Purpose

To give a brief overview about Maven and detail its most important components.

What is Maven?

Build Tool

• gives an artifact as an output (component, jar, zip)
• manages dependencies

Project Management

• versioning
• Meta information about the project
• produces Javadocs/site info

Folder Structure

• looks for source code in src/main/java
• compiles all code into target
• using the pom.xml file (also add the special plugin needed to make sure it works for Java 10+)
• everything goes by //

src/main/java

• where all Java code is stored
• package declaration starts from here
• for other languages, src/main/resources or src/main/groovy or something like that is used.

src/test/java

• for all test code
• specifically for unit tests
• automated tests

target

• compilation directory
• tests
• artifacts

pom.xml

• groupId: same as the package. They designate the business/application name as web address
• artifactId: name of the application and the artifact.
• version: snapshot v/s release
• packaging: how to distribute the application. default - jar
• dependencies:
  • imported by naming convention
  • groupId, artifactId, version has to be known
  • once specified in the dependencies section, any transitive ones are automatically pulled in

Scopes

• compile: default, all resources are available everywhere inside the application
• provided: like compile, the artifact is available throughout the build cycle but it is not included in the final artifact. Eg: Servlet APIs, XML APIs
• runtime: not needed during compilation but during execution, like a driver that gets loaded at runtime. Eg: JDBC, JARs
• test: only during testing compilation and execution phase. nothing for compilation, packaging, or execution
• system: very brittle, not to be used
• import: deals with dependency mgmt, sharing resources across multiple POMs.

Repositories:

• HTTP accessible location to download files from
• default location (repo.maven.apache.org) defined in the Super POM inside the Maven installation which should be edited as overriding can be done in other ways as well.
• looks in local first, else pulls from remote
• local maven repo is in ~/.m2
• default storage location is /m2/groupId/artifactId
• Corporate Repo - Nexus, Artifactory
• Dependency Repo
• Plugin Repo

Plugins:

used to build & package applications

Phases:

• validate: validate project source & structure
• compile: compile source code
• test: compile test course code
• package: packages code in the defined packaging
• integration-test: deploy and run integration tests
• verify: runs checks to verify integrity
• install: install and package to local repo
• deploy: same as install but to remote repo

Different Plugins:

Compile:

• used to compile source & test code (in different phases)
• invokes Javac
• builds classpath based on dependencies & scope specified
• defaults to older versions of Java

Jar:

• packages code to a Jar file
• package phase
• include & exclude files
• builds manifest

Source:

• package source code to distribute for context-sensitive help
• make code-intensive javadoc
• package phase

Javadoc:

• package javadocs to our source code
• package phase
• tied to a Maven site goal

TODO:

• Add installation instructions
• Add examples -> files, screenshots
• Link projects
• Research tips & tricks