¿Puede un proyecto Java tener varios módulos?

Can a Java project have multiple modules?

In a standard multi-module Maven project, we add one or more child Maven modules by placing them under the project’s root folder and declaring them in the parent POM, within the section.

The mechanism in Maven that handles multi-module projects is referred to as the reactor. This part of the Maven core does the following: Collects all the available modules to build. Sorts the projects into the correct build order.

A Project Object Model or POM is the fundamental unit of work in Maven. It is an XML file that contains information about the project and configuration details used by Maven to build the project. Other information such as the project version, description, developers, mailing lists and such can also be specified.

Maven does not support multiple inheritance and a project can have only one parent. The parent project can have its own hierarchy. Maven does not support multiple inheritance and a project can have only one parent.

The mechanism in Maven that handles multi-module projects is referred to as the reactor. This part of the Maven core does the following: Because modules within a multi-module build can depend on each other, it is important that the reactor sorts all the projects in a way that guarantees any project is built before it is required.

Note: When you specify a project with the -am option, Maven will build all of the projects that the specified project depends upon (either directly or indirectly). Maven will examine the list of projects and walk down the dependency tree, finding all of the projects that it needs to build.

Remove elements in the list to build only the modules you please. EDIT: as blackbuild pointed out, as of Maven 3.2.1 you have a new -el flag that excludes projects from the reactor, similarly to what -pl does: The notion of multi-module projects is there to service the needs of codependent segments of a project.

It will automatically build those projects and nothing else. Maven absolutely was designed for this type of dependency. mvn package won’t install anything in your local repository it just packages the project and leaves it in the target folder.

A Spring Boot project that contains nested maven projects is called the multi-module project. In the multi-module project, the parent project works as a container for base maven configurations. In other words, a multi-module project is built from a parent pom that manages a group of submodules.

Spring Boot is a project that is built on the top of the Spring Framework. It provides an easier and faster way to set up, configure, and run both simple and web-based applications. It is a Spring module that provides the RAD (Rapid Application Development) feature to the Spring Framework.

Besides, in the real world, projects may need certain Maven plugins to perform various operations during build lifecycle, share dependencies and profiles or include other BOM projects. Therefore, when leveraging multi-modules, we can build our application’s modules in a single command and if the order matters, Maven will figure this out for us.

Step 1: Create a Maven Project with the name spring-boot-multimodule. Step 2: Open the pom.xml (parent pom) file and change the packaging type jar to pom.

The packaging pom refers to other Maven projects. Splitting the project into multiple modules is useful and easy to maintain. We can also easily edit or remove modules in the project without affecting the other modules. It is useful when we required to deploy modules individually.

The userdaomodule Maven Module Next, let’s define the Maven module that holds an implementation of the Dao interface. Under the project’s root directory, let’s create the userdaomodule/src/main/java/com/baeldung/userdao directory structure, and add to it the following UserDao class: