Add support for custom maven repositories with credentials

[tgeens]

In our custom instance we would like to add a maven repository which requires credentials.

For maven projects, this works because the user can define the credentials in ~/.m2/settings.xml while referencing the maven repository-id.

For gradle projects this doesn't work. The gradle-way to accomplish this, looks like this:

maven {
       url 'https://artifacts.mycompany.com/snapshots'
       credentials {
                username property("com.mycompany.artifacts.username")
                password property("com.mycompany.artifacts.password")
        }
}

This is currently not supported by Initializr.

[tgeens]

My proposal:

1. Add a credentials field to the MavenRepository model. The type would be a MavenRepositoryCredentials object with username & password fields. (Or a key-value map-like object, which would facilitate extending this to non-basic-auth later on.)

2a. The maven-build-writer can ignore the credentials field - just like the gradle-build-writer is ignoring the name and snapshotsEnabled fields from MavenRepository

2b. The gradle-build-writer can check if there are (non-default) credentials provided and write those to the build.gradle if necessary. Currently the gradle-build-writer can only write repositories on a single line (like maven { url 'https://repo.spring.io/snapshot' }).

To support a representation which includes credentials info, the implementation of GradleBuildWriter#writeRepositories should be updated and the method signature

protected abstract String repositoryAsString(MavenRepository repository)

should change into something that can (optionally) write multi-line repository information, like

protected void writeRepository(IndentingWriter writer, MavenRepository repository)

[otheriault]

Since it it not mentioned explicitly in this issue, I think it would be equally valid to support maven repository credentials in the settings.gradle#pluginManagement like this:

pluginManagement {
    repositories{
        maven {
            url 'https://artifacts.mycompany.com/snapshots'
               credentials {
                  username property("com.mycompany.artifacts.username")
                  password property("com.mycompany.artifacts.password")
              }
        }
        gradlePluginPortal()
    }
}

There is also limited extensibility here since the GradleSettingsWriter#repositoryAsString is private as well as most of the writeX methods.

[wilkinsona]

For Gradle 6.6 and later, we can use their new credential handling support. For earlier versions of Gradle we can mimic that support by writing out property lookups with the property names derived from the repository's name. This will allow common configuration to be written out in different ways by version-specific writers.

[srinivasvsk]

will this be addressed at some point?

[wilkinsona]

We hope to address it at some point, that's why the issue has not be closed. We don't have any firm plans or a date in mind at the moment, however.