Question

我使用Quill库编写了这个简单的应用程序来查询Cassandra

QuillSample.scala

import java.util.UUID
import io.getquill._
import scala.concurrent.ExecutionContext.Implicits.global
object QuillSample extends App {
   lazy val ctx = new CassandraSyncContext[SnakeCase]("ctx")
   import ctx._
   val getAllRows = quote {
      query[Movies]
   }
   val result = ctx.run(getAllRows)
   println(result)
}
case class Movies(uUID: UUID,
                  avgRating: Float,
                  genres: Set[String],
                  name: String,
                  releaseDate: java.util.Date,
                  videoReleaseDate: java.util.Date)

build.sbt

name := "QuillSample"
version := "1.0"
scalaVersion := "2.12.0"
libraryDependencies ++= Seq(
   "io.getquill" % "quill-cassandra_2.11" % "1.0.0"
)

application.properties

ctx.keyspace=movielens_small
ctx.preparedStatementCacheSize=1000
ctx.session.contactPoint=192.168.1.169
ctx.session.withPort=9042
ctx.session.queryOptions.consistencyLevel=LOCAL_QUORUM
ctx.session.withoutMetrics=true
ctx.session.withoutJMXReporting=false
ctx.session.maxSchemaAgreementWaitSeconds=1
ctx.session.addressTranslater=com.datastax.driver.core.policies.IdentityTranslator

这将返回编译时错误

Error:(14, 12) Can't find an implicit `SchemaMeta` for type `com.abhi.Movies`
      query[Movies]

基于此处提供的文件

https://github.com/getquill/quill/blob/master/CASSANDRA.md

我不确定需要哪些其他代码来满足缺少的隐式。

Answer 1

Quill尚不支持Scala 2.12。跟踪this PR进度。

更改scalaVersion：

scalaVersion := "2.11.8"

此外，由于在1.0.0版本之后生成的this fix，您必须使用快照依赖性：

resolvers ++= Seq(
  Resolver.sonatypeRepo("snapshots")
)

libraryDependencies ++= Seq(
  "io.getquill" %% "quill-cassandra" % "1.0.2-SNAPSHOT"
)

接下来，您必须为scala.collection.Set[T]实现自定义编码器和解码器：

trait Encoders {
  this: CassandraSessionContext[_] =>

  implicit def setEncoder[T](implicit t: ClassTag[T]): Encoder[Set[T]] =
    encoder((index, value, row) => row.setSet(index, value.asJava, t.runtimeClass.asInstanceOf[Class[T]]))
}

trait Decoders {
  this: CassandraSessionContext[_] =>

  implicit def setDecoder[T](implicit t: ClassTag[T]): Decoder[Set[T]] =
    decoder((index, row) => row.getSet(index, t.runtimeClass.asInstanceOf[Class[T]]).asScala.toSet)
}

并在你的背景下混合：

lazy val ctx = new CassandraSyncContext[SnakeCase]("ctx") with Encoders with Decoders

可能会收到警告：

找不到类javax.annotation.Nullable - 继续存根。

要修复它，请添加以下依赖项：

libraryDependencies ++= Seq(
  "com.google.code.findbugs" % "jsr305" % "3.0.1"
)

Answer 2

所以看起来你没有能够构建com.abhi.Movies的SchemaMeta所以你需要明确指定一个

implicit val movieSchemaMeta = schemaMeta[com.abhi.Movies](....)

无法找到类型的隐式`SchemaMeta`

2 个答案: