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Spring boot multi module maven projects without repository

I have multiple spring boot projects, every project is independent and has its own CICD pipeline.
These projects need some common classes, I have created a separate project with common classes.
Parent
pom.xml (with packaging)
lib-project
pom.xml
project-1
pom.xml
project-2
pom.xml
I can build project easily from the parent directory, it builds all the projects
parent$ mvn clean package
it generates all the jar files and put them in their respective target folder of projects
My problem is I can't initiate this at the parent level, this has to be initiated from within each project from its own pipeline.
and
I cannot use any local or remote repository, to put the dependent jar in m2 using mvn clean install and then refer to it as dependency
I want to build it from the relavent project directory
parent/project-1$ mvn clean package
it shows following error:
Could not resolve dependencies for project com.test.multiple:project-1:jar:0.0.1-SNAPSHOT: Could not find artifact com.test.multiple:lib-project:jar:0.0.1-SNAPSHOT
My expectation stepwise on compilation of project-1
Check if there is a dependency for project-1
Go to ../lib-project
Compile and build it in target folder (or anywhere relative to our project)
Add this generated jar to "project-1" dependency
Compile and build the "project-1" jar file.
Parent Pom Configurations
<project ...>
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.test.multiple</groupId>
<artifactId>parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>pom</packaging>
<modules>
<module>lib-project</module>
<module>project-1</module>
</modules>
</project>
** Lib project pom **
<project ...>
<parent>
<groupId>com.test.multiple</groupId>
<artifactId>parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<groupId>com.test.multiple</groupId>
<artifactId>lib-project</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>lib-project</name>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>
Project-1 pom
<project ...>
<parent>
<groupId>com.test.multiple</groupId>
<artifactId>parent</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<groupId>com.test.multiple</groupId>
<artifactId>project-1</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>project-1</name>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.test.multiple</groupId>
<artifactId>lib-project</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

I have multiple spring boot projects, every project is independent and has its own CICD pipeline.
These projects need some common classes, I have created a separate project with common classes.
Congratulations, your projects are not independent any more!
Given the definitions above, here are the dependencies:
lib-project depends on parent;
project-1 depends on parent;
project-1 depends on lib-project.
Please check Introduction to the POM and Guide to Working with Multiple Modules for the discussion on the dependencies in Maven projects.
I cannot use any local or remote repository, to put the dependent jar in m2 using mvn clean install and then refer to it as dependency
Given this limitation, and dependencies listed above, the POMs and source files of all the projects have to be present on the disk for build purposes. The build process has to start from the parent folder. The build process has to build all modules at once.
Also, please consider using mvn clean verify instead of mvn clean install to avoid populating the local repository with the artifacts you are building.

A maven project isn't designed to build its dependencies on demand. However, jenkins can be configured to build downstream projects when changes are pushed to an upstream dependency.
I have also worked around this by using the -pl option on a parent pom in the relevant jenkinsfile to build a subset of the child projects
Jenkinsfile
clone parent project
mvn clean package -pl core,deployable

Spring Tool Suite Maven project error in pom.xml at xsi:schemaLocation

I just started my first maven project, but got error at the very first line of pom.xml file at the xsi:schemaLocation part.
My pom.xml is
<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
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example.demo</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>Demo Course API</name>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<properties>
<java.version>1.8</java.version>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>2.4.2</version>
</plugin>
</plugins>
</build>
</project>
The first few lines of error description are
Failure to transfer com.fasterxml.jackson.core:jackson-annotations:jar:2.9.0 from https://repo.maven.apache.org/maven2 was cached in the
local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not
transfer artifact com.fasterxml.jackson.core:jackson-annotations:jar:2.9.0 from/to central (https://repo.maven.apache.org/maven2): The operation was
cancelled. org.eclipse.aether.transfer.
I just copied it from the spring getting started guides but still got the error.don't know what to do.
My mvn -v is 3.5.2

There is incompatibilities between the version of M2E and the version 3.1.2 of the maven-jar-plugin.
Until the problem is solved by the development teams of M2E or maven-jar-plugins, you have to add in your pom.xml file the following line in order to solve this issue:
</project>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.1.1</version>
</plugin>
</plugins>
</pluginManagement>
</build>

Try including this dependency in your pom.xml and check:
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-annotations</artifactId>
<version>2.9.0.pr2</version>
</dependency>

Analyzing the error description helped a lot in solving the above problem.
The error count was 53.
First as stated by #Duho adding the jackson dependency helped in reducing some error, now the error count reduced to 35.
Then the error was in the hibernate validator dependency, i fixed this by adding the hibernate validator dependency.
Dependencies can be added by right clicking the project-->Maven-->Add Dependency .
Then i found out that maven downloaded some incompleted files from central repository to local repository, the download was incomplete. So, i deleted all files with ".lastUpdated" extension from Users/'myName'/.m2/repository folder.
Then by updating the project from right click-->Maven-->Update Project helped in solving all the errors.
It worked for me.. hope this works for anyone with the same problem.

