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package sql;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Collections;
import java.util.Queue;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
import models.Configuration;
import org.apache.log4j.Logger;
public class SQL {
private static final Logger LOGGER = Logger.getLogger(SQL.class);
/**
* Pool of available connections.
*/
private static final Queue<MysqlConnection> pool = new ConcurrentLinkedQueue<>();
/**
* Set of connections currently handed out.
*/
private static final Set<MysqlConnection> busyConnections = Collections.newSetFromMap(new ConcurrentHashMap<MysqlConnection, Boolean>());
static {
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
} catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
LOGGER.fatal("Cannot get mysql JDBC driver!", e);
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!");
return con;
}
// No pooled connection
if (busyConnections.size() > 20) {
LOGGER.warn("Too many open MySQL connections. Possible connection leak!");
return null;
}
try {
// Create fresh connection
Connection rawConnection = DriverManager.getConnection(Configuration.getDbUri(),
Configuration.getDbUsername(), Configuration.getDbPassword());
// 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);
}
}// end class
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