Building Java Code with Maven

• Maven is a software project management tool (build, dependency management tool)
• This is based on the concept of project object model (POM)
• Maven provides
  • build
  • test
  • reports
  • documentation
  • releases
• Maven follows convention over configuration

Item	Default
source code	${basedir}/src/main/java
Resources	${basedir}/src/main/resources
Tests	${basedir}/src/test
Compile byte code	${basedir}/target/classes
distributable (jar/war)	${basedir}/target

Installing Maven

• Ensure java is installed

#ubuntu
sudo apt update
sudo apt install openjdk-11-jdk -y

• Maven can be downloaded and installed manually Refer Here
• Now lets use apt

sudo apt install maven -y
mvn --version

* Now lets try to install maven using tar file

cd /tmp
wget https://dlcdn.apache.org/maven/maven-3/3.8.5/binaries/apache-maven-3.8.5-bin.tar.gz
tar -xvzf  apache-maven-3.8.5-bin.tar.gz
sudo mv apache-maven-3.8.5 /opt/

• set the following environmental variables in /etc/profile.d/java.sh

export M2_HOME='/opt/apache-maven-3.8.5'
PATH="$M2_HOME/bin:$PATH"
export PATH

• Logout & Login

mvn --version

• The developers will create the pom.xml file, but we need to understand
• When building the java project,
  • compile the code
  • run the unit tests
  • create a package
• In Maven we have goals/build phase
  • compile => Creates .class files
  • test => runs the unit tests and generates the reports. This will also try to compile
  • package => creates the jar/war file. This will execute compile + test
  • install
  • deploy
  • clean => remove the target folder
• Maven dowloads the dependencies by default from internet Refer Here
• Lets compile the spring petclinic
  
• Maven when it downloads the dependencies, uses the folder in ${HOME-DIR}\.m2
• We can combine goals

mvn clean package
mvn compile test package

• Exercise: Make the jenkins build any java project using mvn package