Maven generate jar dependencies then war

I'm using m2e Maven Plugin for Eclipse. I'm having 5 eclipse projects. A web application project and then 4 projects as jars dependencies for my web application.
I would like to know how can I package jars before including them in the WAR using "mvn clean install" on war project.
Here's my pom.xml:
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>dispatcher</groupId>
<artifactId>dispatcher</artifactId>
<version>4.0</version>
<packaging>war</packaging>
<build>
<plugins>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>2.3</version>
<configuration>
<warSourceDirectory>WebContent</warSourceDirectory>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>referentiel</groupId>
<artifactId>referentiel</artifactId>
<version>4.7</version>
</dependency>
<dependency>
<groupId>mailTemplates</groupId>
<artifactId>mailTemplates</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>qualityTool</groupId>
<artifactId>qualityTool</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>tools</groupId>
<artifactId>tools</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
...
..
.
</dependencies>
</project>
Thank you in advance.

The answer of #Jigar Joshi is good but i thing you need a view of structure which can help you to understand quickly what we mean.
I. Create a top level maven module (parent of war and jars)
You habe already the 5 moduls that you need. Now create a new Maven project as parent which must contain only a pom.xml file.
parent project pom
<project...>
<groupId>groupId</groupId>
<artifactId>parent-pom</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<name>Define parent pom </name>
<!-- modul -->
<project>
II. Put your jar projects first as modul and at the end the war project. If you have another dependencies in the jar projects you may also try to order them consequently.
parent project pom
<modules>
<module>referentiel</module> <!-- jar -->
<module>mailTemplates</module> <!-- jar -->
<module>qualityTool</module> <!-- jar -->
<module>tools</module> <!-- jar -->
<module>dispatcher</module> <!-- war-->
</modules>
III. in all other project put the parent reference into the poms
<parent>
<groupId>groupId</groupId>
<artifactId>parent-pom</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
IV. Now you can go to inside the new created parent project and run from there
mvn clean install

Either create a top level maven module (parent of war and jars) and execute mvn clean install
---pom.xml
|
|dispatcher---pom.xml (war)
|qualityTool----pom.xml (jar)
|mailTemplates----pom.xml (jar)
|referentiel----pom.xml (jar)
|tools----pom.xml (jar)
or use --also-make command line option to make dependencies as well

How to define organization specific parent pom

Env: Maven 2.2.1
I have two java projects under svn (projectA, projectB). My maven structure is as follows..
For projectA
pom.xml (contains ProjectA parent pom definitions)
module moduleA
module moduleB
For projectB
pom.xml (contains ProjectB parent pom definitions)
module moduleC
module moduleD
projectA/pom.xml and projectB/pom.xml contain common definitions like junit, selenium, compiler, eclipse plug-ins which are common to both projects. (e.g. given below)
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.4</version>
<type>jar</type>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.7</version>
<scope>test</scope>
</dependency
How should I create / organize a organization specific project pom which includes such common definitions, so that individual projects don't have to re-create / maintain one. Can someone provide some snippets or projects which have already done this before?
EDIT1:
company/pom.xml
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany</groupId>
<artifactId>company</artifactId>
<packaging>pom</packaging>
<name>parent</name>
<version>1.0.0</version>
<build>
<defaultGoal>install</defaultGoal>
</build>
<dependencies>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.4</version>
<type>jar</type>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
<scope>provided</scope>
</dependency>
</dependencies>
projectA/pom.xml
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.mycompany</groupId>
<artifactId>company</artifactId>
<version>1.0.0</version>
</parent>
<groupId>com.mycompany</groupId>
<artifactId>projectA</artifactId>
<packaging>pom</packaging>
<name>projectA</name>
<version>1.0.0</version>
<modules>
<module>moduleA</module>
<build>
<defaultGoal>install</defaultGoal>
</build>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
projectA/moduleA/pom.xml
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.mycompany</groupId>
<artifactId>projectA</artifactId>
<version>1.0.0</version>
<relativePath>../pom.xml</relativePath>
</parent>
<groupId>com.mycompany</groupId>
<artifactId>moduleA</artifactId>
<version>1.0.0</version>
<packaging>jar</packaging>
<name>moduleA</name>
<build>
<finalName>moduleA</finalName>
<defaultGoal>install</defaultGoal>
</build>
<dependencies>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
</dependency>
</dependencies>
Throws the following error:
Project ID: com.mycompany:moduleA
POM Location: c:\temp\maven\projectA\moduleA\pom.xml
Validation Messages:
[0] 'dependencies.dependency.version' is missing for commons-lang:comm
ons-lang:jar
[1] 'dependencies.dependency.version' is missing for javax.servlet:ser
vlet-api:jar

