[英]how to generate a java array from a scala case class
I'm writing a small data access library to help me use Cassandra prepared statements in a Scala program (its not open source but maybe one day). 我正在编写一个小型数据访问库,以帮助我在Scala程序中使用Cassandra准备的语句(它不是开源的,但可能有一天)。 What I'd like to do is automatically generate a Java Array for the bind statement from the case class 我想做的是为case类的bind语句自动生成一个Java Array。
com.datastax.driver.core
PreparedStatement...
public BoundStatement bind(Object... values);
So currently I have 所以目前我有
case class Entity(foo:String, optionalBar:Option[String])
object Entity {
def toJArray(e:Entity) = { Array(e.foo, e.optionalBar.getOrElse(null)) }
}
val e1 = Entity("fred", Option("bill"))
val e2 = Entity("fred", None)
Entity.toJArray(e1)
res5: Array[String] = Array(fred, bill)
Entity.toJArray(e2)
res6: Array[String] = Array(fred, null)
The toJArray returns an Array I can use in the bind statement. toJArray返回一个我可以在bind语句中使用的Array。 The boiler plate code gets worse if there is a date or double or a java enum 如果有日期,双精度数或Java枚举,则样板代码会变得更糟
new java.util.Date(createdOn)
scala.Double.box(price)
priceType.name
Is there a way of automatically generating the Array in Scala assuming the bind parameters have the same order as the case class fields? 假设绑定参数与case类字段具有相同的顺序,是否可以在Scala中自动生成Array?
EDIT Thanks to @srgfed01 Here's what I came up with (not complete) but allows me to do something like 编辑感谢@ srgfed01这是我想出的(不完整),但允许我做类似的事情
val customer1 = Customer( "email", "name", None, Option(new Date), OrdStatus.New)
session.execute(populate(customer1, insert))
val customer2 = Customer( "email2", "name2", Option(22), Option(new Date), OrdStatus.Rejected)
session.execute(populate(customer2, insert))
using this function 使用此功能
def populate(state:Product, statement:PreparedStatement): BoundStatement = {
def set(bnd:BoundStatement, i:Int, aval:Any): Unit = {
aval match {
case v:Date => bnd.setDate(i, v)
case v:Int => bnd.setInt(i, v)
case v:Long => bnd.setLong(i, v)
case v:Double => bnd.setDouble(i, v)
case v:String => bnd.setString(i, v)
case null => bnd.setToNull(i)
case _ => bnd.setString(i, aval.toString)
}
}
val bnd = statement.bind
for(i <- 0 until state.productArity) {
state.productElement(i) match {
case op: Option[_] => set(bnd, i, op.getOrElse(null))
case v => set(bnd, i, v)
}
}
bnd
}
You can use productIterator
call for your case
class object: 您可以将productIterator
调用用于您的case
类对象:
case class Entity(foo: String, optionalBar: Option[String])
val e1 = Entity("fred", Option("bill"))
val e2 = Entity("fred", None)
def run(e: Entity): Array[Any] = e.productIterator
.map {
case op: Option[_] => op.getOrElse(null)
case v => v
}
.toArray
println(run(e1).mkString(" ")) // fred bill
println(run(e2).mkString(" ")) // fred null
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.