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package org.openslx.bwlp.sat.database;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
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 org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.openslx.bwlp.sat.util.Configuration;
public class Database {
private static final Logger LOGGER = LogManager.getLogger(Database.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 {
// Hack for some Java versions to register and instantiate the MySQL connection driver
Class.forName("com.mysql.cj.jdbc.Driver").newInstance();
} catch (InstantiationException | IllegalAccessException | ClassNotFoundException e) {
LOGGER.fatal("Cannot get mysql JDBC driver!", e);
System.exit(1);
}
}
/**
* Get a connection to the database. If there is a valid connection in the
* pool, it will be returned. Otherwise, a new connection is created. If
* there are more than 20 busy connections, <code>null</code> is returned.
*
* @return connection to database, or <code>null</code>
*/
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;
}
/**
* Called by a {@link MysqlConnection} when its <code>close()</code>-method
* is called, so the connection will be added to the pool of available
* connections again.
*
* @param connection
*/
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());
}
}// end class
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