ROOM constructors failed to match on build

Question

When building my app, I am getting an error with two entity classes. It's basically saying it cannot find the setter for the constructors I am giving. Originally I had vals, I converted these to vars and that seems to fix the issue.

But I don't like this fix... The documentation uses vals in their examples of how to build entities. So why does it not work for certain entities I define? I feel like the coding I'm doing is going to be prone to some sort of error because I am only bandaging the problem rather than actually fixing it.

https://developer.android.com/training/data-storage/room/defining-data

data class DirectMessage(
    @PrimaryKey
    @ColumnInfo(name = "dm_id")  override val objectId: String,

    //Author of message
    @Ignore override val author: User,

    //Recipient of message, usually user of the app
    @Ignore override val recipient: User,

    //Content of message
    override val content: String,
    //Date of creation
    override val timestamp: Long

) : DirectMessage {

    //Place identifier into database instead of Entity
    @ColumnInfo(name = "author") val _author : String = author.uid
    @ColumnInfo(name = "recipient") val _recipient : String = recipient.uid

    /**
     * Get author's user thumbnail
     */
    override fun getThumbnail() {
        TODO("Not yet implemented")
    }

}

@Entity
data class Comment (

    @PrimaryKey
    @ColumnInfo(name = "cid") override val objectId: String,

    //Author of the comment
    @Ignore override val author: User,

    //Moment ID this comment is attached to
    override var momentId: String,

    //Time comment was created
    override val timestamp: Long,

    //Content of the comment
    override var content: String

    ) : Comment {

    //Place identifier into database instead of User entity
    @ColumnInfo(name = "author") val _author = author.uid

    /**
     * Get thumbnail of User object
     */
    override fun getThumbnail() {
        TODO("Not yet implemented")
    }

}

interface Comment : Message {

    val momentId : String
}

public final class Comment implements com.example.barrechat192.data.entities.Comment {
             ^
  Tried the following constructors but they failed to match:
  Comment(java.lang.String,com.example.barrechat192.data.entities.User,java.lang.String,long,java.lang.String) -> [param:objectId -> matched field:objectId, param:author -> matched field:unmatched, param:momentId -> matched field:momentId, param:timestamp -> matched field:timestamp, param:content -> matched field:content]C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\Comment.java:13: error: Cannot find setter for field.
    private final java.lang.String _author = null;
                                   ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\Comment.java:17: error: Cannot find setter for field.
    private final java.lang.String objectId = null;
                                   ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\Comment.java:23: error: Cannot find setter for field.
    private final long timestamp = 0L;
                       ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\DirectMessage.java:7: error: Entities and POJOs must have a usable public constructor. You can have an empty constructor or a constructor whose parameters match the fields (by name and type).
public final class DirectMessage implements com.example.barrechat192.data.entities.DirectMessage {
             ^
  Tried the following constructors but they failed to match:
  DirectMessage(java.lang.String,com.example.barrechat192.data.entities.User,com.example.barrechat192.data.entities.User,java.lang.String,long) -> [param:objectId -> matched field:objectId, param:author -> matched field:unmatched, param:recipient -> matched field:unmatched, param:content -> matched field:content, param:timestamp -> matched field:timestamp]C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\DirectMessage.java:10: error: Cannot find setter for field.
    private final java.lang.String _author = null;
                                   ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\DirectMessage.java:13: error: Cannot find setter for field.
    private final java.lang.String _recipient = null;
                                   ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\DirectMessage.java:17: error: Cannot find setter for field.
    private final java.lang.String objectId = null;
                                   ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\DirectMessage.java:25: error: Cannot find setter for field.
    private final java.lang.String content = null;
                                   ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\messages\DirectMessage.java:26: error: Cannot find setter for field.
    private final long timestamp = 0L;
                       ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\implementations\mapobjects\MapObject.java:10: error: The name "map_objects" is used by multiple entities or views: com.example.barrechat192.data.entities.implementations.mapobjects.MapObject, com.example.barrechat192.data.entities.implementations.mapobjects.MapObject
public final class MapObject implements com.example.barrechat192.data.entities.MapObject {
             ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\AppDatabase.java:8: error: The name "map_objects" is used by multiple entities or views: com.example.barrechat192.data.entities.implementations.mapobjects.MapObject, com.example.barrechat192.data.entities.implementations.mapobjects.MapObject
public abstract class AppDatabase extends androidx.room.RoomDatabase {
                ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\geocache\GeoTableWithMapObjects.java:12: error: Cannot find the child entity column `geohash` in com.example.barrechat192.data.entities.implementations.mapobjects.MapObject. Options: objectId, timestamp, thumbnailUrl, thumbnailPath, objectType, local, views, viewed, geoHash, latitude, longitude
    private final java.util.List<com.example.barrechat192.data.entities.implementations.mapobjects.MapObject> mapObjects = null;
                                                                                                              ^C:\Users\Anon\AndroidStudioProjects\Barrechat192\app\build\tmp\kapt3\stubs\debug\com\example\barrechat192\data\entities\geocache\GeoTableWithMapObjects.java:6: error: Entities and POJOs must have a usable public constructor. You can have an empty constructor or a constructor whose parameters match the fields (by name and type).

I also don't understand why I can inherit a val and change it to a var in a child class in Kotlin. That also seems to make the code work, changing the val to var in the entity class, but leaving it as a val in the interface.

Answer 1

I saw this message in your error log. The name "some object" is used by multiple entities or views.

I got a similar error like yours, Turns out, I accidentally added multiple Dto in my database entities.

@Database(
    entities = [
        FirstDto::class,
        SecondDto::class,
        SecondDto::class, //<--- This is my mistake.
        ThirdDto::class
    ], version = 2,
    exportSchema = false
)
abstract class MyDatabase : RoomDatabase() {
...
}