Volatile Memory Fix: Maven

Computer needs to be connected on the internet to use Maven.
To check Maven version:
mvn -- version

To create a project:
Maven will download all required maven programs and prompt for the project type
mvn archetype:generate

Maven will prompt for:

archetype - sample archetype number: (webpapp, restful, ejb, etc)
version - choose the archetrype version:
groupId - similar to package name - ex: com.volatileMemoryFix
artifactID - applicationName - ex: MyMavenTest
versionNumber - leave as default
Maven will create a project / folder called MyMavenTest.
Below is the folder structure:

MyMavenTest
|_pom.xml
|_src
   |_main
|_java
   |_com
|_volatileMemoryFix
   |_App.java
   |_test
        |_java
   |_com
|_volatileMemoryFix
   |_AppTest.java

Checking the pom.xml file:

<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.test.defaultMaven</groupId>
<artifactId>DefaultMavenProject</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>

<name>DefaultMavenProject</name>
<url>http://maven.apache.org</url>

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

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
</dependencies>
</project>

This project depends on jUnit (default dependency)and Maven will take care of all the dependencies (download all the necessary jars)

To compile this project (java classes)

cd MyMavenTest
mvn compile

(Maven will download all the dependencies mentioned in pom.xml and compile all the java class. It will take longer in the first time, given Maven will download all the necessary libraries)

To package the application in a jar file:

mvn package

mvn package will also run all the test cases.

Maven Build

Maven has a build life cycle: (not comprehensive list). The subsequent phase will invoque the previous phases

validade (check if everything is in order (configuration, there is a pom.xml, etc)
compile (download all the jars, it creates a target folder)
test (all the tests will be executed)
package (create a .jar for the application
install (package artifacts in a local Maven repository / publish your jars in local repository)
deploy (publish artifacts to remote repository)

Maven Dependencies

mvn clean delete all the dependencies downloaded previously

Adding a dependency:

Search for "maven repository search" or go to http://mvnrepository.com
Searching for Slf4j (Logger library) . Click on the desired version and copy the following Maven tags into the <dependencies> session of the pom.xml file:

<dependency>
    <groupId>org.grlea.log.adapters</groupId>
    <artifactId>simple-log-sl4j</artifactId>
    <version>1.7</version>
</dependency>


<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.grlea.log.adapters</groupId>
      <artifactId>simple-log-sl4j</artifactId>
      <version>1.7</version>
    </dependency>
</dependencies>

Running mvn compile will download all the jars that belong to the Logger library:

Web Application using Maven

Run mvn archetype:generate
Choose: 448: remote -> org.codehaus.mojo.archetypes:webapp-j2ee14 (-)
Choose the version: default
Choose the 'groupId': com.volatileMemoryFix
Chose the 'artifactId': myWebj2ee14
'version' and 'package' can get their default values
Confirm all the properties configuration.

This is the pom.xml file generated for this project:

<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.volatileMemoryFix</groupId>
<artifactId>myWebj2ee14</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging> 

<name>myWebj2ee14</name>
<url>http://maven.apache.org</url>

<dependencies>
    
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>2.4</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.1</version>
      <scope>provided</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
       
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>2.0.2</version>
        <configuration>
          <source>1.4</source>
          <target>1.4</target>
        </configuration>
      </plugin>
    </plugins>
</build>
</project>

Running mvn compile will download all the dependencies mentioned in pom.xml file.

Running mvn package will create a .war file that can be deployed in a container (tomcat)

This is the package structure:

Maven Plugins

Plugins - extended functionality for Maven. - Maven has a modular architecture.

<plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>2.0.2</version>

        <configuration>
          <source>1.4</source>
          <target>1.4</target>
        </configuration>
      </plugin>
    </plugins>

In order to use Generics, it will be necessary to change the source and target versions to 1.5.

Jetty Plugin

Add the following plugin to pom.xml

<build>
    <plugins>
      <plugin>
        <groupId>org.mortbay.jetty</groupId>
        <artifactId>jetty</artifactId>
        <version>6.1.26</version>
      </plugin>
   .....
   .....
    </plugins>
</build>

Run the following command:

mvn jetty:run (plugin that will handle the command:command)

Eclipse Plugin for Maven

mvn eclipse:eclipse

.classpath and .project files will be created

In eclipse, just open myWebj2ee14 as an existing project and point to the root folder.

Right-click in the project myWebj2ee14, choose "Properties" and verify the M2_REPO Library is configured properly

Install "M2Eclipse" plugin

Run Maven comands :
Right click on pom.xml and run the required commands.
Search for dependencies / artifacts from the IDE:

Creating a new project in Eclipse

Right Click-> Other -> Maven ->New Project->Maven-> Choose / filter the archetypes to create the project from

Running jetty from eclipse

Right click Run as -> Maven build

Monday, April 1, 2013

Maven