Java Project Structure

Overview

This is a short lesson to help learners understand the basic of java project structure. It will help to pace learners towards lesson 3.10 on spring maven.

Coverage

1. Generate java project with maven
2. Understanding java project structure
   • src folder
   • target folder
3. Understanding package keyword
4. Proper way to run java project

Pre-requisites: - Java (you should have already installed) - Maven

Run sdk install maven before going through the steps.

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1. Generate Java Project with Maven

Command to generate java project:

mvn archetype:generate -DgroupId=com.edisonzsq.javaproject -DartifactId=javaproject -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

Terminology	Meaning
archetype	default project template provided by maven
artifact	the output of a project compilation such as .class or .jar file. Or even image for container hosting.
groupId	the package path

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2. Understanding Project Structure

The immediate file(s) and folders from the project root directory are:

Summary Table:

Folder	Purpose
src	Where your source code lives
target	Where your compiled lives
src/main	Where your application code lives
src/test	Where your test code lives
target/classes	Where your compiled application code lives
target/test-lasses	Where your compiled test code lives
pom.xml	Stores project metadata and dependency information

Test codes are written to ensure the software behaves according to expectations

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3. Understanding package

The What and Why

The package is a reserved keyword in java and it can be applied once in every java class. We use it to categorize our code.

The How

Example of package names:

Package	Purpose
com.edisonzsq.javaproject.controllers	Receive API Calls
com.edisonzsq.javaproject.services	Business Logics
com.edisonzsq.javaproject.dataaccess	Database Layer
com.edisonzsq.javaproject.utils	Utility classes such as thousand separator formatting for currency value

You would realize how these package path matches the project folder structure within src/main/java.

For now we have to rely on your imagination. This project is just a brief. There is not controllers, services, dataaccess, or utils folder. We will see more of that in the spring boot project.

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4. Running Java Project

Step 1: Running mvn package would compile the project (produce an artifact). Or, mvn clean package to remove previous artifact and compile again.

Step 2: Add manifest to pom.xml

Add the following to pom.xml within the <project> tag, same level as <dependencies>.

  <build>
    <finalName>App</finalName>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.1.2</version>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass>com.edisonzsq.javaproject.App</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
  </build>

Please adjust the value for <finalName> and <mainClass> according to your project.

Step 3: Execute the .jar file.

java -jar ./target/App.jar

End