scala 讀取配置到案例類地圖的地圖

Question

我需要從一個配置文件中讀取並將配置映射到一個案例類。如果我有一個如下表，它工作正常

配置

mapping {
   target {
     oracle  = {
         type = "oracle"
         schema    = "orcl"
         tableName = "my_table"
         query = "select key from my_table where dob='2020-01-01'
     }
}

SCALA 代碼片段

 val targetConfig:Map[String,QueryEngine] = config.getObject("mapping.target")
    .entrySet()
    .asScala
    .foldLeft(Map.empty[String , QueryEngine]) { case ( acc , entry ) =>
      val target = entry.getKey
      val targetConfig = entry.getValue match {
        case validElement if validElement.valueType() == ConfigValueType.OBJECT  => validElement.asInstanceOf[ConfigObject].toConfig
        case invalidElement => sys.error("illegal syntax at $invalidElement")
      }

      targetConfig.getString("type")    match {

        case "oracle" => acc + (target ->  new OracleQueryEngine(vars,target,targetConfig.getString("schema"),targetConfig.getString("tableName"),targetConfig.getString("query"),targetConfig.getString("param")))

        case  x   => sys.error(s"unknow target not defined $targetConfig with $targetConfig")
      }
    }

現在我用目標映射中的 MULTIPLE 表更新了 CONFIG。

mapping {
   target {
     oracle  =   
        emp = {
         type = "oracle"
         schema    = "orcl"
         tableName = "emp"
         query = "select key from emp where dob='2020-01-01'
        }
        dept = {
         type = "oracle"
         schema    = "orcl"
         tableName = "dept"
         query = "select key from dept where dob='2020-01-01'
        }
    }
}

多表場景的代碼片段這給出了 mutable.Set[Map[String,QueryEngine]] 的錯誤表達式不確認 Map[Query,String]

 val targetConfig:Map[String,QueryEngine] = config.getObject("mapping.target")
    .entrySet()
    .asScala
    .foldLeft(Map.empty[String , QueryEngine]) { case ( acc , entry ) =>
      val target = entry.getKey
      val targetConfig = entry.getValue match {
        case validElement if validElement.valueType() == ConfigValueType.OBJECT  => validElement.asInstanceOf[ConfigObject].toConfig
        case invalidElement => sys.error("illegal syntax at $invalidElement")
      }
      targetConfig.getObject(s"mapping.target.$target").keySet().asScala.map { key =>
        target  match {
          case "oracle" => acc + (target ->  new OracleQueryEngine(vars,target,targetConfig.getString("schema"),targetConfig.getString("tableName"),targetConfig.getString("query"),targetConfig.getString("param")))

          case  x   => sys.error(s"unknow target not defined $targetConfig with $targetConfig")
        }
      }

  }

純配置代碼

import pureconfig._
import pureconfig.generic.ProductHint
import pureconfig.generic.auto._
import com.typesafe.config.ConfigFactory
import pureconfig._
import pureconfig.generic.auto._

object PureconfigExample {

  case class QueryEngine(`type`: String, schema: String, tableName: String, query: String)
  type  DatabaseConfig = Map[String, Map[String, QueryEngine]]
  case class TargetConfig(target: DatabaseConfig)
  case class ApplicationConfig(mapping: TargetConfig)

  def main(args: Array[String]): Unit = {
    val configString =
      """
        |mapping {
        |   target {
        |     oracle {
        |        emp {
        |         type = "oracle"
        |         schema    = "orcl"
        |         tableName = "emp"
        |         query = "select key from emp where dob='2020-01-01'"
        |        }
        |        dept  {
        |         type = "oracle"
        |         schema    = "orcl"
        |         tableName = "dept"
        |         query = "select key from dept where dob='2020-01-01'"
        |        }
        |      }
        |    }
        |}
        |""".stripMargin

    import pureconfig.generic.auto._

    // See for more details - https://pureconfig.github.io/docs/overriding-behavior-for-case-classes.html
    implicit def hint[T]: ProductHint[T] = ProductHint[T](ConfigFieldMapping(CamelCase, CamelCase))

    val config = ConfigSource.string(configString).load[ApplicationConfig]
    println(config)
  }
}

POM文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>test2</groupId>
    <artifactId>test2</artifactId>
    <version>1.0-SNAPSHOT</version>


<dependencies>
    <dependency>
        <groupId>com.github.pureconfig</groupId>
        <artifactId>pureconfig-generic-base_2.12</artifactId>
        <version>0.12.2</version>
    </dependency>
    <dependency>
        <groupId>com.github.pureconfig</groupId>
        <artifactId>pureconfig-generic_2.12</artifactId>
        <version>0.12.0</version>
    </dependency>
</dependencies>

</project>

編譯器錯誤

PureConfigExample.scala
Error:(43, 56) Cannot find an implicit instance of pureconfig.ConfigReader[PureconfigExample.ApplicationConfig].
If you are trying to read or write a case class or sealed trait consider using PureConfig's auto derivation by adding `import pureconfig.generic.auto._`
    val config = ConfigSource.string(configString).load[ApplicationConfig]
Error:(43, 56) not enough arguments for method load: (implicit reader: pureconfig.Derivation[pureconfig.ConfigReader[PureconfigExample.ApplicationConfig]])pureconfig.ConfigReader.Result[PureconfigExample.ApplicationConfig].
Unspecified value parameter reader.
    val config = ConfigSource.string(configString).load[ApplicationConfig]

Answer 1

對不起，可能不是您可能期望的答案，但我強烈建議您避免手動配置解析，因為有一些工具可以自動為您執行此操作，同時無需樣板代碼和類型安全。 Scala 生態系統中最受歡迎且可能是最好的庫是PureConfig 。 所以在你的情況下，解決方案看起來像這樣：

import pureconfig._
import pureconfig.generic.ProductHint
import pureconfig.generic.auto._

object PureconfigExample {

  case class QueryEngine(`type`: String, schema: String, tableName: String, query: String)
  type  DatabaseConfig = Map[String, Map[String, QueryEngine]]
  case class TargetConfig(target: DatabaseConfig)
  case class ApplicationConfig(mapping: TargetConfig)

  def main(args: Array[String]): Unit = {
    val configString =
      """
        |mapping {
        |   target {
        |     oracle {
        |        emp {
        |         type = "oracle"
        |         schema    = "orcl"
        |         tableName = "emp"
        |         query = "select key from emp where dob='2020-01-01'"
        |        }
        |        dept  {
        |         type = "oracle"
        |         schema    = "orcl"
        |         tableName = "dept"
        |         query = "select key from dept where dob='2020-01-01'"
        |        }
        |      }
        |    }
        |}
        |""".stripMargin

    // See for more details - https://pureconfig.github.io/docs/overriding-behavior-for-case-classes.html
    implicit def hint[T]: ProductHint[T] = ProductHint[T](ConfigFieldMapping(CamelCase, CamelCase))

    val config = ConfigSource.string(configString).load[ApplicationConfig]
    println(config)
  }
}

在我的情況下產生下一個結果：

Right(ApplicationConfig(TargetConfig(Map(oracle -> Map(emp -> QueryEngine(oracle,orcl,emp,select key from emp where dob='2020-01-01'), dept -> QueryEngine(oracle,orcl,dept,select key from dept where dob='2020-01-01'))))))

希望這有幫助！