Maven Guide

Maven

• Powerful build tool built in Java
• Automates software build tool
• Efficient transitive dependency management
• Builds, Publishes & deploys projects at once

Need for Maven

• Difficult old Tasks(Downloading dependencies, adding further jars in classpath)

Maven vs Ant

• Maven uses declarative approach(What to build & not how to build)
• Ant uses imperative approach(What to build & how to build)

Installation

• Download Maven and set the environment variables as below
• M2_HOME=/usr/local/apache-maven/apache-maven-3.3.9
• M2=$M2_HOME/bin : Helps in accessing CMD line of Maven
• MAVEN_OPTS=-Xms256m -Xmx512m

Maven Working

1. Reads pom.xml(Describes project, manages dependencies & configures plugin for building software)
2. Downloads dependencies from central repo to local repository(C:\Users\anupama.m2\repository)
3. Executes lifecycles, build phases & goals
4. Executes plugin (Executes acccording to selected build profile)

Maven Repository

• Directories of packaged JAR files that contain metadata(POM) based on which dependencies are downloaded
• Types
  1. Local : Local PC
  2. Remote : Any server
  3. Central : Internet(Maven Community)

Identifier Descriptions

• modelVersion : Version of the pom model matching with maven version
• groupId : Project created by
• artifactId : Project name
• version : Semantic version of current release for project
• packaging : JAR/WAR/EAR/ZIP
• repositories : If not found in maven central repository, then url to external repo needs to be given
• properties : Value placeholders used across pom.xml as ${property-name}
• profiles : Describes the environment - dev,test,prod
• build : Describes default maven goal, compiled project directory and application final name

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.anupama.demoproject</groupId>
    <artifactId>demo-project-application</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/>
    </parent>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <repositories>
        <repository>
            <id>JBoss repository</id>
            <url>http://repository.jboss.org/nexus/content/groups/public/</url>
        </repository>
    </repositories>

    <profiles>
        <profile>
            <id>production</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-maven-plugin</artifactId>
                    </plugin>
                </plugins>
            </build>
    </profile>
    
</project>

Effective POM

• Resultant pom can be seen here(POM inheritance and dependencies)

mvn help:effective-pom

Maven Settings File

• Maven Installation Directory

C:\Users\anupa.m2\wrapper\dists\apache-maven-3.6.3-bin\apache-maven-3.6.3\conf\settings.xml

Maven Build Lifecycle : Sequence of build phases which in turn has sequence of goals

• validate: validate the project is correct and all necessary information is available
• compile: compile the source code of the project
• test: test the compiled source code using a suitable unit testing framework. These tests should not require the code be packaged or deployed
• package: take the compiled code and package it in its distributable format, such as a JAR.
• integration-test: process and deploy the package if necessary into an environment where integration tests can be run
• verify: run any checks to verify the package is valid and meets quality criteria
• install: install the package into the local repository, for use as a dependency in other projects locally
• deploy: done in an integration or release environment, copies the final package to the remote repository for sharing with other developers and projects.
• clean: cleans up artifacts created by prior builds
• site: generates site documentation for this project

Build Profiles

• Configurational values required to build project using different configurations for corresponding builds for different environments

Build Plugins

• Group of goals which may or may not be of same phase
• Performs specific goals

Maven Architecture

• Maven -> Reads pom.xml -> Connects with Maven Repository -> Does the task

Build Phases

• Compile -> Test-Compile -> Test -> Package -> Integration-test -> Verify -> Install -> Deploy

Commands

mvn --version mvn archetype:generate

Building JARs

• In progress

References

• https://maven.apache.org/guides/getting-started/maven-in-five-minutes.html
• http://tutorials.jenkov.com/maven/maven-tutorial.html