16.2.3. Mapper and CDI
The
Mapper is invoked with appropriate input key/value pairs on an executing node, however JBoss Data Grid also provides a CDI injection for an input cache. The CDI injection can be used where additional data from the input cache is required in order to complete map transformation.
When the
Mapper is executed on a JBoss Data Grid executing node, the JBoss Data Grid CDI module provides an appropriate cache reference, which is injected to the executing Mapper. To use the JBoss Data Grid CDI module with Mapper:
- Declare a cache field in
Mapper. - Annotate the cache field
Mapperwith@org.infinispan.cdi.Input. - Annotate with mandatory
@Inject annotation.
For example:
public class WordCountCacheInjectedMapper implements Mapper<String, String, String, Integer> {
@Inject
@Input
private Cache<String, String> cache;
@Override
public void map(String key, String value, Collector<String, Integer> collector) {
//use injected cache if needed
StringTokenizer tokens = new StringTokenizer(value);
while (tokens.hasMoreElements()) {
for(String token : value.split("\\w")) {
collector.emit(token, 1);
}
}
}
