Building and Running Java SE Application Using Maven

Before You Begin

Purpose

In this tutorial, you create and build a Java Platform, Standard Edition (Java SE) application using Maven. You install, configure, build, and create an executable Java Archive (JAR) file with Maven.

Time to Complete

Approximately 90 minutes

Background

Maven is a build management tool that is central to project build tasks such as compilation, packaging, and artifact management. Maven uses a strict XML-based rule set to promote consistency while maintaining flexibility. Because most Java-centric continuous integration systems integrate well with Maven, it's a good choice for an underlying build system.

The primary goal of Maven is to provide:

A project model that is reusable, maintainable, and easier to comprehend
Plug-ins or tools that interact with the declarative model

The Maven project structure and contents are declared in the pom.xml file. The Project Object Model (POM) is the fundamental unit of the entire Maven system.

Maven contains three types of repositories for storing JARs, plug-ins, and other project-related artifacts:

Local Repository: The location created on your machine when you run your first instance of a Maven command in your machine
Central Repository: The Maven community-owned repository that contains commonly used libraries
Remote Repository: A developer-owned custom repository that contains project-related libraries and JARs

What Do You Need?

Download and install the latest Java SE Development Kit. For this tutorial, the available version is Java SE 8.
Download the Apache Maven. For this tutorial, the available version is 3.2.2.

Setting Up the Maven Environment

In this section, you extract the downloaded archive and install the latest Maven version to a directory of your choice. You verify the Java installation, set the Maven environment, and verify the Maven installation.

Verify the Java installation:

java -version

The output displays the Java version that you installed.
Extract the downloaded Maven x.x.x archive to a local directory.

The archive names are:
- Windows OS: apache-maven-3.2.2-bin.zip
- Linux OS: apache-maven-3.2.2-bin.tar.gz
- Mac OS: apache-maven-3.2.2-bin.tar.gz
Note: This OBE shows you how to install and create a Java SE application using Maven in a Windows operating system.
Click Start, right-click Computer, and select Properties.

On the Control Panel home page, click Advanced system settings.
In the System Properties dialog box, click the Advanced tab, and then click Environment Variables.

The Environment Variables dialog box is displayed.
Click New, add M2, M2_HOME, and MAVEN_OPTS to the environment variables, and click OK.
Under System variables, click New, enter the following values in the Edit System variable dialog box, and click OK:
- Variable name: Path
- Variable value: %M2% (Enter the value after bin in the system path)
Verify the Maven installation:
mvn -version

The output displays the installed Maven version, the Java version, the Java home, the Default locale, and the OS name.

Creating a Java SE Project from a Maven Template

Open the command prompt, navigate to the directory where you installed Maven, and create Maven_app, a Maven-based Java application folder:

mvn archetype:generate
                                -DgroupId=com.example.bank

                                   -DartifactId=OracleBanking

                                  
                                -DarchetypeArtifactId=maven-archetype-quickstart
                                

                                   -DinteractiveMode=false

An archetype is an original pattern/model for creating similar projects. In Maven, an archetype is a template of a project that is combined with user input to produce a working Maven project. The following table describes what the template does:

Archetype ArtifactIds	Description
`mvn archetype:generate`	Creates a project
`-DgroupId=com.example.bank`	Creates the `com.example.bank` dependency package structure
`maven-archetype-quickstart`	Creates a Java project
`-DinteractiveMode=false`	Sets interactive mode to `false`

The Java project named OracleBanking is created. The following table presents the project details:

Project Structure	Description
`OracleBanking`	Contains `src` folder and `pom.xml`
`src/main/java`	Contains Java code files under the package structure (`com.example/bank`)
`src/test`	Contains test code files under the package structure (`com.example/bank`)
`pom.xml`	Contains information about the project and details of various configurations used by Maven to build the project

Open the OracleBanking project and verify the Java source file:

App.java

Verify Java test file:
AppTest.java

By default, Maven adds the App.java source file and the AppTest.java test file to the default directory structure.

Open the pom.xml file and review the code.

Each project has a single pom.xml file, and each pom.xml file has a project element and three mandatory fields: groupId, artifactId, and version. Notice that Maven has already added JUnit as the test framework. The following table describes what each node does:

Node	Description
`project`	Top-level element in all Maven `pom.xml` files
`modelVersion`	Object model version that this POM is using
`groupId`	Project groupId (for example, `com.example.bank`)
`artifactId`	Project ID (for example, `OracleBanking`)
`packaging`	Project files converted into a JAR file
`version`	Project version used in the artifact's repository to separate each version (for example, `1.0-SNAPSHOT`)
`name`	Project display name
`url`	Location of the project site

Creating and Modifying Java Source Files

In this section, you calculate simple interest by creating the SimpleInterest.java source file and modifying the App.java source file.

Navigate to the directory where you created your Maven project, and then open the specified location:

\**\Maven_app\OracleBanking\src\main\java\com\example\bank
Create a Java source file named SimpleInterest.java.

