How Easy is It to migrate Dependencies of pom.xml to build.gradle

In Part 1 The Age Of Gradle, we go throw about Ant, Maven and Gradle.

I mentioned that we can use the combination of Maven and Gradle so I will share you how to do it.

The combination will be complex and depend on various use cases so I cannot cover all in one post. In this post, I just share Gradle script to import Maven dependencies from pom.xml file to gradle.build without any modification in pom.xml file.

GitHub Repository

This is my origin pom file.

Pom.xml

<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>

    <name>Ogirin Maven Project</name>
    <groupId>jp.btuan.express</groupId>
    <artifactId>sample</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>

    <properties>
        <version.jackson>2.8.8</version.jackson>
        <version.guava>23.0</version.guava>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>${version.jackson}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.8.8</version>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>${version.guava}</version>
        </dependency>
    </dependencies>
</project>

And this is customized build.gradle file. You can see under dependencies block, I implemented script to read pom.xml file, get dependencies and version. Then load into gradle project.

Build.gradle

group 'jp.btuan.express'
version '1.0'

apply plugin: 'java'

sourceCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {

    // Load dependencies from old pom.xml file
    def pomXml = new XmlSlurper().parse('pom.xml')
    def pomDependencies = pomXml.dependencies.dependency
    pomDependencies.each { dependency ->
        // Get Dependency version
        def dependencyVersion = "${dependency.version}"
        if (dependencyVersion.matches("^\$\{\S*\}$")){
            dependencyVersion = dependencyVersion.replaceAll("[\$\{\}]", "");
            dependencyVersion = pomXml.properties."${dependencyVersion}"
        }else{
            dependencyVersion = "${dependency.version}"
        }
        def dependencySpec = "${dependency.groupId}:${dependency.artifactId}:${dependencyVersion}"
        println dependencySpec
        switch (dependency.scope){
            case 'test':
                dependencies.add 'testCompile', dependencySpec
                break;
            case 'runtime':
                dependencies.add 'runtime', dependencySpec
                break;
            default:
                dependencies.add 'compile', dependencySpec
                break;
        }
    }

    // Define dependencies with Gradle syntax
    compile group: 'com.google.code.gson', name: 'gson', version: '2.8.2'
}

Is it easy? Give me feedback if there are any to help it better.

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