1st Program in Maven @ Ubuntu

Maven

What is Maven?

It is a

Build tool – building a code in a development environment

Project management tool – it helps to generate reports, helps in the dependency management, etc.

Maven as a Build tool.

Why we are using Maven?

To reduce the common problems and activities which are needed, when we are developing applications.

1. Multiple jars – Program may contain one/many frameworks and frameworks are need to include it all the required “jar”. “jar” are need to available in compile time, need to bundle them in the distribution. (We can miss something/ we don’t know what is jar?)

2. Dependencies and versions – a jar can depend on another jar, so we have need to make sure that all my dependencies are closed and make sure that I have supplied all the dependencies. Dependencies could differ bases on the versions.

3. Project structure – Proper structure for the application. (E.g. Directories, libraries , etc.)

4. Building, publishing and deploying

Repositories – helps Maven to overcome the above mention common problem and activities.

How to install Maven? Click Here.

Make a Simple Maven Application.

Steps:

1. Make a directory [mkdir myapp]

2. Move into the directory [cd myapp/]

3. To download Maven Repositories from online [mvn archetype:generate]

Note – Make sure that you are connected to internet

//this command will download all the Maven plugging.

Choose a number ? Go with the default number what is it showing. (press enter)

What is archetype? It is a model how we want our project. (predefined)

Choose a version number? 6 & enter

Define value for property ‘groupId’? org.apache.maven //similar to the Package

Define value for property ‘artifactId’? MavenSampleApp //similar to class name – name for the complete application

Define value for property ‘version’: 1.0.SNAPSHOT? Use as it as default NOW

Define value for property ‘package’: org.apache.maven:? Use the default selected GroupId

Ask conformation for the inputs what we did now. Press ‘y’ and enter.

FINISHED

It will create a directory named ‘MavenSampleApp’ as we created. And inside to that directory there is a ‘src’ directory and a ‘pom.xml’ file.

Example: Information about the application - ‘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>org.apache.maven</groupId>                 //entries we have entered//

  <artifactId>MavenSampleApp</artifactId>            //entries we have entered//

  <version>1.0-SNAPSHOT</version>                     //entries we have entered//

  <packaging>jar</packaging>                                  //entries we have entered// application we are writing will be build and package as a jar.

  <name>MavenSampleApp</name>             //name of the application. Differ from artifactId. (Application call by this name but saving this compiled application in the repository artifactId will be use) //

  <url>http://maven.apache.org</url>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

  </properties>

  <dependencies>                                //this the place where Maven going to play

    <dependency>

      <groupId>junit</groupId>           //this project is depend on the junit

      <artifactId>junit</artifactId>

      <version>3.8.1</version> //junit version

      <scope>test</scope>

    </dependency>

  </dependencies>

</project>

Compile the Maven Application

Default: There will be a Java class with Main Method having the out put of “Hello World” (selected archetype – create this automatically)

Steps

1. Go to the directory which has ‘pom.xml’

2. [mvn compile]

//downloading all the relative dependencies mentioned in the ‘pom.xml’ + compile the Java class in the application directory. (all the classes in the ‘src’ folder compiled in a single command)

3. [mvn package]

//it will package into a jar file + some downloads of plugging 

After this done you can see a build jar inside the ‘target’ directory which is inside our applicatio directory.

Example: [INFO] Building jar: /home/benjamineubuntu/myapp/MavenSampleApp/target/MavenSampleApp-1.0-SNAPSHOT.jar

4. Execution [java -cp target/MavenSampleApp-1.0-SNAPSHOT.jar org.apache.maven.APP]

Note : Make sure you are inside the directory where the ‘pom.xml’ file is saved.

//java -cp target/MavenSampleApp-1.0-SNAPSHOT.jar [artifactId][.][Java class wants to run (without ‘.java’)]

5. Display output as ‘Hello World!’

What maven has done up to that?

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