Edit the SimpleInterest.java file with the following code:

package com.example.bank;                                                                                                   public class SimpleInterest{                                                                                                     public static double calculateSimpleInterest(double amount,
	         double years,
	         double rate_of_interest) {
	double simple_interest;
	simple_interest = amount * years * rate_of_interest;
	return simple_interest;
     }                                                                                                                       }

The calculateSimpleInterest method calculates the interest rate on the loan amount, the tenure of the loan, and the rate of interest per annum.

Press Ctrl+S and close the file.

Modify App.java with the following code:

double result = SimpleInterest.calculateSimpleInterest(10000, 5, 7);
System.out.println("The simple interest is:" + result);                                                                                                                                                                                                 public static double calculateSimpleInterest(double amount,
	    double years,
	    double rate_of_interest) {
	double simple_interest;
	simple_interest = amount * years * rate_of_interest;
	return simple_interest;
}

Review the code. It should look like the following:
Press Ctrl+S and close the file.

Creating a Manifest with Maven

In this section, you learn how to use maven-jar-plugin to create a manifest file and package it by adding it to the JAR file.

The manifest file performs the following tasks:

Defines the entry point of the project and creates an executable JAR file.
Adds the class path of the project dependencies.

Edit the pom.xml file:

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>2.4</version>
                <configuration>
                    <archive>
                        <manifest>
                            <mainClass>com.example.bank.App</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>
        </plugins>
    </build>

You defined maven-jar-plugin in pom.xml, and configured it within the configuration tag.

Review the code. It should look like the following:

In the Maven project, you specify the main class details by updating the pom.xml file. The com.example.bank.App class in the project is the main class that will be executed when you execute the JAR file.
Press Ctrl+S and close the file.

You successfully updated your pom.xml file.

Testing, Building, and Running the Application Using Maven

Testing the Application

In this section, you learn how to test your application with AppTest.java using the Maven command-line interface (CLI).

Import the package into AppTest.java:

import junit.framework.Assert;

Edit the AppTest method:

 double result=App.calculateSimpleInterest(10000,5,7);
 Assert.assertEquals("Test failed. ",35000.0,result);

Review the code. It should look like the following:

You modified the simple interest value, and then verified the value by using assert statements in the JUnit test case.
Press Ctrl+S and then run the test cases in AppTest.java inside the OracleBanking project.
mvn test
Review the output.

The test case failed and the assert failed message is displayed.
Modify AppTest.java:
```
 Assert.assertEquals("Test failed. ", 350000.0, result);  
```
You modified the simple interest value, and then verified the value by using assert statements in the JUnit test case.
Press Ctrl+S and then run the test cases in AppTest.java:
mvn test

The test case executed successfully, and a build success message is displayed.

Building the Application

In this section, you learn how to clean and build your application using the Maven CLI.

Clean and build your Maven project, and review the output:
mvn clean package

You successfully built the OracleBanking Java SE application using Maven.
Navigate to the directory where you created OracleBanking and notice that a target folder was created.

Open the target folder, and review the folder structure.

Folder name	Description
`classes`	Contains `.class` files of Java source files
`test-classes`	Contains `.class` files of Java test files
`maven-archiver`	Contains the `pom.properties` file
`surefire-reports`	Contains the report of the application when `mvn` command is executed.
`java`	Empty Java file
`OracleBanking-1.0-SNAPSHOT.jar`	Contains all the project related details in a single zip file. This is the executable JAR file used to run the application

Packaging and Running the Application

In this section, you learn how to package and run the Java SE project using the Maven CLI.

Navigate to the directory where you installed Maven, and open the settings.xml file.

The <localRepository> tag specifies the local repository location on your machine. By default, the local repository is created in the %USER_HOME% directory. You can specify another location by updating it in the settings.xml file. If you need to set proxy details for the application, then update it in the settings.xml file.
Clean and package the files, plug-ins, and libraries before running the application:
mvn clean package
Use the Maven Local repository to run your Java SE Maven application:
mvn exec:java -Dexec.mainClass="com.example.bank.App" -s "*****location of settings.xml file.********"
Review the output.

You successfully executed the Java SE application named OracleBanking using Maven. The simple interest is calculated and displayed in the Maven CLI.
Execute the JAR file with following commands:
cd target
java -jar OracleBanking-1.0-SNAPSHOT.jar
Review the output.

You successfully executed the OracleBanking Java SE application by using Maven. The simple interest is calculated and displayed in the Maven CLI.

Want to Learn More?

Maven Quick Guide
Maven Getting Started Guide
Installing and Configuring Maven for Build Automation and Dependency Management in Oracle Fusion Middleware Developing Applications Using Continuous Integration

Credits

Curriculum Developer: Shilpa Chetan


                        
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Building and Running a Java SE Application by Using Maven

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