KeyIn
- The type of key used in the KeyValueSource
ValueIn
- The type of value used in the KeyValueSource
KeyOut
- The key type for mapped resultsValueOut
- The value type for mapped resultsAggregator
on IMap.
For general data processing, it is superseded by Hazelcast Jet.@Deprecated public interface Mapper<KeyIn,ValueIn,KeyOut,ValueOut> extends Serializable
The interface Mapper is used to build mappers for the Job
. Most mappers will only need to
implement this interface and the map(Object, Object, Context)
method to collect and emit needed
key-value pairs.
For more complex algorithms there is the possibility to implement the LifecycleMapper
interface and
override the LifecycleMapper.initialize(Context)
and LifecycleMapper.finalized(Context)
methods as well.
A simple mapper could look like the following example:
public class MyMapper extends Mapper<Integer, Integer, String, Integer> { public void map( Integer key, Integer value, Context<String, Integer> context ) { context.emit( String.valueOf( key ), value ); } }
If you want to know more about the implementation of MapReduce algorithms read the Google Whitepaper on MapReduce.
Modifier and Type | Method and Description |
---|---|
void |
map(KeyIn key,
ValueIn value,
Context<KeyOut,ValueOut> context)
Deprecated.
The map method is called for every single key-value pair in the bound
KeyValueSource instance
on this cluster node and partition.Due to its nature of a DataGrid, Hazelcast distributes values all over the cluster and so this method is executed on multiple servers at the same time. If you want to know more about the implementation of MapReduce algorithms read the Google Whitepaper on MapReduce. |
void map(KeyIn key, ValueIn value, Context<KeyOut,ValueOut> context)
KeyValueSource
instance
on this cluster node and partition.key
- key to mapvalue
- value to mapcontext
- Context to be used for emitting valuesCopyright © 2018 Hazelcast, Inc.. All rights reserved.