Determine Location of RiakObject during conflict resolution

Question

I am in the process of migrating my Java code from Riak Client 1.4 to Riak Client 2.0.

I'm storing a BinaryValue in Riak 2.0, encapsulated in a RiakObject. I need to provide my own ConflictResolver to deal with siblings, but in order to do that I need to pull in other data. This data is derived from the key of the stored object.

In Riak 1.4, I used IRiakObject, which exposed getKey(). RiakObject of Riak 2.0 does not offer this.

How is it possible to determine the Location (specifically the key) of the object during ConflictResolver.resolve(List<RiakObject> siblings)?

Answer 1

Not sure if this is the best approach, but it seems to work:

1. Create a POJO as a container for the binary data. Annotate a String field with @RiakKey:

   public class Chunk {
   
       @RiakKey
       public String   chunkId;
   
       public byte[]   data;
   }
   

2. Create a custom converter:

   import com.basho.riak.client.api.convert.ConversionException;
   import com.basho.riak.client.api.convert.Converter;
   import com.basho.riak.client.core.util.BinaryValue;
   public class ChunkConverter extends Converter<Chunk> {
   
       public ChunkConverter() {
           super(Chunk.class);
       }
   
       public Chunk toDomain(BinaryValue val, String contentType) throws ConversionException {
           Chunk chunk = newDomainInstance();
           chunk.data = val.getValue();
       }
   
       public ContentAndType fromDomain(Chunk chunk) throws ConversionException {
           return new ContentAndType(BinaryValue.unsafeCreate(chunk.data), "application/octet-stream");
       }
   }
   

3. Register the converter from #2 for the class from #1:

   ConverterFactory.getInstance().registerConverterForClass(Chunk.class, new ChunkConverter());
   

4. Create a conflict resolver for the class from #1:

   public class ChunkConflictResolver implements ConflictResolver<Chunk> {
   
       public Chunk resolve(List<Chunk> siblings) throws UnresolvedConflictException {
           if (siblings == null) {
               return null;
           }
           Chunk oneChunk = siblings.get(0);
           // finally, the key!
           String key = oneChunk.chunkId;
           ...
       }
   }
   

5. Register the new conflict resolver from #4 for the class from #1:

   ConflictResolverFactory.getInstance().registerConflictResolver(Chunk.class, new ChunkResolver());
   

6. When fetching the object from Riak, specify the class from #1 as type of value:

   Location loc = new Location(...);
   FetchValue op = new FetchValue.Builder(loc).build();
   Chunk chunk = riakClient.execute(op).getValue(Chunk.class);
   

During the conversion, the context of the object is transferred, observing the annotations. The custom converter only needs to transfer the value-part of the data.