Setting up a maven build

Introduction

Based on the concept of a project object model (POM), Maven can manage a project’s build, reporting and documentation from a central piece of information. Default project structure for maven build is given below.

The setup for Maven Build can be done from Eclipse or command prompt. Below are the core elements for the Maven build

settings.xml

In this file you can define your local repository, proxy, JDK version etc. You can place your settings.xml file into %maven_home%/conf/ path.

Please note: If you do not define your localRepository in the settings.xml file then default repository would be %USER_HOME%/.m2/repository

pom.xml

pom.xml file is the heart of maven build. It should be placed under the project folder. This file will be discussed in more details.

Maven Setup

Maven setup in windows

• Download maven zip from official site
• Unzip at some location
• Add M2_HOME environment variable with the PATH_TO_MAVEN_UNZIP_FOLDER

• Update PATH variable with Maven path (PATH=MAVEN_UNZIPPED_FOLDER\bin;%PATH%)

• Verify if installation is successful

Check if maven plugin is available in your eclipse

Normally maven comes with eclipse IDE for J2EE. To check, follow the below steps

• Open eclipse
• Go to Windows->Preference
• Check for Maven entry in the left hand side

If maven plugin is not there in your eclipse then follow the below steps to install the plugin in Eclipse

• Help->Install new software
• Click Add button at top right corner
• At pop up: fill up Name as “MavenPlugin” and Location as http://download.eclipse.org/technology/m2e/releases
• Now click OK
• Once installed then restart the eclipse and check if maven plugin is available in your eclipse

Check setting.xml file

The default location for the settings.xml is ${user.home}/.m2/settings.xml. However, user can change this location in eclipse/cmd prompt. Changing in eclipse is very easy.

• from eclipse: Go to Windows->Preference->Maven->User Settings and mention

• from cmd prompt: settigns.xml should be at {M2_HOME}\conf\setting.xml

Repository

The default repository location is ${user.home}/.m2/repository. However, user can change this in settings.xml file as shown below

<localRepository>path\to\repository</localRepository>

Internet connection

The maven must connect to the internet (or copy the working repository then internet connection is not required) for the first time. To connect to the internet: make sure the proxy tag is correct in your settings.xml

<proxy>
      <id>optional</id>
      <active>true</active>
      <protocol>http</protocol>
      <username>proxyuser</username>
      <password>proxypass</password>
      <host>proxy.host.net</host>
      <port>80</port>
      <nonProxyHosts>local.net|some.host.com</nonProxyHosts>
</proxy>

Mention the maven repository in pom.xml

In pom.xml, if repository is not mentioned then by default then it will look into local repository. If not found then it will look into maven central repository (i.e. http://repo1.maven.org/maven2/). If not found then it will look for the maven remote repository. Below remote repository configuration is required in pom.xml

<repositories>
	<repository>
	    <id>java.net</id>
	    <url>https://maven.java.net/content/repositories/public/</url>
	</repository>
</repositories>

Create a maven project

Create Maven project from Eclipse

• Create a normal project in eclipse
• Right click on the project -> Configure -> Configure to Maven project

Create Maven project from cmd prompt

• Create a project folder
• Then execute the following

mvn archetype:create 
-DgroupId=com.test 
-DartifactId=ArtifactName

Build Java project

In this example, we are going to create an executable jar, place it into another location Follow comments added in each steps in pom.xml file. I have tried to cover all possible scenarios in my pom.xml to create an executable Jar file.

• It defines the dependencies (jars) and their scope.
  • If the scope is system then it picks the jar from the hardcoded location
  • If the scope is test then the testing files does not get copied into the final jar
• Define the JDK version
• Copy resource files (e.g. .properties or .bat) into required folder
• Copy dependant jar files into ${outputPath}/lib folder
• Create executable jar with depandant jars as entry into manifest.mf file
• Copy the jar into final destination
• Also declare variables which are used across the pom.xml

For details, check this pom.xml file

Call ant build from maven script

If you are using JDK1.4 or below then maven does not offer much plugings. So to achieve something you may need to run ant target or ant scripts from maven. This file shows how to call ant script from maven build.

Common issues during maven setup