Android Open Source - DKO Single Threaded Data Source

• Back to Database/orm  ↑

From Project

Back to project page DKO.

License

The source code is released under:

GNU Lesser General Public License

Java Source Code

package org.kered.dko.datasource;
/*from   w  w  w  . j a v  a  2  s  . c  o m*/
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Collection;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Logger;

import javax.sql.DataSource;

/**
 * This DataSource wraps another while enforcing a single threaded access model.
 * A new connection cannot be opened until the previously granted connection has been closed.
 * New calls to {@code getConnection()} will block until a timeout has been reached (at
 * which point a null is returned).
 * This is highly recommended as a wrapper around SQLite3 backed DataSources, as it cannot
 * handle multiple simultaneous connections.
 *
 * @author Derek Anderson
 */
public class SingleThreadedDataSource implements MatryoshkaDataSource {

  private final Lock lock = new ReentrantLock();
  private final DataSource ds;
  private final long timeout;
  private Connection conn = null;
  private static final Logger log = Logger.getLogger("org.kered.dko.datasource.SingleThreadedDataSource");

  /**
   * @param ds
   * @param timeout (in millis)
   */
  public SingleThreadedDataSource(final DataSource ds, final long timeout, boolean reuse) {
    this.ds = ds;
    this.timeout = timeout;
  }

  @Override
  public synchronized Connection getConnection() throws SQLException {
    long stopBy = System.currentTimeMillis() + timeout;
    try {
      while (System.currentTimeMillis() < stopBy) {
        if (lock.tryLock(100, TimeUnit.MILLISECONDS)) {
          if (!connOk(conn)) conn = ds.getConnection();
          return new UnClosableConnection(conn, new UnClosableConnection.CloseListener() {
            @Override
            public void wasClosed(final UnClosableConnection c) {
              lock.unlock();
            }
          });
        }
      }
      throw new RuntimeException("unable to aquire connection lock after "+ timeout +"ms");
    } catch (final InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  private static boolean connOk(Connection conn) {
    if (conn==null) return false;
    try {
      Statement stmt = conn.createStatement();
      ResultSet rs = stmt.executeQuery("select 1");
      rs.next();
      rs.getInt(1);
      stmt.close();
      return true;
    } catch (SQLException e) {
      e.printStackTrace();
      try {
        conn.close();
      } catch (SQLException e1) {
        e.printStackTrace();
      }
      conn = null;
      return false;
    }
  }

  @Override
  public Connection getConnection(final String username, final String password)
      throws SQLException {
    long stopBy = System.currentTimeMillis() + timeout;
    try {
      while (System.currentTimeMillis() < stopBy) {
        if (lock.tryLock(500, TimeUnit.MILLISECONDS)) {
          if (!connOk(conn)) conn = ds.getConnection(username, password);
          return new UnClosableConnection(conn, new UnClosableConnection.CloseListener() {
            @Override
            public void wasClosed(final UnClosableConnection c) {
              lock.unlock();
            }
          });
        }
      }
      throw new RuntimeException("unable to aquire connection lock after "+ timeout +"ms");
    } catch (final InterruptedException e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public PrintWriter getLogWriter() throws SQLException {
    return ds.getLogWriter();
  }

  @Override
  public void setLogWriter(final PrintWriter out) throws SQLException {
    ds.setLogWriter(out);
  }

  @Override
  public void setLoginTimeout(final int seconds) throws SQLException {
    ds.setLoginTimeout(seconds);
  }

  @Override
  public int getLoginTimeout() throws SQLException {
    return ds.getLoginTimeout();
  }

  @Override
  public <T> T unwrap(final Class<T> iface) throws SQLException {
    return ds.unwrap(iface);
  }

  @Override
  public boolean isWrapperFor(final Class<?> iface) throws SQLException {
    return ds.isWrapperFor(iface);
  }

  @Override
  public DataSource getPrimaryUnderlying() {
    return ds;
  }

  @Override
  public Collection<DataSource> getAllUnderlying() {
    final Collection<DataSource> ret = new ArrayList<DataSource>(1);
    ret.add(ds);
    return ret;
  }

  //@Override
  public Logger getParentLogger() throws SQLFeatureNotSupportedException {
    throw new SQLFeatureNotSupportedException();
  }

}

Java Source Code List

• Back to Database/orm  ↑