During my talk at VoxxedVienna on using Hibernate Search with Elasticsearch earlier this week, there was an interesting question which I couldn’t answer right away:
"When running a full-text query with a projection of fields, is it possible to return the result as a list of POJOs rather than as a list of arrays of Object?"
The answer is: Yes, it is possible, result transformers are the right tool for this.
Let’s assume you want to convert the result of a projection query against the VideoGame entity shown in the talk into the following DTO (data transfer object):
public static class VideoGameDto {
private String title;
private String publisherName;
private Date release;
public VideoGameDto(String title, String publisherName, Date release) {
this.title = title;
this.publisherName = publisherName;
this.release = release;
}
// getters...
}This is how you could do it via a result transformer:
FullTextEntityManager ftem = ...;
QueryBuilder qb = ftem.getSearchFactory()
.buildQueryBuilder()
.forEntity( VideoGame.class )
.get();
FullTextQuery query = ftem.createFullTextQuery(
qb.keyword()
.onField( "tags" )
.matching( "round-based" )
.createQuery(),
VideoGame.class
)
.setProjection( "title", "publisher.name", "release" )
.setResultTransformer( new BasicTransformerAdapter() {
@Override
public VideoGameDto transformTuple(Object[] tuple, String[] aliases) {
return new VideoGameDto( (String) tuple[0], (String) tuple[1], (Date) tuple[2] );
}
} );
List<VideoGameDto> results = query.getResultList();I’ve pushed this example to the demo repo on GitHub.
There are also some ready-made implementations of the ResultTransformer interface which you might find helpful.
So be sure to check out its type hierarchy.
For this example I found it easiest to extend BasicTransformerAdapter and implement the transformTuple() method by hand.
To the person asking the question: Thanks, and I hope this answer is helpful to you!
