info.archinnov.achilles.annotations

Annotation Type Codec

@Retention(value=RUNTIME)
 @Target(value={FIELD,TYPE_USE,TYPE_PARAMETER})
 @Documented
public @interface Codec

Transform a custom Java type into one of native types supported by the Java driver
The Codec class provided should implement the Codec interface.

Let's consider the following codec transforming a Long to a String

 public class LongToString implements Codec<Long,String> {
 @Override
 public Class sourceType() {
 return Long.class;
 }

 @Override
 public Class targetType() {
 return String.class;
 }

 @Override
 public String encode(Long fromJava) throws AchillesTranscodingException {
 return fromJava.toString();
 }

 @Override
 public Long decode(String fromCassandra) throws AchillesTranscodingException {
 return Long.parseLong(fromCassandra);
 }
 }
 

Example of simple Long type to String type transformation

 @Column
 @Codec(LongToString.class)
 private Long longToString;

 

Example of List<Long> to List<String> transformation

 @Column
 private List<@Codec(LongToString.class) Long> listOfLongToString;

 

Example of Set<Long> to Set<String> transformation

 @Column
 private Set<@Codec(LongToString.class) Long> setOfLongToString;

 

Example of key Map transformation: Map<Long, Double> to Map<String, Double>

 @Column
 private Map<@Codec(LongToString.class) Long, Double> mapKeyTransformation;

 

Example of value Map transformation: Map<Integer, Long> to Map<Integer, String>

 @Column
 private Map<Integer,@Codec(LongToString.class)Long > mapValueTransformation;

 

Example of key/value Map transformation: Map<Long, Long> to Map<String, String>

 @Column
 private Map<@Codec(LongToString.class) Long, @Codec(LongToString.class) Long > mapKeyValueTransformation;
 

You can also have nested usage of @Codec. The nesting level can be arbitrary and does not matter

2-levels nesting

 @Column
 private Tuple2<String, Map<Integer, @Codec(LongToString.class) Long>> nested1Level
 

3-levels nesting

 @Column
 private Tuple2<String, Map<Integer, List<@Codec(LongToString.class) Long>>> nested2Level
 

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
Class<? extends Codec>	value Codec Implementation class.

Element Detail

value

public abstract Class<? extends Codec> value

Codec Implementation class. The provided Codec class should implement the Codec interface.