Wednesday, May 13, 2015

SolrJ: Java API for Solr

Introduction


SolrJ is a Java client to access solr. SolrJ offers a java interface to add, update, and query the solr index.


HttpSolrServer


I use Spring to load this properties file:
solr.host   = 127.0.0.1
solr.port   = 8983
solr.core   = documents

# defaults to 0.  > 1 not recommended
solr.maxretries   = 1

# 5 seconds to establish TCP
solr.connectiontimeout  = 5000

# socket read timeout
solr.socketreadtimeout  = 50000

# max connections per host
solr.maxconnectionsperhost = 250

# max total connections
solr.maxtotalconnections = 100

# defaults to false
solr.followredirects  = false

# defaults to false
# Server side must support gzip or deflate for this to have any effect.
solr.allowcompression  = true

and to populate this method:
public static HttpSolrServer transform(String url, boolean allowcompression, Integer connectiontimeout, String core, boolean followredirects, Integer maxconnectionsperhost, Integer maxretries, Integer maxtotalconnections, Integer socketreadtimeout) throws AdapterValidationException {
 HttpSolrServer server = new HttpSolrServer(url);

 server.setMaxRetries(maxretries); 
 server.setConnectionTimeout(connectiontimeout); 
 
 /* Setting the XML response parser is only required for cross
    version compatibility and only when one side is 1.4.1 or
    earlier and the other side is 3.1 or later. */
 server.setParser(new XMLResponseParser()); 
 
 /* The following settings are provided here for completeness.
    They will not normally be required, and should only be used 
    after consulting javadocs to know whether they are truly required. */
 server.setSoTimeout(socketreadtimeout); 
 server.setDefaultMaxConnectionsPerHost(maxconnectionsperhost);
 server.setMaxTotalConnections(maxtotalconnections);
 server.setFollowRedirects(followredirects);
 server.setAllowCompression(allowcompression);

 return server;
}

By populating the method above with the values from the properties file, the system is able to work with a configured instance of the HttpSolrServer.


Query Snippets


This code will find the total records that mention the word "climate":
public static void main(String... args) throws Throwable {

 HttpSolrServer server = HttpSolrServerAdapter.transform();
 assertNotNull(server);

 SolrQuery q = new SolrQuery("text:climate");
 q.setRows(0); // don't actually request any data

 long total = server.query(q).getResults().getNumFound();
 logger.info("Total Records (total = %s)", total);

}


A reusable method for executing a query:
public static QueryResponse execute(
 String queryName, 
 HttpSolrServer server, 
 SolrQuery solrQuery) 
 throws BusinessException {
 try {

  QueryResponse queryResponse = server.query(solrQuery);
  logger.debug("Query Statistics " +
   "(query-name = %s, elapsed-time = %s, query-time = %s, status = %s, request-url = %s)",
    queryName, 
    queryResponse.getElapsedTime(), 
    queryResponse.getQTime(), 
    queryResponse.getStatus(), 
    queryResponse.getRequestUrl());

  SolrDocumentList solrDocumentList = queryResponse.getResults();
  logger.debug("Total Records " +
   "(query-name = %s, total = %s, query = %s)", 
    queryName, 
    StringUtils.format(solrDocumentList.size()), 
    solrQuery.toString());

  return queryResponse;

 } catch (SolrServerException e) {
  logger.error(e);
  throw new BusinessException("Unable to Query Server (query-name = %s, message = %s)", e.getMessage());
 }
}



References

  1. [Apache] SolrJ Wiki
  2. [Apache]  SolrJ Reference Guide

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