DevOps Classroom Series – 11/Feb/2021

Building/Packaging the Code

• In this series lets try to understand how to build java code
• Building java code is executing the .java files with javac <pathto.java> and then it creates .class file. Now to execute code java <pathto.class>
• In a enterprise software project, we will have multiple java files, so building each file to generate .class file and then combining .class files to build a jar file format is difficult
• Apache ANT was the first famous tool which helped in building java code.
• ANT build files are written in XML format.
• Binary is the format that is packaged version of the code. It can be .exe file, .jar file, .dll file.
• Lets install ant
  • Windows choco install ant
  • Linux Refer Here
• Create a build.xml file in the source code and write build steps in xml file

<?xml version="1.0"?>
<project name="Hello World" default="info">
    <target name="info">
        <echo>Hello world - Welcome to Ant</echo>
    </target>
</project>

• Now navigate to the folder in terminal where you have build.xml file and execute ant

• Refer Here for the sample ant build.xml and steps

• When we write code we use lot of external libraries which is referred as dependency. Generally for any enterprise project build includes managing dependencies.

Apache Maven

• This is a software project managment and comprehension tool Refer Here

• Maven is a tool which follows Convention over configuration

• Some of the conventions are (${basedir} is the folder where you have your project)

  • source code => ${basedir}/src/main/java
  • resources => ${basedir}/src/main/resources
  • Test cases => ${basedir}/src/test
  • Class file => ${basedir}/target/classes
  • Jar/War => ${basedir}/target/

• Installing maven

  • Windows: choco install maven
  • Linux: Refer Here
    • Ubuntu:

    sudo apt update
    sudo apt install openjdk-8-jdk -y
    sudo apt install maven -y
    

    
    • centos:

    sudo yum install java-1.8.0-openjdk -y
    wget https://mirrors.estointernet.in/apache/maven/maven-3/3.6.3/binaries/apache-maven-3.6.3-bin.tar.gz
    tar xzvf apache-maven-3.6.3-bin.tar.gz
    sudo cp -r apache-maven-3.6.3 /opt
    # sudo vi /etc/environment
    export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.275.b01-1.el8_3.x86_64/jre/
    export PATH=$PATH:/opt/apache-maven-3.6.3/bin
    

  • mac: brew install maven

• In Maven we create a pom.xml file where POM stands for Project Object Model. So our sample 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.qualitythought.devops</groupId>
    <artifactId>helloworld</artifactId>
    <version>1.0-SNAPSHOT</version>
</project>

• Now lets move to the root folder of project and execute mvn compile and mvn package