Can you avoid for loops with solrj? - sql

Question

I was curious if there was a way to avoid using loops when using SolrJ.
For example. If I were to use straight SQL, using an appropriate java library, I could return a Query result and caste it as a List and pass it on up to my view (in a webapp).
SolrJ (SolrQuery and QueryResponse) have no way of returning succinct lists it seems. This would imply I have to create an iterator to go through each return doc and get the value I want which isn't ideal.
Is there something I am missing here, is there away to avoid these seemingly useless loops?

Answer 1

The SOLRJ wiki give an example that does what you want:
https://wiki.apache.org/solr/Solrj#Reading_Data_from_Solr
Basically:
QueryResponse rsp = server.query( query );
SolrDocumentList docs = rsp.getResults();
List<Item> beans = rsp.getBeans(Item.class);
EDIT:
Based on your comments below, it appears what you want is a non-looping transform of the SOLR response (e.g. a map function in a functional language). Google's guava library provides something like this. My example below assumes that your SOLR response has a "name" field that you want to return a list of:
QueryResponse rsp = server.query(query);
SolrDocumentList docs = rsp.getResults();
List<String> names = Lists.transform(docs, new Function<String,SolrDocument>() {
#Override
public String apply(SolrDocument d) {
return (String)d.get("name");
}
});
Unfortunately, java does not support this style of programming very well, so the functional approach ends up being more verbose (and probably less clear) than a simple loop:
QueryResponse rsp = server.query(query);
SolrDocumentList docs = rs.getResults();
List<String> names = new ArrayList<String>();
for (SolrDocument d : docs) names.add(d.get("name"));