I would seriously reconsider adding dependencies into a "super" POM, this unnecessarily couples the projects (but may hint that if the projects aren't disparate then they should be merged anyway).
I think the last comment by #lexicore is poignant too, to expand on the OOP analogy it also feels like "mixing levels of abstraction".
Alex Gitelman provides the correct answer, you need to use dependencyManagement as shown here Dependency Scope
Maven3 is supposed to be supporting POM fragments see How to use Maven 3 mixins? which I've long been waiting for.
We have an organisation Über POM but this just contains:
<organization>
<name>...</name>
<url>...</url>
</organization>
<developers>
<developer>
<id>...<id>
<name>...</name>
<email>...</email>
<roles>
<role>...</role>
</roles>
</developer>
<distributionManagement>
...
</distributionManagement>
<repositories>
<!-- your proxy repo here -->
</repositories>
These are things that change very rarely (if we change our repository/distribution-management then all projects must change, if a developer leaves or joins we can update the project POMs at any time convenient).
Dependencies belong specifically to the module under consideration, just because two independent project happen to share dependencies now doesn't mean they always will. I completely understand the annoyance of having to copy 'n' paste reams of XML for each project (compiler plugin, reporting plugins, junit etc), but differing levels of activity in each project will surely mean they diverge at some point.
WRT cascade builds in Continuous Integration, if project A demands a change in the super dependencies POM, then all you other projects will be forced to rebuild - maybe fine if you've only 2 projects but even then did you checkout and build both before committing the change?

If it's only dependencies that you need to reuse, create another project with packaging pom and specify dependencies there. Let's call it OrgDependencies Then include it as dependency in your projectA and projectB. It will transitively pull all dependencies from OrgDependencies project.
In your example, in projectA, instead of
<parent>
<groupId>com.mycompany</groupId>
<artifactId>company</artifactId>
<version>1.0.0</version>
</parent>
Try putting
<dependencies>
<dependency>
<groupId>com.mycompany</groupId>
<artifactId>company</artifactId>
<version>1.0.0</version>
</dependency>
</dependencies>
And remove dependencies to commons-lang etc from modules.
Update.
While my previous solution with transitive dependencies should work, actually what you need
is <dependencyManagement> section in your company wide pom.xml
That's where you define versions.
Note: Anything in dependencyManagement section is not really a dependency but just a descriptor that allows to specify version and exclude transitive dependencies (if necessary) in case normal dependencies section specifies that dependency. So you can put as many items in dependencyManagement as you want, it will not make all descendants dependent on them.
I tested it and it works:
<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.mycompany</groupId>
<artifactId>company</artifactId>
<packaging>pom</packaging>
<name>parent</name>
<version>1.0.0</version>
<build>
<defaultGoal>install</defaultGoal>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>commons-lang</groupId>
<artifactId>commons-lang</artifactId>
<version>2.4</version>
<type>jar</type>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
<scope>provided</scope>
</dependency>
</dependencies>
</dependencyManagement>
</project>

In OS projects I am normally using 3+ levels of POMs:
"Company-wide POM" contains dev-wide definitions like distribution management, individual plugin versions etc. Very stable, normally has one-number version. Example: Sonatype OSS Parent.
"Project POM" contains project-wide definitions: Java compiler version, dependency management etc. Parent is company-wide POM. Example :JAXB2 Basics Project. Version is updated with each release.
"Module POMs" on different levels. List individual dependencies (versions of dependencies are inherited from the project POM), add "special" build steps. Example: JAXB Basics.
I saw a similar pattern an other OS projects (like Apache's) as well.
A few more comments:
You may also have the "department POM" or "product POM" depending on the company size and product organization.
Think of POM inheritance pretty much as of OOP inheritance. What would you put into which abstract class so that class hierarchy is stable but dynamic? For instance, it would not make sense to define versions of dependencies in the company-wide POM since versions change too often. On the contrary, defining distribution management in earch of the projects would hurt the DRY principle.

