belongsTo relationship obligatory
I don't want to define typeWine as an optional value, but if i don't put it, I have to declare typeWine in the extract method and I don't know how to do that.
In the documentacion of Skinny ORM, it doesn't describe how to do this, and I'm getting stuck.
package app.models.wine
import scalikejdbc._
import skinny.orm.SkinnyCRUDMapper
case class Wine (id: Option[Long], typeWine: Option[Type] = None, name: String)
object Wine extends SkinnyCRUDMapper[Wine] {
override def defaultAlias = createAlias("w")
override def extract (rs: WrappedResultSet, n: ResultName[Wine]): Wine = new Wine(
id = rs.get(n.id),
name = rs.get(n.name)
)
belongsTo[Type](Type, (w, t) => w.copy(typeWine = t)).byDefault
}
package app.models.wine
import scalikejdbc._
import skinny.orm.SkinnyCRUDMapper
case class Type (id: Option[Long], typeName: String)
object Type extends SkinnyCRUDMapper[Type] {
override def defaultAlias = createAlias("t")
override def columnNames = Seq("id", "type_name")
override def extract (rs: WrappedResultSet, n: ResultName[Type]): Type = new Type(
id = rs.get(n.id),
typeName = rs.get(n.typeName)
)
}
Defining belongsTo/byDefault relationship to typeWine and extracting typeWine value with its resultName should work for you.
Related
My use case has case classes something like
case class Address(name:String,pincode:String){
override def toString =name +"=" +pincode
}
case class Department(name:String){
override def toString =name
}
case class emp(address:Address,department:Department)
I want to create a DSL like below.Can anyone share the links about how to create a DSL and any suggestions to achieve the below.
emp.withAddress("abc","12222").withDepartment("HR")
Update:
Actual use case class may have more fields close to 20. I want to avoid redudancy of code
I created a DSL using reflection so that we don't need to add every field to it.
Disclamer: This DSL is extremely weakly typed and I did it just for fun. I don't really think this is a good approach in Scala.
scala> create an Employee where "homeAddress" is Address("a", "b") and "department" is Department("c") and that_s it
res0: Employee = Employee(a=b,null,c)
scala> create an Employee where "workAddress" is Address("w", "x") and "homeAddress" is Address("y", "z") and that_s it
res1: Employee = Employee(y=z,w=x,null)
scala> create a Customer where "address" is Address("a", "b") and "age" is 900 and that_s it
res0: Customer = Customer(a=b,900)
The last example is the equivalent of writing:
create.a(Customer).where("address").is(Address("a", "b")).and("age").is(900).and(that_s).it
A way of writing DSLs in Scala and avoid parentheses and the dot is by following this pattern:
object.method(parameter).method(parameter)...
Here is the source:
// DSL
object create {
def an(t: Employee.type) = new ModelDSL(Employee(null, null, null))
def a(t: Customer.type) = new ModelDSL(Customer(null, 0))
}
object that_s
class ModelDSL[T](model: T) {
def where(field: String): ValueDSL[ModelDSL2[T], Any] = new ValueDSL(value => {
val f = model.getClass.getDeclaredField(field)
f.setAccessible(true)
f.set(model, value)
new ModelDSL2[T](model)
})
def and(t: that_s.type) = new { def it = model }
}
class ModelDSL2[T](model: T) {
def and(field: String) = new ModelDSL(model).where(field)
def and(t: that_s.type) = new { def it = model }
}
class ValueDSL[T, V](callback: V => T) {
def is(value: V): T = callback(value)
}
// Models
case class Employee(homeAddress: Address, workAddress: Address, department: Department)
case class Customer(address: Address, age: Int)
case class Address(name: String, pincode: String) {
override def toString = name + "=" + pincode
}
case class Department(name: String) {
override def toString = name
}
I really don't think you need the builder pattern in Scala. Just give your case class reasonable defaults and use the copy method.
i.e.:
employee.copy(address = Address("abc","12222"),
department = Department("HR"))
You could also use an immutable builder:
case class EmployeeBuilder(address:Address = Address("", ""),department:Department = Department("")) {
def build = emp(address, department)
def withAddress(address: Address) = copy(address = address)
def withDepartment(department: Department) = copy(department = department)
}
object EmployeeBuilder {
def withAddress(address: Address) = EmployeeBuilder().copy(address = address)
def withDepartment(department: Department) = EmployeeBuilder().copy(department = department)
}
You could do
object emp {
def builder = new Builder(None, None)
case class Builder(address: Option[Address], department: Option[Department]) {
def withDepartment(name:String) = {
val dept = Department(name)
this.copy(department = Some(dept))
}
def withAddress(name:String, pincode:String) = {
val addr = Address(name, pincode)
this.copy(address = Some(addr))
}
def build = (address, department) match {
case (Some(a), Some(d)) => new emp(a, d)
case (None, _) => throw new IllegalStateException("Address not provided")
case _ => throw new IllegalStateException("Department not provided")
}
}
}
and use it as emp.builder.withAddress("abc","12222").withDepartment("HR").build().
You don't need optional fields, copy, or the builder pattern (exactly), if you are willing to have the build always take the arguments in a particular order:
case class emp(address:Address,department:Department, id: Long)
object emp {
def withAddress(name: String, pincode: String): WithDepartment =
new WithDepartment(Address(name, pincode))
final class WithDepartment(private val address: Address)
extends AnyVal {
def withDepartment(name: String): WithId =
new WithId(address, Department(name))
}
final class WithId(address: Address, department: Department) {
def withId(id: Long): emp = emp(address, department, id)
}
}
emp.withAddress("abc","12222").withDepartment("HR").withId(1)
The idea here is that each emp parameter gets its own class which provides a method to get you to the next class, until the final one gives you an emp object. It's like currying but at the type level. As you can see I've added an extra parameter just as an example of how to extend the pattern past the first two parameters.
The nice thing about this approach is that, even if you're part-way through the build, the type you have so far will guide you to the next step. So if you have a WithDepartment so far, you know that the next argument you need to supply is a department name.
If you want to avoid modifying the origin classes you can use implicit class, e.g.
implicit class EmpExtensions(emp: emp) {
def withAddress(name: String, pincode: String) {
//code omitted
}
// code omitted
}
then import EmpExtensions wherever you need these methods
I still get the same error, I have defined the marshaller (and imported it); it appears that the case class entry is not in context when the function is polymorphic. and this throws a Cannot find JsonWriter or JsonFormat type class for Case Class. Is there a reason why spray-json can not find the implicit marshaller for the case class, (even when defined) is this case class in context? Link to marshaller
import spray.json._
import queue.MedusaJsonProtocol._
object MysqlDb {
...
}
case class UserDbEntry(
id: Int,
username: String,
countryId: Int,
created: LocalDateTime
)
trait MysqlDb {
implicit lazy val pool = MysqlDb.pool
}
trait HydraMapperT extends MysqlDb {
val FetchAllSql: String
def fetchAll(currentDate: String): Future[List[HydraDbRow]]
def getJson[T](row: T): String
}
object UserHydraDbMapper extends HydraMapperT {
override val FetchAllSql = "SELECT * FROM user WHERE created >= ?"
override def fetchAll(currentDate: String): Future[List[UserDbEntry]] = {
pool.sendPreparedStatement(FetchAllSql, Array(currentDate)).map { queryResult =>
queryResult.rows match {
case Some(rows) =>
rows.toList map (x => rowToModel(x))
case None => List()
}
}
}
override def getJson[UserDbEntry](row: UserDbEntry): String = {
HydraQueueMessage(
tableType = HydraTableName.UserTable,
payload = row.toJson.toString()
).toJson.toString()
}
private def rowToModel(row: RowData): UserDbEntry = {
UserDbEntry (
id = row("id").asInstanceOf[Int],
username = row("username").asInstanceOf[String],
countryId = row("country_id").asInstanceOf[Int],
created = row("created").asInstanceOf[LocalDateTime]
)
}
}
payload = row.toJson.toString() Can't find marshaller for UserDbEntry
You have defined UserDbEntry locally and there is no JSON marshaller for that type. Add the following:
implicit val userDbEntryFormat = Json.format[UserDbEntry]
I'm not sure how you can call row.toJson given UserDbEntry is a local case class. There must be a macro in there somewhere, but it's fairly clear that it's not in scope for the local UserDbEntry.
Edit
Now that I see your Gist, it looks like you have a package dependency problem. As designed, it'll be circular. You have defined the JSON marshaller in package com.at.medusa.core.queue, which imports UserDbEntry, which depends on package com.at.medusa.core.queue for marshalling.
I'm new to Slick thus I'm not sure whether the problem caused by incorrect usage of implicits or Slick doesn't allow doing what I'm trying to do.
In short I use Slick-pg extension for JSONB support in Postgres. I also use spray-json to deserialize JSONB fields into case classes.
In order to automagically convert columns into objects I wrote generic implicit JsonColumnType that you can see below. It allows me to have any case class for which I defined json formatter to be converted to jsonb field.
On the other hand I want to have alias of JsValue type for the same column so that I can use JSONB-operators.
import com.github.tminglei.slickpg._
import com.github.tminglei.slickpg.json.PgJsonExtensions
import org.bson.types.ObjectId
import slick.ast.BaseTypedType
import slick.jdbc.JdbcType
import spray.json.{JsValue, RootJsonWriter, RootJsonReader}
import scala.reflect.ClassTag
trait MyPostgresDriver extends ExPostgresDriver with PgArraySupport with PgDate2Support with PgRangeSupport with PgHStoreSupport with PgSprayJsonSupport with PgJsonExtensions with PgSearchSupport with PgNetSupport with PgLTreeSupport {
override def pgjson = "jsonb" // jsonb support is in postgres 9.4.0 onward; for 9.3.x use "json"
override val api = MyAPI
private val plainAPI = new API with SprayJsonPlainImplicits
object MyAPI extends API with DateTimeImplicits with JsonImplicits with NetImplicits with LTreeImplicits with RangeImplicits with HStoreImplicits with SearchImplicits with SearchAssistants { //with ArrayImplicits
implicit val ObjectIdColumnType = MappedColumnType.base[ObjectId, Array[Byte]](
{ obj => obj.toByteArray }, { arr => new ObjectId(arr) }
)
implicit def JsonColumnType[T: ClassTag](implicit reader: RootJsonReader[T], writer: RootJsonWriter[T]) = {
val columnType: JdbcType[T] with BaseTypedType[T] = MappedColumnType.base[T, JsValue]({ obj => writer.write(obj) }, { json => reader.read(json) })
columnType
}
}
}
object MyPostgresDriver extends MyPostgresDriver
Here is how my table is defined (minimized version)
case class Article(id : ObjectId, ids : Ids)
case class Ids(doi: Option[String], pmid: Option[Long])
class ArticleRow(tag: Tag) extends Table[Article](tag, "articles") {
def id = column[ObjectId]("id", O.PrimaryKey)
def idsJson = column[JsValue]("ext_ids")
def ids = column[Ids]("ext_ids")
private val fromTuple: ((ObjectId, Ids)) => Article = {
case (id, ids) => Article(id, ids)
}
private val toTuple = (v: Article) => Option((v.id, v.ids))
def * = ProvenShape.proveShapeOf((id, ids) <> (fromTuple, toTuple))(MappedProjection.mappedProjectionShape)
}
private val articles = TableQuery[ArticleRow]
Finally I have function that looks up articles by value of json field
def getArticleByDoi(doi : String): Future[Article] = {
val query = (for (a <- articles if (a.idsJson +>> "doi").asColumnOf[String] === doi) yield a).take(1).result
slickDb.run(query).map { items =>
items.headOption.getOrElse(throw new RuntimeException(s"Article with doi $doi is not found"))
}
}
Sadly I get following exception in runtime
java.lang.ClassCastException: spray.json.JsObject cannot be cast to server.models.db.Ids
The problem is in SpecializedJdbcResultConverter.base where ti.getValue is being called with wrong ti. It should be slick.driver.JdbcTypesComponent$MappedJdbcType but instead it's com.github.tminglei.slickpg.utils.PgCommonJdbcTypes$GenericJdbcType. As result wrong type is passed into my tuple converter.
What makes Slick choose different type for column even though there is explicit definition of projection in table row class ?
Sample project that demonstrates the issue is here.
I'm using scala and slick here, and I have a baserepository which is responsible for doing the basic crud of my classes.
For a design decision, we do have updatedTime and createdTime columns all handled by the application, and not by triggers in database. Both of this fields are joda DataTime instances.
Those fields are defined in two traits called HasUpdatedAt, and HasCreatedAt, for the tables
trait HasCreatedAt {
val createdAt: Option[DateTime]
}
case class User(name:String,createdAt:Option[DateTime] = None) extends HasCreatedAt
I would like to know how can I use reflection to call the user copy method, to update the createdAt value during the database insertion method.
Edit after #vptron and #kevin-wright comments
I have a repo like this
trait BaseRepo[ID, R] {
def insert(r: R)(implicit session: Session): ID
}
I want to implement the insert just once, and there I want to createdAt to be updated, that's why I'm not using the copy method, otherwise I need to implement it everywhere I use the createdAt column.
This question was answered here to help other with this kind of problem.
I end up using this code to execute the copy method of my case classes using scala reflection.
import reflect._
import scala.reflect.runtime.universe._
import scala.reflect.runtime._
class Empty
val mirror = universe.runtimeMirror(getClass.getClassLoader)
// paramName is the parameter that I want to replacte the value
// paramValue is the new parameter value
def updateParam[R : ClassTag](r: R, paramName: String, paramValue: Any): R = {
val instanceMirror = mirror.reflect(r)
val decl = instanceMirror.symbol.asType.toType
val members = decl.members.map(method => transformMethod(method, paramName, paramValue, instanceMirror)).filter {
case _: Empty => false
case _ => true
}.toArray.reverse
val copyMethod = decl.declaration(newTermName("copy")).asMethod
val copyMethodInstance = instanceMirror.reflectMethod(copyMethod)
copyMethodInstance(members: _*).asInstanceOf[R]
}
def transformMethod(method: Symbol, paramName: String, paramValue: Any, instanceMirror: InstanceMirror) = {
val term = method.asTerm
if (term.isAccessor) {
if (term.name.toString == paramName) {
paramValue
} else instanceMirror.reflectField(term).get
} else new Empty
}
With this I can execute the copy method of my case classes, replacing a determined field value.
As comments have said, don't change a val using reflection. Would you that with a java final variable? It makes your code do really unexpected things. If you need to change the value of a val, don't use a val, use a var.
trait HasCreatedAt {
var createdAt: Option[DateTime] = None
}
case class User(name:String) extends HasCreatedAt
Although having a var in a case class may bring some unexpected behavior e.g. copy would not work as expected. This may lead to preferring not using a case class for this.
Another approach would be to make the insert method return an updated copy of the case class, e.g.:
trait HasCreatedAt {
val createdAt: Option[DateTime]
def withCreatedAt(dt:DateTime):this.type
}
case class User(name:String,createdAt:Option[DateTime] = None) extends HasCreatedAt {
def withCreatedAt(dt:DateTime) = this.copy(createdAt = Some(dt))
}
trait BaseRepo[ID, R <: HasCreatedAt] {
def insert(r: R)(implicit session: Session): (ID, R) = {
val id = ???//insert into db
(id, r.withCreatedAt(??? /*now*/))
}
}
EDIT:
Since I didn't answer your original question and you may know what you are doing I am adding a way to do this.
import scala.reflect.runtime.universe._
val user = User("aaa", None)
val m = runtimeMirror(getClass.getClassLoader)
val im = m.reflect(user)
val decl = im.symbol.asType.toType.declaration("createdAt":TermName).asTerm
val fm = im.reflectField(decl)
fm.set(??? /*now*/)
But again, please don't do this. Read this stackoveflow answer to get some insight into what it can cause (vals map to final fields).
in order to implement a ReSTfull APIs stack, I need to convert data extracted from a DB to JSON format. I think that the best way is to extract data from the DB and then convert the row set to JSON using Json.toJson() passing as argument a case class after having defined a implicit serializer (writes).
Here's my case class and companion object:
package deals.db.interf.slick2
import scala.slick.driver.MySQLDriver.simple._
import play.api.libs.json.Json
case class PartnerInfo(
id: Int,
name: String,
site: String,
largeLogo: String,
smallLogo: String,
publicationSite: String
)
object PartnerInfo {
def toCaseClass( ?? ) = { // what type are the arguments to be passed?
PartnerInfo( fx(??) ) // how to transform the input types (slick) to Scala types?
}
// Notice I'm using slick 2.0.0 RC1
class PartnerInfoTable(tag: Tag) extends Table[(Int, String, String, String, String, String)](tag, "PARTNER"){
def id = column[Int]("id")
def name = column[String]("name")
def site = column[String]("site")
def largeLogo = column[String]("large_logo")
def smallLogo = column[String]("small_logo")
def publicationSite = column[String]("publication_site")
def * = (id, name, site, largeLogo, smallLogo, publicationSite)
}
val partnerInfos = TableQuery[PartnerInfoTable]
def qPartnerInfosForPuglisher(publicationSite: String) = {
for (
pi <- partnerInfos if ( pi.publicationSite == publicationSite )
) yield toCaseClass( _ ) // Pass all the table columns to toCaseClass()
}
implicit val partnerInfoWrites = Json.writes[PartnerInfo]
}
What I cannot get is how to implement the toCaseClass() method in order to transform the column types from Slick 2 to Scala types - notice the function fx() in the body of toCaseClass() is only meant to give emphasis to that.
I'm wondering if is it possible to get the Scala type from Slick column type because it is clearly passed in the table definition, but I cannot find how to get it.
Any idea?
I believe the simplest method here would be to map PartnerInfo in the table schema:
class PartnerInfoTable(tag: Tag) extends Table[PartnerInfo](tag, "PARTNER"){
def id = column[Int]("id")
def name = column[String]("name")
def site = column[String]("site")
def largeLogo = column[String]("large_logo")
def smallLogo = column[String]("small_logo")
def publicationSite = column[String]("publication_site")
def * = (id, name, site, largeLogo, smallLogo, publicationSite) <> (PartnerInfo.tupled, PartnerInfo.unapply)
}
val partnerInfos = TableQuery[PartnerInfoTable]
def qPartnerInfosForPuglisher(publicationSite: String) = {
for (
pi <- partnerInfos if ( pi.publicationSite == publicationSite )
) yield pi
}
Otherwise PartnerInfo.tupled should do the trick:
def toCaseClass(pi:(Int, String, String, String, String, String)) = PartnerInfo.tupled(pi)