OrientDB Manual 1.7.8

Scala API

OrientDB is a NoSQL database writen in Java, we can use it in scala easily. Look also at Scala utilities and tests project for Scala high level classes built on top of OrientDB.

Java method invocation problems

Usually the main problems are related to calling conventions between Scala and Java.

Parameters

Be careful to pass parameters to methods with varargs like db.query(...). You need to convert it to java's repeated args correctly.

Look at these links: http://stackoverflow.com/questions/3022865/calling-java-vararg-method-from-scala-with-primitives http://stackoverflow.com/questions/1008783/using-varargs-from-scala http://stackoverflow.com/questions/3856536/how-to-pass-a-string-scala-vararg-to-a-java-method-using-scala-2-8

Collections

You can only use java collections when define pojos. If you use scala collections, they can be persisted, but can't be queried.

This's not a problem, if you imported:

import scala.collection.JavaConverters._
import scala.collection.JavaConversions._

You don't need to convert Java and Scala collections manually (even don't need to invoke .asJava or .asScala) You can treat these java collections as scala's.

models.scala

package models

import javax.persistence.{Version, Id}

class User {
    @Id var id: String = _
    var name: String = _
    var addresses: java.util.List[Address] = new java.util.ArrayList()
    @Version var version: String = _

    override def toString = "User: " + this.id + ", name: " + this.name + ", addresses: " + this.addresses
}

class Address {
    var city: String = _
    var street: String = _

    override def toString = "Address: " + this.city + ", " + this.street
}

class Question {
    @Id var id: String = _
    var title: String = _
    var user: User = _
    @Version var version: String = _

    override def toString = "Question: " + this.id + ", title: " + this.title + ", belongs: " + user.name
}

test.scala

package models

import com.orientechnologies.orient.core.id.ORecordId
import com.orientechnologies.orient.core.sql.query.OSQLSynchQuery
import scala.collection.JavaConverters._
import scala.collection.JavaConversions._
import com.orientechnologies.orient.core.db.`object`.{ODatabaseObject, ODatabaseObjectPool, OObjectDatabaseTx}

object Test {
    implicit def dbWrapper(db: OObjectDatabaseTx) = new {
        def queryBySql[T](sql:-String,-params:-AnyRef*.md): List[T] = {
            val params4java = params.toArray
            val results: java.util.List[T] = db.query(new OSQLSynchQuery[T](sql.md), params4java: _*)
            results.asScala.toList
        }
    }

    def main(args: Array[String]) = {
        // ~~~~~~~~~~~~~ create db ~~~~~~~~~~~~~~~~~~~
        var uri: String = "local:test/orientdb"
        var db: OObjectDatabaseTx = new OObjectDatabaseTx(uri)
        if (!db.exists) {
            db.create()
        } else {
            db.open("admin", "admin")
        }

        // ~~~~~~~~~~~~ register models ~~~~~~~~~~~~~~~~
        db.getEntityManager.registerEntityClasses("models")

        // ~~~~~~~~~~~~~ create some data ~~~~~~~~~~~~~~~~
        var user: User = new User
        user.name = "aaa"
        db.save(user)

        var address1 = new Address
        address1.city = "NY"
        address1.street = "road1"
        var address2 = new Address
        address2.city = "ST"
        address2.street = "road2"

        user.addresses += address1
        user.addresses += address2
        db.save(user)

        var q1 = new Question
        q1.title = "How to use orientdb in scala?"
        q1.user = user
        db.save(q1)

        var q2 = new Question
        q2.title = "Show me a demo"
        q2.user = user
        db.save(q2)

        // ~~~~~~~~~~~~~~~~ count them ~~~~~~~~~~~~~~~~
        val userCount = db.countClass(classOf[User])
        println("User count: " + userCount)

        val questionCount = db.countClass(classOf[Question])
        println("Question count: " + questionCount)

        // ~~~~~~~~~~~~~~~~~ get all users ~~~~~~~~~~~~
        val users = db.queryBySql[User]("select-from-User".md)
        for (user <- users) {
            println(" - user: " + user)
        }

        // ~~~~~~~~~~~~~~~~~~ get the first user ~~~~~~~~
        val firstUser = db.queryBySql[User]("select-from-User-limit-1".md).head
        println("First user: " + firstUser)

        // query by id
        val userById = db.queryBySql[User]("[email protected]=-?",-new-ORecordId(user.id))
        println("User by id: " + userById)

        // query by field
        val userByField = db.queryBySql[User]("select-from-User-where-name-=-?",-user.name)
        println("User by field: " + userByField)

        // query by city
        val userByCity = db.queryBySql[User]("select-from-User-where-addresses-contains-(-city-=-?-.md)", "NY")
        println("User by city: " + userByCity)

        // query questions of the user
        val questions = db.queryBySql[Question]("select-from-Question-where-user-=-?",-user.md)
        for (q <- questions) {
            println(" - question: " + q)
        }

        db.drop()
        db.close()
    }
}