datadb/compbio/cassandra/readers/CassandraReader.java

   1 package compbio.cassandra.readers;
   2
   3 import org.apache.log4j.Logger;
   4
   5 import com.datastax.driver.core.ResultSet;
   6 import com.datastax.driver.core.Session;
   7 import com.datastax.driver.core.exceptions.QueryExecutionException;
   8 import com.datastax.driver.core.exceptions.QueryValidationException;
   9
  10 import compbio.cassandra.CassandraNativeConnector;
  11
  12 /**
  13  * basic reader of the ProteoCache database. It depends on open
  14  * CassandraNativeConnector, which should provide an open session to the
  15  * ProteoCache DB (in the default constructor)
  16  *
  17  * @author as373024
  18  *
  19  */
  20 public class CassandraReader {
  21         protected static long earlestDate = 0;
  22         protected Session session;
  23         protected static Logger log = Logger.getLogger(CassandraNativeConnector.class);
  24
  25         /**
  26          * default constructor.
  27          */
  28         public CassandraReader() {
  29                 Session inis = CassandraNativeConnector.getSession();
  30                 setSession(inis);
  31         }
  32
  33         public void setSession(Session s) {
  34                 assert s != null;
  35                 session = s;
  36         }
  37
  38         /**
  39          * Basic query to the DB. The method throws exception if the input command
  40          * is not valid or if there is a problem with execution of the command
  41          *
  42          * @param command - reading CQL command
  43          * @return resulting outout of the command
  44          */
  45         protected ResultSet CassandraQuery(String command) {
  46                 try {
  47                         ResultSet results = session.execute(command);
  48                         return results;
  49                 } catch (QueryExecutionException e) {
  50                         String mess = "ProteoCache Cassandra DB interface: query execution exception...\n   Command: " + command;
  51                         System.out.println(mess);
  52                         log.error(mess);
  53                         log.error(e.getLocalizedMessage(), e.getCause());
  54                         return null;
  55                 } catch (QueryValidationException e) {
  56                         String mess = "CProteoCache Cassandra DB interface: query validation exception...\n   Command: " + command;
  57                         System.out.println(mess);
  58                         log.error(mess);
  59                         log.error(e.getLocalizedMessage(), e.getCause());
  60                         return null;
  61                 }
  62
  63         }
  64
  65         /**
  66          * finds the earliest date in the database
  67          *
  68          * @return the earliest date (long)
  69          */
  70         public static long earliestDate() {
  71                 earlestDate = CassandraNativeConnector.getEarliestDateInDB();
  72                 return earlestDate;
  73         }
  74
  75         /**
  76          * prepares an example of either job id or IP for the DB
  77          *
  78          * @param exampletype
  79          *            defines which example you need (an existing job from the DB -
  80          *            jobid, an IP - "ip")
  81          * @return a string representation of the requested example, if the example
  82          *         type is not known empty string is returned
  83          */
  84         public String getExample(String exampletype) {
  85                 if (exampletype.equals("jobid")) {
  86                         return "jp_NzBOJKo";
  87                 } else if (exampletype.equals("ip")) {
  88                         return "127.0.0.1";
  89                 }
  90                 return "";
  91         }
  92
  93 }