ExemplarServlet.java

package cz.incad.nkp.inprove;

import org.json.JSONObject;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

@WebServlet(value = "/exemplar/*")
public class ExemplarServlet extends HttpServlet {

    public static final Logger LOGGER = Logger.getLogger(SearchServlet.class.getName());
    public static final String solrDefaultHost = "localhost:8983/solr";
    public static final String space = "%20";
    public static final String exemplarPath = "exemplar/query";

    /**
     * Processes requests for HTTP <code>GET</code> method.
     * Creates solr query based on requested path and returns solr response.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        try {
            response.setContentType("application/json;charset=UTF-8");
            response.addHeader("Access-Control-Allow-Methods", "GET");
            PrintWriter out = response.getWriter();

            String id;
            String query = null;
            UriComponents uri;

            if (request.getPathInfo() == null) {
                throw new RuntimeException("Path does not exist.");
            }

            //example format of requestPathInfo: "/2081c9cc60d1101b53c4a0ce348195ee/dates"
            int firstSlashIndex = request.getPathInfo().indexOf("/") + 1;
            int secondSlashIndex = request.getPathInfo().indexOf("/", firstSlashIndex);
            id = request.getPathInfo().substring(firstSlashIndex, secondSlashIndex);

            //GET /api/exemplar/{id}/title-page-name
            //"Název na titulní straně"
            if (request.getPathInfo().contains("/title-page-name")) {
                query = "*:*&q.op=OR&indent=true&facet=true&rows=0&facet.field=nazev&facet.mincount=1&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/mutations
            //"Mutace"
            else if (request.getPathInfo().contains("/mutations")) {
                query = "*:*&q.op=OR&indent=true&facet=true&rows=0&facet.field=mutace&facet.mincount=1&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/publications
            //Vydání
            else if (request.getPathInfo().contains("publications")) {
                query = "*:*&q.op=OR&indent=true&facet=true&rows=0&facet.field=vydani&facet.mincount=1&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/mutation-markings
            //"Mutační vydání"
            else if (request.getPathInfo().contains("mutation-markings")) {
                query = "*:*&q.op=OR&indent=true&facet=true&rows=0&facet.field=oznaceni&facet.mincount=1&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/owners
            //"Vlastník"
            else if (request.getPathInfo().contains("owners")) {
                query = "*:*&q.op=OR&indent=true&facet=true&rows=0&facet.field=vlastnik&facet.mincount=1&vlastnik=&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/state
            //"Stav"
            else if (request.getPathInfo().contains("state")) {
                query = "*:*&q.op=OR&indent=true&facet=true&rows=0&facet.field=stav&facet.mincount=1&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/dates-range
            //"Rozsah datumu"
            else if (request.getPathInfo().contains("dates-range")) {
                query = "*:*&q.op=OR&indent=true&rows=0&stats=true&stats.field=datum_vydani_den&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/from-year/{year}
            //"Všechny záznamy z uvedeného roku"
            else if (request.getPathInfo().contains("from-year")) {
                //example format of requestPathInfo: "/2081c9cc60d1101b53c4a0ce348195ee/from-year/1995"
                int thirdSlashIndex = request.getPathInfo().indexOf("/", secondSlashIndex+1);
                String year = request.getPathInfo().substring(thirdSlashIndex+1, request.getPathInfo().length());

                query = "*:*&q.op=OR&indent=true&rows=10000&sort=datum_vydani_den" + space + "asc&fq=datum_vydani_den:{" + year + "0101" + space + "TO" + space + year + "1231}&fq=id_titul:\"" + id + "\"";
            }
            //GET /api/exemplar/{id}/years-range/{yearFrom-yearTo}
            //"Všechny záznamy z uvedeného rozpětí roků"
            else if (request.getPathInfo().contains("years-range")) {
                //example format of requestPathInfo: "/2081c9cc60d1101b53c4a0ce348195ee/years-range/1995-1997"
                int thirdSlashIndex = request.getPathInfo().indexOf("/", secondSlashIndex+1);
                int dashIndex = request.getPathInfo().lastIndexOf("-");
                String yearFrom = request.getPathInfo().substring(thirdSlashIndex+1, dashIndex);
                String yearTo = request.getPathInfo().substring(dashIndex+1, request.getPathInfo().length());

                query = "*:*&q.op=OR&indent=true&rows=10000&sort=datum_vydani_den" + space + "asc&fq=datum_vydani_den:%7B" + yearFrom + "0101" + space + "TO" + space + yearTo + "1231%7D&fq=id_titul:\"" + id + "\"";
            }
            else {
                throw new RuntimeException("Path does not exist.");
            }

            uri = createUri(query);

            LOGGER.log(Level.INFO, "requesting url {0}", uri.toString());
            Map<String, String> reqProps = new HashMap<>();
            reqProps.put("Content-Type", "application/json");
            reqProps.put("Accept", "application/json");
            try (InputStream inputStream = RESTHelper.inputStream(uri.toString(), reqProps)) {
                JSONObject result = removeUnnecessaryData(inputStream);

                String str = result.toString();
                InputStream is = new ByteArrayInputStream(str.getBytes());

                out.print(org.apache.commons.io.IOUtils.toString(is, StandardCharsets.UTF_8));
                is.close();
            }

        } catch (IOException ex) {
            LOGGER.log(Level.SEVERE, null, ex);
        }
    }

    /**
     * Creates correct URI for specific environment.
     * Passes given `query` to the URI.
     * @param query - solr query
     * @return correct URI
     */
    private UriComponents createUri(String query) {
        //TODO: Take into account that solr can run on different than default url
//        Options opts = Options.getInstance();
//        String solrhost = opts.getString("solrhost", solrDefaultHost);

        return UriComponentsBuilder.newInstance()
                .scheme("http")
                .host(solrDefaultHost)
                .path(exemplarPath)
                .query("q={keyword}")
                .buildAndExpand(query);
    }

    /**
     * Removes `responseHeader` from given `inputStream` representing solr response.
     * Also removes unnecessary facet attributes, leaving only relevant and filled data.
     * @param inputStream solr response in form of inputstream
     * @return JSONObject without `responseHeader`
     */
    private JSONObject removeUnnecessaryData(InputStream inputStream) {
        try (BufferedReader bR = new BufferedReader(new InputStreamReader(inputStream))) {
            String line = "";
            StringBuilder responseStrBuilder = new StringBuilder();

            while((line = bR.readLine()) != null){
                responseStrBuilder.append(line);
            }

            JSONObject result= new JSONObject(responseStrBuilder.toString());
            result.remove("responseHeader");

            if (result.has("facet_counts")) {
                JSONObject facet_counts = result.getJSONObject("facet_counts");

                facet_counts.remove("facet_intervals");
                facet_counts.remove("facet_queries");
                facet_counts.remove("facet_heatmaps");
                facet_counts.remove("facet_ranges");

                result.remove("facet_counts");
                result.append("facet_counts", facet_counts);
            }

            return result;
        }
        catch (IOException ioException) {
            throw new RuntimeException("Could not create buffered reader.");
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}