Database.java

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package org.openslx.imagemaster.db;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Collections;
import java.util.Properties;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.openslx.imagemaster.util.Util;

public class Database
{

   private static final Logger LOGGER = LogManager.getLogger( Database.class );
   private static final Queue<MysqlConnection> pool = new ConcurrentLinkedQueue<>();

   private static final Set<MysqlConnection> busyConnections = Collections.newSetFromMap( new ConcurrentHashMap<MysqlConnection, Boolean>() );

   private static final String host;
   private static final String dbname;
   private static final String user;
   private static final String password;

   static {
      // Load connection info from class (TODO: Make pretty)
      Properties properties = new Properties();
      try {
         final BufferedInputStream stream = new BufferedInputStream(
               new FileInputStream(
                     "config/mysql.properties" ) );
         properties.load( stream );
         stream.close();
      } catch ( FileNotFoundException e ) {
         LOGGER.fatal( "config/mysql.properties not found!" );
         System.exit( 1 );
      } catch ( IOException e ) {
         LOGGER.fatal( "Error reading from config/mysql.properties: " + e.getMessage() );
         System.exit( 1 );
      } catch ( Exception e ) {
         LOGGER.fatal( "Generic error loading mysql properties file." );
         e.printStackTrace();
         System.exit( 1 );
      }
      host = properties.getProperty( "host" );
      dbname = properties.getProperty( "db" );
      user = properties.getProperty( "user" );
      password = properties.getProperty( "password" );

      Util.notNullFatal( host, "host not set in mysql properties" );
      Util.notNullFatal( dbname, "db not set in mysql properties" );
      Util.notNullFatal( user, "user not set in mysql properties" );
      Util.notNullFatal( password, "password not set in mysql properties" );

      try {
         Class.forName( "org.mariadb.jdbc.Driver" ).newInstance();
      } catch ( Exception e1 ) {
         LOGGER.fatal( "Cannot get mysql JDBC driver", e1 );
         System.exit( 1 );
      }
   }

   public static MysqlConnection getConnection()
   {
      MysqlConnection con;
      for ( ;; ) {
         con = pool.poll();
         if ( con == null )
            break;
         if ( !con.isValid() ) {
            con.release();
            continue;
         }
         if ( !busyConnections.add( con ) )
            throw new RuntimeException( "Tried to hand out a busy connection!" );
         try {
            // By convention in our program we don't want auto commit
            con.setAutoCommit( false );
            return con;
         } catch ( SQLException e ) {
            con.release();
            continue;
         }
      }
      // No pooled connection
      if ( busyConnections.size() > 20 ) {
         LOGGER.warn( "Too many open MySQL connections. Possible connection leak!" );
         return null;
      }
      try {
         // Create fresh connection
         String uri = "jdbc:mariadb://" + host + "/" + dbname
               + "?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC"
               + "&characterSetResults=utf8&connectionCollation=utf8mb4_unicode_ci";
         Connection rawConnection = DriverManager.getConnection( uri,
               user, password );
         // By convention in our program we don't want auto commit
         rawConnection.setAutoCommit( false );
         // Wrap into our proxy
         con = new MysqlConnection( rawConnection );
         // Keep track of busy mysql connection
         if ( !busyConnections.add( con ) )
            throw new RuntimeException( "Tried to hand out a busy connection!" );
         return con;
      } catch ( SQLException e ) {
         LOGGER.info( "Failed to connect to local mysql server", e );
      }
      return null;
   }

   static void returnConnection( MysqlConnection connection )
   {
      if ( !busyConnections.remove( connection ) )
         throw new RuntimeException( "Tried to return a mysql connection to the pool that was not taken!" );
      pool.add( connection );
   }

   public static void printCharsetInformation()
   {
      LOGGER.info( "MySQL charset related variables:" );
      try ( MysqlConnection connection = Database.getConnection() ) {
         MysqlStatement stmt = connection.prepareStatement( "SHOW VARIABLES LIKE :what" );
         stmt.setString( "what", "char%" );
         ResultSet rs = stmt.executeQuery();
         while ( rs.next() ) {
            LOGGER.info( rs.getString( "Variable_name" ) + ": " + rs.getString( "Value" ) );
         }
         stmt.setString( "what", "collat%" );
         rs = stmt.executeQuery();
         while ( rs.next() ) {
            LOGGER.info( rs.getString( "Variable_name" ) + ": " + rs.getString( "Value" ) );
         }
      } catch ( SQLException e ) {
         LOGGER.error( "Query failed in Database.printCharsetInformation()", e );
      }
      LOGGER.info( "End of variables" );
   }

   public static void printDebug()
   {
      LOGGER.info( "Available: " + pool.size() );
      LOGGER.info( "Busy: " + busyConnections.size() );
   }

   public static boolean isDuplicateKeyException( SQLException e )
   {
      return e != null && e.getErrorCode() == 1062;
   }

}// end class