Maven Tutorial for Beginners in 5 Steps

It is tough to define what Maven accomplishes.

Every day, Developer undertakes a variety of tasks.

Manages Dependencies
- Web Layer (Spring MVC)
- Data Layer (JPA - Hibernate) etc..
Build a jar or a war or an ear
Run the application locally
- Tomcat or Jetty
Deploy to a T environment
Add new dependencies to a project
Run Unit Tests
Generate Projects
Create Eclipse Workspace

All of this and more is made possible by Maven…

Getting Started

Git Repository - https://github.com/in28minutes/getting-started-in-5-steps/tree/master/maven-in-5-steps
Pre-requisites
- Java & Eclipse - https://www.youtube.com/playlist?list=PLBBog2r6uMCSmMVTW_QmDLyASBvovyAO3
We will use embedded maven in Eclipse

Overview

Step 1 : Creating and importing a Maven Project
Step 2 : Understanding Project Object Model - pom.xml
Step 3 : Maven Build Life Cycle
Step 4 : How does Maven Work?
Step 5 : Important Maven Commands

Step 1 : Creating and importing a Maven Project

Creating a Spring Project with Spring Initializr is a cake walk.

Spring Initializr http://start.spring.io/ is great tool to bootstrap your Spring Boot projects.

As shown in the image above, following steps have to be done

Launch Spring Initializr and choose the following
- Choose com.in28minutes.learning.maven as Group
- Choose maven-in-few-steps as Artifact
- Choose Dependency
  - Web
Click Generate Project.
Import the project into Eclipse.
If you want to understand all the files that are part of this project, you can go here.

Step 2 : Understanding the `pom.xml` Project Object Model

Naming a project

How can other projects benefit from our project? Using the groupId and artifactId from our project

	<groupId>com.in28minutes.learning.maven</groupId>
	<artifactId>maven-in-few-steps</artifactId>

Parent Pom

The same as Java Inheritance. We get a lot of things from our parents.

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>3.0.4/version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>

Declaration of Dependencies

Dependencies are frameworks required to construct your project.

In the following example, we will add two 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>

Step 3 : Life Cycle Maven Build

When we execute mvn clean install we finish the whole maven build life cycle.

LifeCycle construction is a series of phases.

Validate
Compile
Test
Package
Integration Test
Verify
Install
Deploy

Maven prefers convention to configuration.

Pre defined folder structure

Source Code
- ${basedir}/src/main/java
- ${basedir}/src/main/resources
Test Code
- ${basedir}/src/test

Step 4 : How does Maven Work?

All jars in the Maven Repository are indexed by artifactid and group id.

When we add a dependence to our pom.xml, maven queries the maven repository for jar dependencies, using the group id and artefact id as input.

Maven repository stores all the versions of all dependencies. JUnit 4.2,4.3,4.4

The jar dependencies are saved on your system in the maven local repository folder. All of our projects would make use of the jars in the maven local repository.

Local Repository: a temporary folder on your workstation in which Maven keeps jar and dependent files obtained from the Maven Repository.

Step 5 : Important Maven Commands

mvn --version
mvn compile (compiles source files)
mvn test-compile (compiles test files) - one thing to observe is this also compiles source files
mvn clean - deletes target directory
mvn test - run unit tests
mvn package - creates the jar
help:effective-settings
help:effective-pom
dependency:tree
dependency:sources
--debug