title: TypeConverters cannot figure out how to save this field into database
body: <p>I got an error when implementing the type converter of Room.</p>
  
  <blockquote>
    <p>error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
        <code>private java.util.List&lt;? extends java.util.Map&lt;java.lang.String, mypage.profile.entity.OtherServiceEntity&gt;&gt; otherServices;</code></p>
  </blockquote>
  
  <p>This is my implementation, 
  Firstly config the entity like below, because the POJO contain List of Map I implemented the Room's TypeConverter like this</p>
  
  <pre><code>object OtherServicesTypeConverter {
      private val gson = Gson()
      @TypeConverter
      @JvmStatic
      fun stringToList(data: String?): List&lt;Map&lt;String, OtherServiceEntity&gt;&gt; {
          if (data == null) {
              return Collections.emptyList()
          }
  
          val listType = object : TypeToken&lt;List&lt;Map&lt;String, OtherServiceEntity&gt;&gt;&gt;() {
  
          }.type
  
          return gson.fromJson&lt;List&lt;Map&lt;String, OtherServiceEntity&gt;&gt;&gt;(data, listType)
      }
  
      @TypeConverter
      @JvmStatic
      fun listToString(objects: List&lt;Map&lt;String, OtherService&gt;&gt;): String {
          return gson.toJson(objects)
      }
  }
  </code></pre>
  
  <p>Then using annotation inside the entity, and database as below</p>
  
  <pre><code>@Entity(tableName = "ProfileEntities")
      data class ProfileEntity(
              @PrimaryKey
              @SerializedName("masterId") var masterId: Long = 0,
              @SerializedName("nickname") var nickname: String = "",
              @TypeConverters(OtherServicesTypeConverter::class)
              @SerializedName("otherServices") var otherServices: List&lt;Map&lt;String, OtherServiceEntity&gt;&gt;,
              @Embedded
              @SerializedName("images") var images: ProfileImagesEntity = ProfileImagesEntity(),
              @SerializedName("updatedAt") var updatedAt: String = ""
      )
  
  
   @Database(entities = [ArticleFeatureEntity::class, ProfileEntity::class], version = 3)
      @TypeConverters(DataTypeConverter::class, ProfileTypeConverter::class, OtherServicesTypeConverter::class)
      abstract class AppDatabase : RoomDatabase() {
          abstract fun profileDao(): ProfileDao
          // Code here
  
  
      }
  </code></pre>
  
  <p>Please help to support me, thank you!</p>