Maven Tutorial

1. Maven tutorial provides basic and advanced concepts of apache maven technology. Our maven tutorial is developed for beginners and professionals.
2. Maven is a powerful project management tool that is based on POM (project object model). It is used for projects build, dependency and documentation.
3. It simplifies the build process like ANT. But it is too much advanced than ANT.
4. Current version of Maven is 3.

Understanding the problem without Maven

There are many problems that we face during the project development. They are discussed below:

1) Adding set of Jars in each project: In case of struts, spring, hibernate frameworks, we need to add set of jar files in each project. It must include all the dependencies of jars also.

2) Creating the right project structure: We must create the right project structure in servlet, struts etc, otherwise it will not be executed.

3) Building and Deploying the project: We must have to build and deploy the project so that it may work.

What it does?

Maven simplifies the above mentioned problems. It does mainly following tasks.

1. It makes a project easy to build
2. It provides uniform build process (maven project can be shared by all the maven projects)
3. It provides project information (log document, cross referenced sources, mailing list, dependency list, unit test reports etc.)
4. It is easy to migrate for new features of Maven

Apache Maven helps to manage

• Builds
• Documentation
• Reporing
• SCMs
• Releases
• Distribution

What is Build Tool

A build tool takes care of everything for building a process. It does following:

• Generates source code (if auto-generated code is used)
• Generates documentation from source code
• Compiles source code
• Packages compiled code into JAR of ZIP file
• Installs the packaged code in local repository, server repository, or central repository

Difference between Ant and Maven

Ant and Maven both are build tools provided by Apache. The main purpose of these technologies is to ease the build process of a project.

There are many differences between ant and maven that are given below:

Ant	Maven
Ant doesn't has formal conventions, so we need to provide information of the project structure in build.xml file.	Maven has a convention to place source code, compiled code etc. So we don't need to provide information about the project structure in pom.xml file.
Ant is procedural, you need to provide information about what to do and when to do through code. You need to provide order.	Maven is declarative, everything you define in the pom.xml file.
There is no life cycle in Ant.	There is life cycle in Maven.
It is a tool box.	It is a framework.
It is mainly a build tool.	It is mainly a project management tool.
The ant scripts are not reusable.	The maven plugins are reusable.
It is less preferred than Maven.	It is more preferred than Ant.

Maven Repository

A maven repository is a directory of packaged JAR file with pom.xml file. Maven searches for dependencies in the repositories. There are 3 types of maven repository:

1. Local Repository
2. Central Repository
3. Remote Repository

Maven searches for the dependencies in the following order:

Local repository then Central repository then Remote repository.

If dependency is not found in these repositories, maven stops processing and throws an error.

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Maven Local Repository

Maven local repository is located in your local system. It is created by the maven when you run any maven command.

By default, maven local repository is %USER_HOME%/.m2 directory. For example: C:\Users\SSS IT\.m2.

Maven Central Repository

Maven central repository is located on the web. It has been created by the apache maven community itself.

The path of central repository is: http://repo1.maven.org/maven2/.

The central repository contains a lot of common libraries that can be viewed by this url http://search.maven.org/#browse.

Maven Remote Repository

Maven remote repository is located on the web. Most of libraries can be missing from the central repository such as JBoss library etc, so we need to define remote repository in pom.xml file.

Let's see the code to add the jUnit library in pom.xml file.

pom.xml

<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/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.javatpoint.application1</groupId> <artifactId>my-application1</artifactId> <version>1.0</version> <packaging>jar</packaging> <name>Maven Quick Start Archetype</name> <url>http://maven.apache.org</url> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.8.2</version> <scope>test</scope> </dependency> </dependencies> </project>

You can search any repository from Maven official website mvnrepository.com.

Maven pom.xml file

POM is an acronym for Project Object Model. The pom.xml file contains information of project and configuration information for the maven to build the project such as dependencies, build directory, source directory, test source directory, plugin, goals etc.

Maven reads the pom.xml file, then executes the goal.

Before maven 2, it was named as project.xml file. But, since maven 2 (also in maven 3), it is renamed as pom.xml.

Elements of maven pom.xml file

For creating the simple pom.xml file, you need to have following elements:

Element	Description
project	It is the root element of pom.xml file.
modelVersion	It is the sub element of project. It specifies the modelVersion. It should be set to 4.0.0.
groupId	It is the sub element of project. It specifies the id for the project group.
artifactId	It is the sub element of project. It specifies the id for the artifact (project). An artifact is something that is either produced or used by a project. Examples of artifacts produced by Maven for a project include: JARs, source and binary distributions, and WARs.
version	It is the sub element of project. It specifies the version of the artifact under given group.

File: pom.xml

<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/xsd/maven-4.0.0.xsd">        <modelVersion>4.0.0</modelVersion>     <groupId>com.javatpoint.application1</groupId>     <artifactId>my-app</artifactId>     <version>1</version>      </project>

Maven pom.xml file with additional elements

Here, we are going to add other elements in pom.xml file such as:

Element	Description
packaging	defines packaging type such as jar, war etc.
name	defines name of the maven project.
url	defines url of the project.
dependencies	defines dependencies for this project.
dependency	defines a dependency. It is used inside dependencies.
scope	defines scope for this maven project. It can be compile, provided, runtime, test and system.

File: pom.xml

<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/xsd/maven-4.0.0.xsd">        <modelVersion>4.0.0</modelVersion>        <groupId>com.javatpoint.application1</groupId>     <artifactId>my-application1</artifactId>     <version>1.0</version>     <packaging>jar</packaging>        <name>Maven Quick Start Archetype</name>     <url>http://maven.apache.org</url>        <dependencies>       <dependency>         <groupId>junit</groupId>         <artifactId>junit</artifactId>         <version>4.8.2</version>         <scope>test</scope>       </dependency>     </dependencies>      </project>

Maven Example

We can create a simple maven example by executing the archetype:generate command of mvn tool.

To create a simple java project using maven, you need to open command prompt and run the archetype:generate command of mvn tool.

Syntax

The syntax to generate the project architecture is given below:

mvn archetype:generate -DgroupId=groupid -DartifactId=artifactid    -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=booleanValue

Example

The example to generate the project architecture is given below:

mvn archetype:generate -DgroupId=com.javatpoint -DartifactId=CubeGenerator    -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

Compile the Maven Java Project

To compile the project, go to the project directory,

for example: /home/Ubuntu/CubeGenerator and write the following command on the

command prompt:

mvn clean compile

Now, you will see a lot of execution on the command prompt. If you check your project directory, target directory is created that contains the class files.

Run the Maven Java Project

To run the project, go to the project directory\target\classes,

for example: C:\Users\SSS IT\CubeGenerator\target\classes and write the following

command on the command prompt:

java com.javatpoint.App

Now, you will see the output on the command prompt:

Output of the maven example

Hello World!