https://github.com/nryanov/neo4s

neo4s - scala wrapper for neo4j
https://github.com/nryanov/neo4s

cats cats-effect neo4j scala

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neo4s - scala wrapper for neo4j

• Host: GitHub
• URL: https://github.com/nryanov/neo4s
• Owner: nryanov
• License: apache-2.0
• Created: 2020-04-29T21:44:59.000Z (over 4 years ago)
• Default Branch: master
• Last Pushed: 2022-05-12T20:24:14.000Z (over 2 years ago)
• Last Synced: 2024-10-27T21:41:49.317Z (about 2 months ago)
• Topics: cats, cats-effect, neo4j, scala
• Language: Scala
• Homepage:
• Size: 102 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 8
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# neo4s

Neo4s - scala wrapper for [Neo4j](https://github.com/neo4j/neo4j).

The core ideas were taken from [doobie](https://github.com/tpolecat/doobie). 

## Install

```sbt

libraryDependencies ++= Seq(

  "com.nryanov.neo4s" %% "neo4s-core" % "[version]"

)

```

## Usage example

```scala

import neo4s._

import neo4s.implicits._

import cats.effect.{ExitCode, IO, IOApp}

import cats.syntax.flatMap._

object BasicSample extends IOApp {

  private val NEO4J_URI = "bolt://localhost:7687/db/neo4j"

  case class Address(street: String)

  case class Person(name: String, age: Int, address: Address)

  override def run(args: List[String]): IO[ExitCode] = Neo4jTransactor.create[IO](NEO4J_URI).use { transactor =>

    val name = "Sherlock Holmes"

    val age = 60

    val street = "221B Baker Street"

    val query = for {

      _ <- cypher"create (n:Person {name: $name, age: $age, address: $street})".update.run

      person <- cypher"match (n:Person {name: $name}) return n.name, n.age, n.address".query[Person].unique

    } yield person

    query

      .transact(transactor)

      .flatTap(returnedName => IO.delay(println(s"Returned person: $returnedName")))

      // Returned person: Person(Sherlock Holmes,60,Address(221B Baker Street))

      .map(_ => ExitCode.Success)

      .handleErrorWith(error => IO.delay(println(s"Error: ${error.getLocalizedMessage}")).map(_ => ExitCode.Error))

  }

}

```

## Notes

As this library is just a wrapper for java driver, all threading management is done by underlying driver.

## Custom mappings

By default, `neo4s` provides `Get[A]` and `Put[A]` (`Meta[A]`) for:

- JVM numeric types Byte, Short, Int, Long, Float, and Double;

- BigDecimal and BigInteger;

- Boolean, Char, String, and Array[Byte];

- Date, Time, and Timestamp from the java.sql package;

- LocalDate, LocalTime, LocalDateTime, OffsetTime, OffsetDateTime and ZonedDateTime from the java.time package; and

- List[A], Array[A], Map[String, A]

- single-element case classes wrapping one of the above types.

### Deriving Get and Put for custom type

To derive Get and Put instances for custom type you can use existing Meta[_]:

```scala

sealed abstract class Digit(val value: Int)

case object One extends Digit(1)

case object Two extends Digit(2)

case class Another(value: Int) extends Digit(value)

implicit val digitMeta: Meta[Digit] = Meta[Int].imap {

  case 1 => One

  case 2 => Two

  case x => Another(x)

} {

  digit => digit.value

}

```

Also, you can do the same but using existing Put/Get:

```scala

implicit val digitGet: Get[Digit] = Get[Int].map {

  case 1 => One

  case 2 => Two

  case x => Another(x)

}

implicit val digitPut: Put[Digit] = Put[Int].contramap(digit => digit.value)

```