There are several ways to create project. It can be done by IDE default wizard or generate via spring initializer. Even these are convenient to us to setup project, but for organization it might has some custom libraries and organization-specific settings (e.g. private repositories, etc)

In this article, we will show how to create a project to support both Maven and Gradle.

This demo will use folder named java-project-template as example.

Prerequisites

Python and cookiecutter should be installed properly.

// Install Python
sudo apt install -y python

// Install CookieCutter
pip install cookiecutter

Steps

Create CookieCutter project structure.
In command prompt, execute command below:
```
mkdir {{cookiecutter.__projectFolder}}
mkdir hooks
```

Create cookiecutter.json
In the same folder, create file named cookiecutter.json and input content as below:

{
  "javaVersion": ["17", "19", "11", "1.8"],
  "projectType": ["gradle", "maven"],
  "group": "io.github",
  "artifact": "demo-library",
  "version": "1.0.0-SNAPSHOT",
  "__projectName": "{{cookiecutter.group}}.{{cookiecutter.artifact}}",
  "__projectFolder" : "{{cookiecutter.artifact}}",
  "__projectPackageRoot" : "{{cookiecutter.group.lower()}}.{{cookiecutter.artifact.lower().replace('-','.') }}",
}

Remind that property __projectFolder should be same as the folder name in step 1, otherwise it cannot be render.

Create project template structure.
In command prompt, execute command below:

cd {{cookiecutter.__projectFolder}}
mkdir gradle
mkdir src/main
mkdir src/test

Create maven related file.
In folder {{cookiecutter.__projectFolder}} , create file named pom.xml and input content below:

<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>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>{{cookiecutter.group}}</groupId>
    <artifactId>{{cookiecutter.artifact}}</artifactId>
    <version>{{cookiecutter.version}}</version>
    <name>{{cookiecutter.__projectName}}</name>

    <properties>
        <maven.compiler.source>{{cookiecutter.javaVersion}}</maven.compiler.source>
        <maven.compiler.target>{{cookiecutter.javaVersion}}</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <junit-version>latest</junit-version>
        <mockito.version>latest</mockito.version>
    </properties>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.junit/junit-bom -->
        <dependency>
            <groupId>org.junit</groupId>
            <artifactId>junit-bom</artifactId>
            <version>${junit-version}</version>
            <type>pom</type>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-junit-jupiter</artifactId>
            <version>${mockito.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-inline</artifactId>
            <version>${mockito.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.1</version>
                </plugin>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-javadoc-plugin</artifactId>
                    <version>3.5.0</version>
                    <configuration>
                        <reportOutputDirectory>docs</reportOutputDirectory>
                        <destDir>docs</destDir>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.jacoco</groupId>
                    <artifactId>jacoco-maven-plugin</artifactId>
                    <version>0.8.9</version>
                    <configuration>
                        <excludes>
                            <exclude>docs/**</exclude>
                        </excludes>
                    </configuration>
                <executions>
                    <execution>
                        <id>prepare-agent</id>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>report</id>
                        <phase>test</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                    <groupId>org.owasp</groupId>
                    <artifactId>dependency-check-maven</artifactId>
                    <version>8.2.1</version>
                    <executions>
                        <execution>
                            <goals>
                                <goal>check</goal>
                            </goals>
                        </execution>
                    </executions>
                    <configuration>
                        <name>Dependency Check Report</name>
                        <formats>
                            <format>HTML</format>
                            <format>JSON</format>
                        </formats>
                    </configuration>
                </plugin>
            <plugin>
                <groupId>org.sonarsource.scanner.maven</groupId>
                <artifactId>sonar-maven-plugin</artifactId>
                <version>3.9.1.2184</version>
            </plugin>

            </plugins>
        </pluginManagement>
    </build>
</project>

Create Gradle related file.
In folder {{cookiecutter.__projectFolder}} , create file named pom.xml and input content below:

plugins {
    id("java")
    id("org.owasp.dependencycheck") version "8.2.1"
}

group = "{{cookiecutter.group}}.{{cookiecutter.artifact}}"
version = "{{cookiecutter.version}}"

repositories {
    mavenCentral()
}

dependencies {
    testImplementation(platform("org.junit:junit-bom:5.1.0"))
    testImplementation("org.junit.jupiter:junit-jupiter")
}

tasks.test {
    useJUnitPlatform()
}

tasks.withType<Javadoc> {
    val javaSrcDir = project.file("src/main/java")
    source = project.files(javaSrcDir).asFileTree
    classpath += project.files(sourceSets["main"].output)
    destinationDir = project.file("docs/javadoc")
}

Create post render script.
In folder hook, create file named post_gen_project.py and input as below:

import os;

def init_directories():
    print("Initialize main program.")
    mainRootDirectory = "src/main/java/"+"{{cookiecutter.__projectPackageRoot}}".lower().replace(".", "/")
    os.makedirs(mainRootDirectory)
    os.rename("src/main/package-info.java", mainRootDirectory+"/package-info.java")
    os.rename("src/main/Main.java", mainRootDirectory+"/Main.java")

    print("Initialize test program.")
    testRootDirectory = "src/test/java/"+"{{cookiecutter.__projectPackageRoot}}".lower().replace(".", "/")
    os.makedirs(testRootDirectory)
    os.rename("src/test/package-info.java", testRootDirectory+"/package-info.java")
    os.rename("src/test/MainTest.java", testRootDirectory+"/MainTest.java")

    print("Clean up project.")
    match "{{cookiecutter.projectType}}":
        case "gradle":
            cleanup_maven()
        case "maven":
            cleanup_gradle()
        
def cleanup_maven():
    os.remove("pom.xml")
    os.remove(".github/workflows/CI-Maven.yaml")

def cleanup_gradle():
    os.rmdir("gradle")
    os.remove("build.gradle.kts")
    os.remove("gradlew")  
    os.remove("gradlew.bat")  
    os.remove("settings.gradle.kts")
    os.remove(".github/workflows/CI-Gradle.yaml")

def main():
    init_directories()

if __name__ == "__main__":
    main()

Method init_directories() is used to create package structure with package name provided; And it will clean up unused files.