为什么astyanax(java)不能识别scala case类参数列表中的@id注释值？

Question

场景1--Case类

Astyanax无法在val上获取注释@id

@Entity
case class Organization(@Id @Column(name = "id") override val id: Option[UUID] = None,
                        @Column(name = "created_on") override val createdOn: Option[Date] = None,
                        @Column(name = "modified_on") override val modifiedOn: Option[Date] = None,
                        @Column(name = "name") name: Option[String] = None,
                        @Column(name = "is_paid_account") isPaidAccount: Boolean = false) extends IdBaseEntity[UUID](id, createdOn, modifiedOn)

场景2-有伴生对象的类或无伴生对象的类

@Entity
class Organization(@Id @Column(name = "id") override val id: Option[UUID] = None,
                       @Column(name = "created_on") override val createdOn: Option[Date] = None,
                       @Column(name = "modified_on") override val modifiedOn: Option[Date] = None,
                       @Column(name = "name") name: Option[String] = None,
                       @Column(name = "is_paid_account") isPaidAccount: Boolean = false) extends IdBaseEntity[UUID](id, createdOn, modifiedOn)

object Organization {
  def apply(id: Option[UUID] = None,
            createdOn: Option[Date] = None,
            modifiedOn: Option[Date] = None,
            name: Option[String] = None,
            isPaidAccount: Boolean = false) = new Organization(id, createdOn, modifiedOn, name, isPaidAccount)
}

@Entity
case class Organization(@Id @Column(name = "id") override val id: Option[UUID] = None,
                        @Column(name = "created_on") override val createdOn: Option[Date] = None,
                        @Column(name = "modified_on") override val modifiedOn: Option[Date] = None,
                        @Column(name = "name") name: Option[String] = None,
                        @Column(name = "is_paid_account") isPaidAccount: Boolean = false) extends IdBaseEntity[UUID](id, createdOn, modifiedOn) {
  @Id @Column(name = "id") val theId: Option[UUID] = id
}

除了#3，我在类块中声明了一个val，而不是case类或常规类/常规类的参数列表，我的每个场景都失败了。Astyanax说，该类中有一个know成员用@id注释，所以它会抛出异常。在我进一步挖掘之前，我想我应该询问社区关于注释scala类和将其发送到执行反射的java库之间的细微差别。来源没有什么特别的。事实上，以下是失败的相关行:https://github.com/netflix/astyanax/blob/master/astyanax-entity-mapper/src/main/java/com/netflix/astyanax/entitystore/entitymapper.java#l89-120

class CassandraOrganizationDAO extends BaseCassandraDAO[Organization, UUID](Astyanax.context) with OrganizationDAO {
  val ColumnFamilyOrganizations: ColumnFamily[UUID, String] = new ColumnFamily[UUID, String](
    "organizations",
    TimeUUIDSerializer.get(),
    StringSerializer.get(),
    ByteBufferSerializer.get())

  val ColumnFamilyOrganizationMembers: ColumnFamily[UUID, UUID] = new ColumnFamily[UUID, UUID](
    "organization_members",
    TimeUUIDSerializer.get(),
    TimeUUIDSerializer.get(),
    DateSerializer.get())

  val manager: EntityManager[Organization, UUID] = new DefaultEntityManager.Builder[Organization, UUID]()
    .withEntityType(classOf[Organization])
    .withKeyspace(getKeyspace())
    .withColumnFamily(ColumnFamilyOrganizations)
    .build()

 // the rest of the class is omitted 
}

Answer 1

我遇到了一个类似的问题，在构造函数的字段中从来没有考虑到我的注释。实际上，我使用了SpringData，不可能直接将注释（如@indexed)映射到字段上。

要在case类的构造函数中启用批注，首先应该创建这样的类：

object FixedScalaAnnotations {
  type Id = com.packagecontainingid.Id @field //replace by the right package
  type Column = com.packagecontainingcolumn.Column @field
}

然后在case类中导入它，并使用它来代替原始的：

import FixedScalaAnnotations._

@Entity
case class Organization(@Id @Column(name = "id") override val id: Option[UUID] = None,
                        @Column(name = "created_on") override val createdOn: Option[Date] = None,
                        @Column(name = "modified_on") override val modifiedOn: Option[Date] = None,
                        @Column(name = "name") name: Option[String] = None,
                        @Column(name = "is_paid_account") isPaidAccount: Boolean = false) extends IdBaseEntity[UUID](id, createdOn, modifiedOn)

确保没有使用原始软件包。

这里有一篇关于JPA的相关文章:http://blog.fakod.eu/2010/07/14/constructor-arguments-with-jpa-annotations/