edu.cornell.mannlib.vitro.webapp.utils.solr.SolrResultsParser.java Source code

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Here is the source code for edu.cornell.mannlib.vitro.webapp.utils.solr.SolrResultsParser.java

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/* $This file is distributed under the terms of the license in /doc/license.txt$ */

package edu.cornell.mannlib.vitro.webapp.utils.solr;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.solr.client.solrj.response.QueryResponse;
import org.apache.solr.common.SolrDocument;
import org.apache.solr.common.SolrDocumentList;

/**
 * Parse this Solr response, creating a map of values for each document.
 * 
 * The Solr field names in the document are replaced by json field names in the
 * parsed results, according to the fieldMap.
 */
public class SolrResultsParser {
    private static final Log log = LogFactory.getLog(SolrResultsParser.class);

    private final QueryResponse queryResponse;
    private final Map<String, String> fieldNameMapping;

    public SolrResultsParser(QueryResponse queryResponse, FieldMap fieldMap) {
        this.queryResponse = queryResponse;
        this.fieldNameMapping = fieldMap.map();
    }

    /**
     * Parse the entire response into a list of maps.
     */
    public List<Map<String, String>> parse() {
        List<Map<String, String>> maps = new ArrayList<Map<String, String>>();

        if (queryResponse == null) {
            log.error("Query response for a search was null");
            return maps;
        }

        SolrDocumentList docs = queryResponse.getResults();
        if (docs == null) {
            log.error("Docs for a search was null");
            return maps;
        }
        log.debug("Total number of hits = " + docs.getNumFound());

        for (SolrDocument doc : docs) {
            maps.add(parseSingleDocument(doc));
        }

        return maps;
    }

    /**
     * Parse the response, accepting only those maps that are acceptable to the
     * filter, until we reach the maximum desired number of results (or until we
     * have parsed the entire response).
     */
    public List<Map<String, String>> parseAndFilterResponse(SolrResponseFilter filter, int maxNumberOfResults) {
        List<Map<String, String>> maps = new ArrayList<Map<String, String>>();

        if (queryResponse == null) {
            log.error("Query response for a search was null");
            return maps;
        }

        SolrDocumentList docs = queryResponse.getResults();
        if (docs == null) {
            log.error("Docs for a search was null");
            return maps;
        }
        log.debug("Total number of hits = " + docs.getNumFound());

        for (SolrDocument doc : docs) {
            Map<String, String> map = parseSingleDocument(doc);
            if (filter.accept(map)) {
                maps.add(map);
            }
            if (maps.size() >= maxNumberOfResults) {
                break;
            }
        }

        return maps;
    }

    /**
     * Create a map from this document, applying translation on the field names.
     */
    private Map<String, String> parseSingleDocument(SolrDocument doc) {
        Map<String, String> result = new HashMap<String, String>();
        for (String solrFieldName : fieldNameMapping.keySet()) {
            String jsonFieldName = fieldNameMapping.get(solrFieldName);

            result.put(jsonFieldName, parseSingleValue(doc, solrFieldName));
        }

        return result;
    }

    /**
     * Find a single value in the document
     */
    private String parseSingleValue(SolrDocument doc, String key) {
        Object rawValue = getFirstValue(doc.get(key));

        if (rawValue == null) {
            return "";
        }
        if (rawValue instanceof String) {
            return (String) rawValue;
        }
        return String.valueOf(rawValue);
    }

    /**
     * The result might be a list. If so, get the first element.
     */
    private Object getFirstValue(Object rawValue) {
        if (rawValue instanceof List<?>) {
            List<?> list = (List<?>) rawValue;
            if (list.isEmpty()) {
                return null;
            } else {
                return list.get(0);
            }
        } else {
            return rawValue;
        }
    }

}