Question about maven

I read some useful posts here on SO about previous maven questions, I'm currently very interested in learning maven(cause I like it and because my boss requires me to). I'm currently reading [this][1] book and I'm working my way trough examples. Its a straightforward book but its has some errors inside(trivial ones), yet for a newbie like me can be hard to spot, once spotted it can be easily fixed. Is there any other book better to understand maven from top to bottom?
Second part of the question is relating an example in this book, maybe a simple explanations would resolve my doubts.
Here is the thing, I made a simple-weather project in java which retrieves the weather conditions from yahoo weather server, given the particular zip code it returns weather information.
Then I made an 'simple-webapp'(with maven as well as the one above I forgot to mention that), which is basicaly a web project which has some default servlet already there with maven and it does nothing.
And I have some parent-project I wanna merge those two projects into one, so I made a pom.xml which has 2 modules , 1 to retrieve info(java project) and other to display it on the web (web app).
I made everything work at the end, but here is the odd thing .. if I make webapp display any string "name" lets say then build it independently, it does exactly print that string. But when I put the webapp in the "parent-project" and change this string to "name1" and build it as sa partent-project sub module.. nothing changes ..
So I go back to the point, because simple-webapp is dependent on simple-weather I can't build it anymore on its own, so now if I wanna make some changes to the webapp.. modify the webapp outside the "parent-project" build it there then paste it back to the parent-project and then the changes will apply, why is that, why can't I directly change the servlet content/or add another one in the webapp as the part of the "parent-project"?
Thank you.. I know its a long and boring question, but I'm just trying to learn things and there is no better place to ask than here :D
EDIT - HERE ARE POM FILES FOR EACH PROJECT :
1. simple-parent pom.xml
<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
http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.sonatype.mavenbook.multi</groupId>
<artifactId>simple-parent</artifactId>
<packaging>pom</packaging>
<version>1.0</version>
<name>Multi Chapter Simple Parent Project</name>
<modules>
<module>simple-weather</module>
<module>simple-webapp</module>
</modules>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
2. simple-weather pom.xml
<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
http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.sonatype.mavenbook.multi</groupId>
<artifactId>simple-parent</artifactId>
<version>1.0</version>
</parent>
<artifactId>simple-weather</artifactId>
<packaging>jar</packaging>
<name>Multi Chapter Simple Weather API</name>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<configuration>
<testFailureIgnore>true</testFailureIgnore>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
<dependencies>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.14</version>
</dependency>
<dependency>
<groupId>dom4j</groupId>
<artifactId>dom4j</artifactId>
<version>1.6.1</version>
</dependency>
<dependency>
<groupId>jaxen</groupId>
<artifactId>jaxen</artifactId>
<version>1.1.1</version>
</dependency>
<dependency>
<groupId>velocity</groupId>
<artifactId>velocity</artifactId>
<version>1.5</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-io</artifactId>
<version>1.3.2</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
3. simple-webapp pom.xml
<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
http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.sonatype.mavenbook.multi</groupId>
<artifactId>simple-parent</artifactId>
<version>1.0</version>
</parent>
<artifactId>simple-webapp</artifactId>
<packaging>war</packaging>
<name>simple-webapp Maven Webapp</name>
<dependencies>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.4</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.sonatype.mavenbook.multi</groupId>
<artifactId>simple-weather</artifactId>
<version>1.0</version>
</dependency>
</dependencies>
<build>
<finalName>simple-webapp</finalName>
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

I am not sure to completely understand your question. However, let's explain some principles in Maven.
So you have such a structure:
parent
+ simple-weather
+ simple-webapp
On a Maven point of view, we have 3 projects here:
parent, which is a pom project (i.e. its packaging attribute is set to pom)
simple-weather, which is a jar project and has parent as parent.
simple-webapp, which is a war project, has parent as parent and simple-weather as dependency.
The parent projects uses two concepts in Maven:
The inheritance, which say that all of his children (simple-weather and simple-webapp) will inherit all of his properties (this concept is almost the same thing as the extends in Java).
The aggregation, which is defined by the definition of <modules>. Aggregation means that every command that will be run on the project will also be run on each module.
What happen if I build (using mvn clean install) on the parent directory?
Maven will "compile" the parent project and then install the pom.xml in the local repository.
Maven will compile the simple-weather project, but as it has a parent, Maven will look the parent pom.xml file into the local repository. Once the JAR is created, it is installed in the local repository.
Maven will finally compile the simple-webapp project. Maven will do the same thing for the parent pom.xml, but also for the simple-weather project.
The situtation explained in the 3rd point is important: If you want to build the simple-webapp project, Maven will always try to find all of his dependencies - including simple-weather - from the local (or distant) repository.
That's why if you build only the simple-webapp without building and installing simple-weather, Maven will not find the latter project, or will find an older version.
So to summarize, when you work on multi-modules project with Maven, try to always run the build and install commands from the root (or parent) directory.
I hope that this explanation is clear enough and help you to understand what happen in your case. Do not hesitate to ask more information...