Chapter 4. Data conversion

Read and write operations on remote caches via the Hot Rod endpoint use the client marshaller by default. Hot Rod provides a DataFormat API for Java clients that you can use to perform cache operations with different media type encodings and/or marshallers.

For example, to bypass all serialization in the Hot Rod client and read the byte[] array stored in the remote cache:

// Existing RemoteCache instance
RemoteCache<String, Pojo> remoteCache = ...

// IdentityMarshaller is a no-op marshaller
DataFormat rawKeyAndValues =
DataFormat.builder()
          .keyMarshaller(IdentityMarshaller.INSTANCE)
          .valueMarshaller(IdentityMarshaller.INSTANCE)
          .build();

// Creates a new instance of RemoteCache with the supplied DataFormat
RemoteCache<byte[], byte[]> rawResultsCache =
remoteCache.withDataFormat(rawKeyAndValues);

// Existing remote cache using ProtostreamMarshaller
RemoteCache<String, Pojo> protobufCache = ...

// Request values returned as JSON
// Use the UTF8StringMarshaller to convert UTF-8 to String
DataFormat jsonString =
DataFormat.builder()
          .valueType(MediaType.APPLICATION_JSON)
          .valueMarshaller(new UTF8StringMarshaller())
          .build();
RemoteCache<byte[], byte[]> rawResultsCache =
protobufCache.withDataFormat(jsonString);

In this example, Data Grid Server handles the data conversion and throws an exception if it does not support the specified media type.

DataFormat jsonNode =
DataFormat.builder()
          .valueType(MediaType.APPLICATION_JSON)
          .valueMarshaller(new CustomJacksonMarshaller()
          .build();

RemoteCache<String, JsonNode> jsonNodeCache =
remoteCache.withDataFormat(jsonNode);

Object xmlValue = remoteCache
      .withDataFormat(DataFormat.builder()
      .valueType(MediaType.APPLICATION_XML)
      .valueMarshaller(new UTF8StringMarshaller())
      .build())
      .get(key);

For example, the preceding get(key) call returns values such as:

<?xml version="1.0" ?><string>Hello!</string>

Embedded caches have a default request encoding of application/x-java-object and a storage encoding that corresponds to the media type that you configure for the cache. This means that Data Grid marshalls POJOs from the application to the storage encoding for the cache and then returns POJOs back to the application. In some complex scenarios you can use the AdvancedCache API to change the default conversion to and from POJOs to other encodings.

The following example uses the withMediaType() method to return values as application/json on demand.

DefaultCacheManager cacheManager = new DefaultCacheManager();

// Encode keys and values as Protobuf
ConfigurationBuilder cfg = new ConfigurationBuilder();
cfg.encoding().key().mediaType("application/x-protostream");
cfg.encoding().value().mediaType("application/x-protostream");

cacheManager.defineConfiguration("mycache", cfg.build());

Cache<Integer, Person> cache = cacheManager.getCache("mycache");

cache.put(1, new Person("John","Doe"));

// Use Protobuf for keys and JSON for values
Cache<Integer, byte[]> jsonValuesCache = (Cache<Integer, byte[]>) cache.getAdvancedCache().withMediaType("application/x-protostream", "application/json");

byte[] json = jsonValuesCache.get(1);

{
   "_type":"org.infinispan.sample.Person",
   "name":"John",
   "surname":"Doe"
}