DevOps Classroom Series – 30/Nov/2021 – Direct DevOps from Quality Thought

Maven

Maven provides java and java based languages developers a way to managed
- Builds
- Documentations
- Dependencies
- Releases
- Distributions

Convention over Configuration:

Maven uses Convention over configuration & developers are not required to creat the build process themselves

Item	Default
Source Code	${basedir}/src/main/java
Resources	${basedir}/src/main/resources
Tests	${basedir}/src/test
Compiled byte code	${basedir}/target/classes
Distributable (jar/war/ear)	${basedir}/target
POM	${basedir}/pom.xml

Installing Maven:
- Pre-reqs:
  - Java with 1.7 or above (Verify if the JAVA is installed java -version)
- To install Maven
  - Package managers => apt, yum, brew (mac), choco(windows)
  - Manual process => download tar/zip file depending on your OS Refer Here and configure everything on your own
- Manual installation steps
  - Install suitable version of java sudo apt update && sudo apt install openjdk-11-jdk -y
  - Set Java Environment: Set JAVA_HOME environment variable
    - on ubuntu instances => /usr/lib/jvm/java-11-openjdk-amd64
    - on redhat/centos instances => /usr/lib/jvm/jre
    - We need to create enviornment varaible export JAVA_HOME=<Java Path>
    - Open the file ~/.bashrc and add export statement at the last
    - Try to logout and login or source ~/.bashrc
  - Download the maven and extract it to /usr/local
```
cd /tmp
wget https://dlcdn.apache.org/maven/maven-3/3.8.4/binaries/apache-maven-3.8.4-bin.tar.gz
tar -xvzf apache-maven-3.8.4-bin.tar.gz
sudo cp -r apache-maven-3.8.4/ /usr/local
```
  - Now we need to add two environment variables
    - M2_HOME => This represent the maven directory
    - PATH => Add the path to maven binary
  - Note: The configuration which we have done is for the particular user, if you want the same configuration for all users try adding export statements to /etc/enviornment

Maven- POM (Project Object Model)

This is fundamental unit of work in Maven which is an xml file that resides in projects base directory
There should be a single pom.xml file for every project.
- All pom files require the project elements and three mandatory fields
  - groupId
  - artifactId
  - version
- Projects notation is groupId:artifiactId:version
Minimal Elements of POM
- Project root: This is schema setting for the maven project
- Model version: model version of maven and it is always 4.0.0
- groupId: This is an id of project’s group. Generally organziation name
- artifactId: This is Id of the project. Generally name of the project
- version: version of the project. If the Version Contains SNAPSHOT understanding is project version is still under development. If it doesn’t contain it is expected to be Ready for Release, some organization use RELEASE in version to represent the release.
Super POM:
- This is Maven’s default POM. All the POMs inherit from a parent or default
Goals: A Build lifecycle is a well defined sequence of phases, in which the goals are execute

Phase	Comments
prepare-resources	Resource copying can be customized in this phase
validate	Validates if the project & other info is available or not
compile	Source code is compile and if there are errors they would be shown
test	executes all the tests written in test folder
package	This generates jar/war package
install	This phase installs the pom and package in local repository
deploy	Copies the final package to remote repository
clean	clean will remove the target folder
site	which creates the documentation

All goals of maven

validate, initialize, generate-sources, process-sources, generate-resources, process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy, pre-clean, clean, post-clean, pre-site, site, post-site, site-deploy

Activities

Sample1 : Refer Here for the git repository
Refer Here for the initial set of changes
Lets generate Super POM mvn help:effective-pom

