project2 POM.xml.I have to duplicate the same property in both the POM's.
project
- project1
- - pom.xml ---- has parent POM as project A
- project2
- - pom.xml --- has parent POM as project B
- pom.xml (Aggregator POM)
UPDATE:To clarify more project1 pom and project 2 has different parent POM's.So aggregator POM cannot be set as parent.

You need to set the aggregator pom as the parent of project1 and project2.
eg. in project1 and project2 poms add:
<parent>
<groupId>com.agr</groupId>
<artifactId>project-aggregator</artifactId>
<version>1.0.0</version>
</parent>
EDIT:
I understand that project1 and project2 have different parent poms.
The only solution i know about to achieve what You want is to store the properties in parent pom.
I can think only of one solution, to make an inheritance chain:
Project2Parent:
<parent>
<groupId>com.test</groupId>
<artifactId>Project1Parent</artifactId>
<version>0.0.1</version>
</parent>
<artifactId>Project2Parent</artifactId>
<version>0.0.1</version>
Aggregator:
<parent>
<groupId>com.test</groupId>
<artifactId>Project2Parent</artifactId>
<version>0.0.1</version>
</parent>
<artifactId>Aggregator</artifactId>
<version>0.0.1</version>
Project1
<parent>
<groupId>com.test</groupId>
<artifactId>Aggregator</artifactId>
<version>0.0.1</version>
</parent>
<artifactId>project1</artifactId>
<version>0.0.1</version>
Project2
<parent>
<groupId>com.test</groupId>
<artifactId>Aggregator</artifactId>
<version>0.0.1</version>
</parent>
<artifactId>project2</artifactId>
<version>0.0.1</version>

Here is aggregator's pom:
<groupId>y</groupId>
<artifactId>y</artifactId>
<version>0.0.1</version>
<packaging>pom</packaging>
<modules>
<module>y1</module>
<module>y2</module>
</modules>
<properties>
<x>1</x>
</properties>
This is y1 effective pom (generated by Eclipse):
<parent>
<groupId>y</groupId>
<artifactId>y</artifactId>
<version>0.0.1</version>
</parent>
<groupId>y1</groupId>
<artifactId>y1</artifactId>
<version>0.0.1</version>
<properties>
<x>1</x>
</properties>
As you can see property x declared in parent is inherited by child.

Cyclic reference error in maven

Good day,
I am getting an error saying: 'The projects in the reactor contain a cyclic reference'.
Parent pom.xml:
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>com.solveit.cmr</groupId>
<artifactId>cmr-parent</artifactId>
<version>1.0.0-SNAPSHOT</version>
<packaging>pom</packaging>
<name>cmr-parent</name>
<modules>
<module>cmr-core</module>
</modules>
<dependencies>
<dependency>
<groupId>com.solveit.cmr.core</groupId>
<artifactId>cmr-core</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
</project>
child pom:
<modelVersion>4.0.0</modelVersion>
<artifactId>cmr-core</artifactId>
<name>cmr-core</name>
<groupId>com.solveit.cmr.core</groupId>
<parent>
<groupId>com.solveit.cmr</groupId>
<artifactId>cmr-parent</artifactId>
<version>1.0.0-SNAPSHOT</version>
</parent>
How can I fix this problem?
Thank you

The <modules> section tell maven the hierarchy between the parent pom and childs pom.
The parent should contain all the common section to all the modules.
such as <dependencyManagement>, <plugins> and <properties>

Maven include parent classes

I have a fairly simple maven-ized Java project, but am having trouble getting my head around it.
My parent module defines a lot of Java classes (and dependencies) that I expect to be useful for several child modules. One of the child modules is dedicated to deploying a web app, so it needs a few extra classes (the servlets) plus everything from the parent module.
The file structure looks like this
- parent
- src
- pom.xml
- child
- src
- pom.xml
My parent pom looks like this:
<project>
<groupId>my.group</groupId>
<artifactId>parent</artifactId>
<version>0.0.1</version>
<packaging>pom</packaging>
...
<modules>
<module>child</module>
</modules>
</project>
And the child looks like this:
<project>
<artifactId>child</artifactId>
<packaging>war</packaging>
<parent>
<artifactId>parent</artifactId>
<groupId>my.group</groupId>
<version>0.0.1</version>
</parent>
...
</project>
Is this all I need to have the child know about the classes and dependencies defined in parent? It doesn't seem to be: eclipse gives compile errors, and running mvn clean package from parent folder or child folder results "cannot find symbol" messages any time a class from parent is mentioned.
What am I doing wrong?

I'd change the structure of your project like this:
parent (pom)
core (jar, with all the classes that used to be in parent)
child (war, depends on core)
Parent:
<project>
<groupId>my.group</groupId>
<artifactId>parent</artifactId>
<version>0.0.1</version>
<packaging>pom</packaging>
<modules>
<module>core</module>
<module>child</module>
<!-- possibly more modules... -->
</modules>
</project>
Core:
<project>
<parent>
<groupId>my.group</groupId>
<artifactId>parent</artifactId>
<version>0.0.1</version>
</parent>
<artifactId>core</artifactId>
<packaging>jar</packaging>
</project>
Child:
<project>
<parent>
<groupId>my.group</groupId>
<artifactId>parent</artifactId>
<version>0.0.1</version>
</parent>
<artifactId>module1</artifactId>
<packaging>war</packaging>
<dependencies>
<dependency>
<groupId>my.group</groupId>
<artifactId>core</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
</project>

Since your parent module's packaging is "pom", no jar file will be provided and no .class file from that will be accessible to other modules. Try changing it to "jar" and give it another try.
Although it's not a good practice to have a parent as "jar". I'd stick to the "pom" parent and probably create a new "core" or "common" child and make my "war" depend on it.

Try to add an internal dependency in child module pom, so it is familiar with its parent
<dependency>
<groupId>my.group</groupId>
<artifactId>parent</artifactId>
<version>0.0.1</version>
</dependency>

The first thing you should do is to define your dependencies within a dependencyManagmeent block in your parent like this:
<dependencyManagement>
<dependencies>
<dependency>
<groupId>group-a</groupId>
<artifactId>artifact-a</artifactId>
<version>1.0</version>
</dependency>
...
</dependencies>
</dependencyManagement>
and furthermore in your child you should say which dependency your child would like to use as dependency:
<dependencies>
<dependency>
<groupId>group-a</groupId>
<artifactId>artifact-a</artifactId>
<!-- No version given. See dependencyManagement -->
</dependency>
...
</dependencies>