[JAVA] Build a Maven repository on AWS S3

If you need a Maven repository

There are many cases where you want to manage Java libraries in a private environment such as in-house. At a certain scale, we will introduce Nexus, but there are times when we want to make it a little easier. This entry is a way to build a Maven repository using AWS S3.

procedure

Create and use Maven repository in the following order.

1. Create a bucket for Maven repository on S3
2. Create a user to access the S3 Maven repository
3. Library registration settings with Gradle plugin
4. Client settings for using the library

1. Create a bucket for the Maven repository

There is nothing special to mention, and as usual, create a bucket for S3. Let's say you created a bucket called my-maven.

2. Create a user to access the Maven repository

Although not required, create a user for the Maven repository and add S3 permissions for proper access control. Also, at this timing, you will get the AWS ʻAccess key ID and Secret access key`.

Access policy

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:ListAllMyBuckets"
            ],
            "Resource": "arn:aws:s3:::*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "s3:*"
            ],
            "Resource": [
                "arn:aws:s3:::my-maven",
                "arn:aws:s3:::my-maven/*"
            ]
        }
    ]
}

3. Library registration settings with Gradle plugin

Apply the maven-publish plugin and configure the settings for registering the library.

build.gradle

apply plugin: 'maven-publish'

def tag = System.getenv('CIRCLE_TAG') //Detects git tag push(Example for CircleCI)
def buildVersion = "1.0.0"
group = 'com.example'
version = tag ? "${tag}-RELEASE" : "${buildVersion}-SNAPSHOT" //RELEASE for tag push, SNAPSHOT otherwise(This area is specified according to the actual operation)

//To include the source in the library registered in the repository
task sourceJar(type: Jar) {
    from sourceSets.main.allJava
}

publishing {
    repositories {
        maven {
            url "s3://my-maven"
            credentials(AwsCredentials) {
                accessKey System.getenv('AWS_ACCESS_KEY_ID')
                secretKey System.getenv('AWS_SECRET_ACCESS_KEY')
            }
        }
    }
    publications {
        mavenJava(MavenPublication) {
            from components.java
            artifact sourceJar {
                classifier "sources"
            }
        }
    }
}

Build the source and register the repository with the following commands. Normally, you will use it via CI etc.

$ gradle publish

4. Client settings for using the library

If you add the created Maven repository on the client side, you can use it like any other repository.

build.gradle

repositories {
	mavenCentral()
	//Add the following
	maven {
		url "s3://my-maven"
		credentials(AwsCredentials) {
			accessKey System.getenv('AWS_ACCESS_KEY_ID')
			secretKey System.getenv('AWS_SECRET_ACCESS_KEY')
		}
	}
}

Summary

It's easy to build, so it's a great way to manage your library when you need it. Also, this example was Gradle, but you can do the same with Maven.