DataStax Java Driver Mapper error on PrimitiveType cannot be cast to UserDefinedType

[Dongsheng Song]

Hi,

When I use DataStax Java Driver 4.7.2 with the Mapper, I got a class cast error:

java.lang.ClassCastException: com.datastax.oss.driver.internal.core.type.PrimitiveType cannot be cast to com.datastax.oss.driver.api.core.type.UserDefinedType

This error on the generated mapper MyCounterDaoImpl__MapperGenerated.java code:

UserDefinedType udtType = (UserDefinedType) boundStatementBuilder.getType("counter");

Here is the DAO:

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
@Entity
@CqlName("my_counter")
public class MyCounter {
    @PartitionKey
    private long id;
    private long counter;
}

and the Mapper:

@Dao
@DefaultNullSavingStrategy(SET_TO_NULL)
public interface MyCounterDao {
    @Query("UPDATE ${qualifiedTableId} SET counter = counter + :counter WHERE id= :id")
    void create(MyCounter counter);
}

Why the generated code treat the counter (long) as UserDefinedType ?

if (value != null) {
  UserDefinedType udtType = (UserDefinedType) boundStatementBuilder.getType("counter");
  UdtValue udtValue = udtType.newValue();
  myCounterHelper.set(value, udtValue,  NullSavingStrategy.DO_NOT_SET);
  boundStatementBuilder = boundStatementBuilder.setUdtValue("counter", udtValue);
} else if (nullSavingStrategy == NullSavingStrategy.SET_TO_NULL) {
  boundStatementBuilder = boundStatementBuilder.setUdtValue("counter", null);
}

Thanks,
Dongsheng

[Olivier Michallat]

Hi,

When you annotate a method with @Query, the mapper assumes that each parameter will match a query placeholder with the same name. Therefore the generated code attempts to fill :counter with MyCounter counter. Then it needs to decide how to convert the value. When it's a custom Java type annotated with @Entity, it assumes that the target CQL column is a UDT.

Obviously this doesn't  work here, what you want is to map counter.getId() to :id and counter.getCounter() to :counter. Explicitly dereferencing fields like that is not supported. What you'd really need is something like @Insert or @Update, but they don't work with counter columns.

Currently the only workaround is to pass the fields individually:

    @Query("UPDATE ${qualifiedTableId} SET counter = counter + :counter WHERE id= :id")

    void create(long id, long counter);

I'll admit that this is a bit of a letdown. This problem came up already, we have an open ticket to provide better support for counter tables: JAVA-2721.

Hope this helps,

Olivier Michallat

e. olivier....@datastax.com
w. www.datastax.com

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[Dongsheng Song]

Great, this workaround works for me.

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