<?xml version="1.0" encoding="UTF-8"?>
<!-- ====================================================================== -->
<!--                                                                        -->
<!-- Generated by Maven Help Plugin on 2021-11-30T03:11:26Z                 -->
<!-- See: http://maven.apache.org/plugins/maven-help-plugin/                -->
<!--                                                                        -->
<!-- ====================================================================== -->
<!-- ====================================================================== -->
<!--                                                                        -->
<!-- Effective POM for project 'com.qt.devops:sample1-app:jar:1.0-SNAPSHOT' -->
<!--                                                                        -->
<!-- ====================================================================== -->
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.qt.devops</groupId>
  <artifactId>sample1-app</artifactId>
  <version>1.0-SNAPSHOT</version>
  <properties>
    <maven.compiler.source>11</maven.compiler.source>
    <maven.compiler.target>11</maven.compiler.target>
  </properties>
  <repositories>
    <repository>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
    </repository>
  </repositories>
  <pluginRepositories>
    <pluginRepository>
      <releases>
        <updatePolicy>never</updatePolicy>
      </releases>
      <snapshots>
        <enabled>false</enabled>
      </snapshots>
      <id>central</id>
      <name>Central Repository</name>
      <url>https://repo.maven.apache.org/maven2</url>
    </pluginRepository>
  </pluginRepositories>
  <build>
    <sourceDirectory>/home/qtdevops/mavenexamples/sample1/src/main/java</sourceDirectory>
    <scriptSourceDirectory>/home/qtdevops/mavenexamples/sample1/src/main/scripts</scriptSourceDirectory>
    <testSourceDirectory>/home/qtdevops/mavenexamples/sample1/src/test/java</testSourceDirectory>
    <outputDirectory>/home/qtdevops/mavenexamples/sample1/target/classes</outputDirectory>
    <testOutputDirectory>/home/qtdevops/mavenexamples/sample1/target/test-classes</testOutputDirectory>
    <resources>
      <resource>
        <directory>/home/qtdevops/mavenexamples/sample1/src/main/resources</directory>
      </resource>
    </resources>
    <testResources>
      <testResource>
        <directory>/home/qtdevops/mavenexamples/sample1/src/test/resources</directory>
      </testResource>
    </testResources>
    <directory>/home/qtdevops/mavenexamples/sample1/target</directory>
    <finalName>sample1-app-1.0-SNAPSHOT</finalName>
    <pluginManagement>
      <plugins>
        <plugin>
          <artifactId>maven-antrun-plugin</artifactId>
          <version>1.3</version>
        </plugin>
        <plugin>
          <artifactId>maven-assembly-plugin</artifactId>
          <version>2.2-beta-5</version>
        </plugin>
        <plugin>
          <artifactId>maven-dependency-plugin</artifactId>
          <version>2.8</version>
        </plugin>
        <plugin>
          <artifactId>maven-release-plugin</artifactId>
          <version>2.5.3</version>
        </plugin>
      </plugins>
    </pluginManagement>
    <plugins>
      <plugin>
        <artifactId>maven-clean-plugin</artifactId>
        <version>2.5</version>
        <executions>
          <execution>
            <id>default-clean</id>
            <phase>clean</phase>
            <goals>
              <goal>clean</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-resources-plugin</artifactId>
        <version>2.6</version>
        <executions>
          <execution>
            <id>default-testResources</id>
            <phase>process-test-resources</phase>
            <goals>
              <goal>testResources</goal>
            </goals>
          </execution>
          <execution>
            <id>default-resources</id>
            <phase>process-resources</phase>
            <goals>
              <goal>resources</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-jar-plugin</artifactId>
        <version>2.4</version>
        <executions>
          <execution>
            <id>default-jar</id>
            <phase>package</phase>
            <goals>
              <goal>jar</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.1</version>
        <executions>
          <execution>
            <id>default-compile</id>
            <phase>compile</phase>
            <goals>
              <goal>compile</goal>
            </goals>
          </execution>
          <execution>
            <id>default-testCompile</id>
            <phase>test-compile</phase>
            <goals>
              <goal>testCompile</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.12.4</version>
        <executions>
          <execution>
            <id>default-test</id>
            <phase>test</phase>
            <goals>
              <goal>test</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-install-plugin</artifactId>
        <version>2.4</version>
        <executions>
          <execution>
            <id>default-install</id>
            <phase>install</phase>
            <goals>
              <goal>install</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-deploy-plugin</artifactId>
        <version>2.7</version>
        <executions>
          <execution>
            <id>default-deploy</id>
            <phase>deploy</phase>
            <goals>
              <goal>deploy</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      <plugin>
        <artifactId>maven-site-plugin</artifactId>
        <version>3.3</version>
        <executions>
          <execution>
            <id>default-site</id>
            <phase>site</phase>
            <goals>
              <goal>site</goal>
            </goals>
            <configuration>
              <outputDirectory>/home/qtdevops/mavenexamples/sample1/target/site</outputDirectory>
              <reportPlugins>
                <reportPlugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-project-info-reports-plugin</artifactId>
                </reportPlugin>
              </reportPlugins>
            </configuration>
          </execution>
          <execution>
            <id>default-deploy</id>
            <phase>site-deploy</phase>
            <goals>
              <goal>deploy</goal>
            </goals>
            <configuration>
              <outputDirectory>/home/qtdevops/mavenexamples/sample1/target/site</outputDirectory>
              <reportPlugins>
                <reportPlugin>
                  <groupId>org.apache.maven.plugins</groupId>
                  <artifactId>maven-project-info-reports-plugin</artifactId>
                </reportPlugin>
              </reportPlugins>
            </configuration>
          </execution>
        </executions>
        <configuration>
          <outputDirectory>/home/qtdevops/mavenexamples/sample1/target/site</outputDirectory>
          <reportPlugins>
            <reportPlugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-project-info-reports-plugin</artifactId>
            </reportPlugin>
          </reportPlugins>
        </configuration>
      </plugin>
    </plugins>
  </build>
  <reporting>
    <outputDirectory>/home/qtdevops/mavenexamples/sample1/target/site</outputDirectory>
  </reporting>
</project>

Now execute mvn compile
Now execute mvn package
Now execute mvn clean
We can combine goals and also run

mvn clean compile

Now lets build some opensource project using maven Refer Here

DevOps Classroom Series – 30/Nov/2021

Maven

Maven- POM (Project Object Model)

Activities

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Maven

Maven- POM (Project Object Model)

Activities

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