Coding Bootcamp: Structure, depend and build

The problems

"I want to structure my project in a way that is independent of the IDE I (or others) use."

"I want to have an easy way to package and deploy my project on Tomcat."

"I want to be able to manage the dependencies of my project in a less messy way."

The tool

Apache Maven is a tool to manage Java
projects.

There are similar tools both for Java and for other programming
languages.

• Gradle
  
• Apache Ant + Apache Ivy
  
• SBT
  
• npm
  
• bower
  
• pip
  
• ...

The projects

Each Maven project has a group ID and an artifact ID.

Group ID: follows package naming rules

E.g. org.afdemp

Artifact ID: contains lowercase letters and no strange symbols

E.g. coding-bootcamp

A project is uniquely identified by the combination of its group
and artifact ID.

The POM

The pom.xml file resides in the root directory of the project.

It is the main (and, in most cases, the only) configuration file for the project.

It is an XML file.

<?xml version="1.0" encoding="UTF-8"?>
<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>org.afdemp</groupId>
  <artifactId>coding-bootcamp</artifactId>
  <version>1.0.0</version>

  <packaging>jar</packaging>

  <name>Coding bootcamp</name>
  <description>The project for the 1st coding bootcamp.</description>
  
  <dependencies>
  ...
  </dependencies>
  
  <build>
  ...
  </build>
  
</project>

The structure

All Maven projects are expected to have the following directory layout.

src/main/java: the application sources

src/main/resources: the application resources

src/main/webapp:the web application sources

src/test/java: the test sources

src/test/resources: the test resources

The dependencies

Dependencies are listed in the <dependencies> element.

Group ID, artifact ID and version must be specified for all dependencies.

<dependencies>
  ...
  <dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.5</version>
  </dependency>
  ...
</dependencies>

The build process

The <build> element contains most build settings.

The final name of the packaged project.

<build>
  ...
  <finalName>coding-bootcamp</finalName>
  ...
</build>

The version of the Java compiler.

<build>
  ...
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.2</version>
      <configuration>
        <source>1.8</source>
        <target>1.8</target>
      </configuration>
    </plugin>
  </plugins>
  ...
</build>

The phases

The build lifecycle is made of phases.

compile: compile the sources

test: run the tests

package: package the compiled code in its distributable format (e.g. JAR)

install: install the package into the local repository

clean: clean up after previous builds

Hello Maven

hello-maven/pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>hellos</groupId>
  <artifactId>hello-maven</artifactId>

  <version>1.0.0</version>

  <name>Hello Maven</name>
  <description>Says hello to Maven.</description>

  <packaging>jar</packaging>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.2</version>
        <configuration>
          <source>1.8</source>
          <target>1.8</target>
        </configuration>
      </plugin>
     </plugins>
  </build>

</project>

Hello Maven

hello-maven/src/main/java/hellos/HelloMaven.java

package hellos;

public class HelloMaven {
  public static void main(String...args) {
    System.out.println("Hello Maven!");
  }
}

Say hello to Maven

$ mvn clean package

$ java -cp target/hello-maven-1.0.0.jar hellos.HelloMaven

Hello Web

pom.xml

?xml version="1.0" encoding="UTF-8"?>
<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/maven-v4_0_0.xsd">

  <modelVersion>4.0.0</modelVersion>

  <groupId>hellos</groupId>
  <artifactId>hello-web</artifactId>

  <version>1.0.0</version>

  <name>Hello Web</name>
  <description>Says hello to the Web.</description>

  <packaging>war</packaging>

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>2.5</version>
    </dependency>
  </dependencies>

  <build>
    <finalName>hello-web</finalName>
  </build>
 
</project>

Hello Web

src/main/webapp/index.html

<html>
  <head>
    <title>Hello Web!</title>
  </head>
  <body>
    <p>Hello Web!</p>
  </body>
</html>

Hello Web

src/main/webapp/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
  </welcome-file-list>
</web-app>   

Say hello to the Web

$ mvn clean package

$ cp target/hello-web.war $CATALINA_HOME/webapps/

$ $CATALINA_HOME/bin/catalina.sh run

Exercise

Write a Java application that receives a number as a command-line
argument, and prints whether that number is prime or not.

Use Apache Maven.

Use Apache Commons Math Library.