scalamolecule / molecule   0.18.0

Molecule is a Scala 3 library to query SQL and NoSQL databases with the words of your domain.

Compose an immutable "molecule" data structure:

Person.name.age.Address.street

instead of building queries

SELECT
  Person.name,
  Person.age,
  Address.street
FROM Person
  INNER JOIN Address 
    ON Person.address = Address.id;

[:find ?name ?age ?street
 :where [?a :Person/name ?name]
        [?a :Person/age ?age]
        [?a :Ns/address ?b]
        [?b :Address/street ?street]]

and get typed data matching the molecule from the database:

val persons: List[(String, Int, String)] =
  Person.name.age.Address.street.query.get

Data can also be fetched asynchronously in a Future, cats IO or ZIO.

• Support for PostgreSQL, SQlite, MySQL, MariaDB, H2 and Datomic databases. More can easily be added
• Molecules for any database behave identically. Each db pass the same SPI compliance test suite (+1700 tests).
• Targets Scala >=3.3.5 on JVM and JS platforms
• Synchronous, Asynchronous (Future), ZIO and cats.effect.IO APIs
• All Scala primitive types and collection types available as molecule attributes (!)
• Typed methods to compose even complex molecules:
  • Filter/aggregation functions
  • Validation
  • Nested and optional relationships
  • Sorting
  • Pagination (offset/cursor)
  • Subscriptions
• Molecules on ScalaJS side transparently operates server database with no JSON marshalling/wiring setup
• Fast transparent binary serialization between Client and Server with Boopickle (no manual setup)
• No macros
• No complex type class implicits
• Maximum type inference in IDE to easily choose available attributes/expressions/relationships

1. Define the entity names and attributes of your domain structure with Molecule's meta DSL

object MyDomain extends DomainStructure(5) { 

  trait Person {
    val name     = oneString
    val age      = oneInt
    val birthday = oneLocalDate 
    val address  = one[Address]
  }

  trait Address {
    val street = oneString
    val zip    = oneString
    val city   = oneString
  }
}

2. Run sbt compile -Dmolecule=true once to generate molecule-enabling boilerplate code and db schemas.
3. Compose fluent molecules with your domain terms to save and read data from your database.

Molecules using any Database/API combination return the same data, just in different wrappings:

Synchronous API, Datomic

import molecule.datalog.datomic.sync._

val persons: List[(String, Int, String)] =
  Person.name.age.Address.street.query.get

Synchronous API, PostgreSQL

import molecule.sql.postgres.sync._

val persons: List[(String, Int, String)] =
  Person.name.age.Address.street.query.get

Asynchronous API

import molecule.sql.postgres.async._

val persons: Future[List[(String, Int, String)]] =
  Person.name.age.Address.street.query.get

ZIO API

import molecule.sql.postgres.Zio._

val persons: ZIO[Conn, MoleculeError, List[(String, Int, String)]] =
  Person.name.age.Address.street.query.get

IO API

import molecule.sql.postgres.io._

val persons: cats.effect.IO[List[(String, Int, String)]] =
  Person.name.age.Address.street.query.get

Save one entity

Person
  .name("Bob")
  .age(42)
  .Address
  .street("Baker st")
  .save.transact

Insert multiple entities

Person.name.age.Address.street.insert(
  ("Bob", 42, "Baker st"),
  ("Liz", 38, "Bond road")
).transact

Update

Person(bobId).age(43).update.transact

Delete

Person(bobId).delete.transact

Clone molecule-samples and use one of the template projects to get started.

git clone https://github.com/scalamolecule/molecule-samples.git

Add the following to your build files:

project/build.properties:

sbt.version = 1.10.11

project/plugins.sbt:

addSbtPlugin("org.scalamolecule" % "sbt-molecule" % "1.13.0")

build.sbt:

lazy val yourProject = project.in(file("app"))
  .enablePlugins(MoleculePlugin)
  .settings(
    libraryDependencies ++= Seq(
      // One or more of:
      "org.scalamolecule" %%% "molecule-sql-postgres" % "0.18.0",
      "org.scalamolecule" %%% "molecule-sql-sqlite" % "0.18.0",
      "org.scalamolecule" %%% "molecule-sql-mysql" % "0.18.0",
      "org.scalamolecule" %%% "molecule-sql-mariadb" % "0.18.0",
      "org.scalamolecule" %%% "molecule-sql-h2" % "0.18.0",
      "org.scalamolecule" %%% "molecule-datalog-datomic" % "0.18.0",
    ),
    
    // Paths to directories with your domain structure definition files
    moleculeDomainPaths := Seq("app") 
  )

The coreTests module in this repo has several domain structure definitions and +1700 tests that show all details of how molecule can be used. This forms the Service Provider Interface (SPI) that each database implementation needs to comply with in order to offer all functionality of Molecule and be a valid implementation.

First, clone the molecule project to your computer (or git pull to get the latest changes):

git clone https://github.com/scalamolecule/molecule.git
cd molecule

Then run some tests on either ScalaJVM or ScalaJS:

Make sure Docker is running to run tests for Postgres, SQlite, Mysql and MariaDB. Datomic and H2 can be run in memory for tests. On a mac you can for instance start Docker Desktop.

Run the coreTests on the jvm with a databases of your choice:

sbt sqlPostgresJVM/test
sbt sqlSQliteJVM/test
sbt sqlMysqlJVM/test
sbt sqlMariadbJVM/test
sbt sqlH2JVM/test
sbt datalogDatomicJVM/test

To test using molecules from ScalaJS, you need to have a ScalaJVM backend server running in a separate process that can receive the queries and send data back to ScalaJS.

In the server module you can see 7 different minimal Tapir backend setups that you can start out from and successively add your own api endpoints to. In one process you can start up one of those backends where you will be asked which backend you want to use:

sbt server/run

Multiple main classes detected. Select one to run:
 [1] molecule.server.Armeria
 [2] molecule.server.Http4s
 [3] molecule.server.Netty
 [4] molecule.server.Pekko
 [5] molecule.server.Play
 [6] molecule.server.VertX
 [7] molecule.server.ZioHttp

Enter number: 

Let's enter 3 to use the Netty server:

Enter number: 3
[info] running molecule.server.Netty 
Press ENTER to stop the server.
✅ Netty server running on http://localhost:8080

Now we have a backend running on ScalaJVM ready to take care of your molecule queries from ScalaJS!

In another process you can then run one of the following commands to run the coreTests on ScalaJS with the database of your choice:

sbt datalogDatomicJS/test
sbt sqlH2JS/test
sbt sqlMariaDBJS/test
sbt sqlMySQLJS/test
sbt sqlPostgreSQLJS/test
sbt sqlSQliteJS/test

The tests are then automatically fetching data from the running backend - Molecule takes care of it transparently!

Marc Grue

Molecule is licensed under the Apache License 2.0