Having a maven project build its own dependencies?

Question

With maven is it possible to have a top-level project who's packaging type is "war" which will build itself and all of its dependent modules (packaged as jar) and have the build generate a project.war file?

Much of the documentation examples and other examples I've seen often use a top-level project with packaging type of "pom" and the project only serves the purpose of tying the modules together. Can I avoid this?

So basically I need something which is effectively like declaring a <module>my-module</module> for maven to build, and in that same POM, declaring a <dependency>...my-module's artifact...</dependency> on that same module which needs to be built. Maybe a plugin as someone already suggested?

Update: In other words (to simplify the problem): If I have project A and project B, where project A depends on project B - is there a way for me to execute a build on project A and also have it automatically build project B (and include project B as its dependency - creating projectA.war which contains projectB.jar)?

Answer 1

super_aardvark suggested correct way but,
For requirement I would suggest following structure It is suitable and good structure also :

Consedering ProjectA as project-webapp , ProjectB as project-core

You can have following structure :

Your Grand Project :

<?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/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.mycompany.project</groupId>
    <artifactId>project</artifactId>
    <version>2.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <name>Project Repository System</name>
    <description>Project Repository System R2</description>

    <modules>
        <module>project-core</module>
        <module>project-webapp</module>
    </modules>
 </project>

Your WebApp Project:

<?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/maven-v4_0_0.xsd">
    <parent>
        <groupId>com.mycompany.project</groupId>
        <artifactId>project</artifactId>
        <version>2.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <artifactId>project-webapp</artifactId>
    <version>2.0-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>Project Web Application</name>
    <description>Project Repository</description>
    <dependency>
            <groupId>com.mycompany.project</groupId>
            <artifactId>project-core</artifactId>
            <version>2.0-SNAPSHOT</version>
     </dependency>

 </project>

Your Core Project:

<project>
    <parent>
        <groupId>com.mycompany.project</groupId>
        <artifactId>project</artifactId>
        <version>2.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>
    <artifactId>project-core</artifactId>
    <version>2.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>Project Core</name>
    <description>ProjectCore</description>

 </project>

Your Directory structure should look like:

-------Grand Parent.pom
  |
  |--------project-webapp
  |                     |
  |                     project-webapp.pom
  | 
  | -------project-core.pom
                        |
                       project-core.pom

From parent pom execute mvn clean install it will build both the web-app and core project

Answer 2

That's not really what a top-level project is for. Your WAR project has dependencies, which are the artifacts (e.g. jars) that will be included in the WAR (in WEB-INF/lib) when you run 'mvn package'. Your WAR project pom can have the top-level project as its parent, but it shouldn't be the parent of its dependencies. You may want to have that top-level project be the parent of both the WAR project and of the JAR projects that are dependencies in the WAR.