This guide describes the steps to using Apache Solr with Java, based on Docker container and Spring Boot. Apache Solr it is free to download from http://lucene.apache.org/solr/. SolrJ is an API that makes it easy for Java applications to talk to Solr. SolrJ hides a lot of the details of connecting to Solr and allows your application to interact with Solr with simple high-level methods. The center of SolrJ is the org.apache.solr.client.solrj package, which contains just five main classes. Begin by creating a SolrClient, which represents the Solr instance you want to use. Then send SolrRequests or SolrQuerys and get back SolrResponses. SolrClient is abstract, so to connect to a remote Solr instance, you'll actually create an instance of either HttpSolrClient, or CloudSolrClient. Both communicate with Solr via HTTP, the difference is that HttpSolrClient is configured using an explicit Solr URL, while CloudSolrClient is configured using the zkHost String for a SolrCloud cluster. https://cwiki.apache.org/confluence/display/solr/Using+SolrJ
Design patterns represent the best practices used by experienced object-oriented software developers. Design patterns are solutions to general problems that software developers faced during software development. These solutions were obtained by trial and error by numerous software developers over quite a substantial period of time.