datasourceutils.java

一个关于Spring框架的示例应用程序,简单使用,可以参考.

			TransactionSynchronizationManager.registerSynchronization(new ConnectionSynchronization(conHolder, dataSource));
			conHolder.requested();
		}

		return con;
	}

	/**
	 * Prepare the given Connection with the given transaction semantics.
	 * @param con the Connection to prepare
	 * @param definition the transaction definition to apply
	 * @return the previous isolation level, if any
	 * @throws SQLException if thrown by JDBC methods
	 * @see #resetConnectionAfterTransaction
	 */
	public static Integer prepareConnectionForTransaction(Connection con, TransactionDefinition definition)
			throws SQLException {
		Assert.notNull(con, "No connection specified");

		// apply read-only
		if (definition.isReadOnly()) {
			try {
				if (logger.isDebugEnabled()) {
					logger.debug("Setting JDBC connection [" + con + "] read-only");
				}
				con.setReadOnly(true);
			}
			catch (Exception ex) {
				// SQLException or UnsupportedOperationException
				// -> ignore, it's just a hint anyway
				logger.debug("Could not set JDBC connection read-only", ex);
			}
		}

		// apply isolation level
		Integer previousIsolationLevel = null;
		if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) {
			if (logger.isDebugEnabled()) {
				logger.debug("Changing isolation level of JDBC connection [" + con + "] to " +
						definition.getIsolationLevel());
			}
			previousIsolationLevel = new Integer(con.getTransactionIsolation());
			con.setTransactionIsolation(definition.getIsolationLevel());
		}

		return previousIsolationLevel;
	}

	/**
	 * Reset the given Connection after a transaction,
	 * regarding read-only flag and isolation level.
	 * @param con the Connection to reset
	 * @param previousIsolationLevel the isolation level to restore, if any
	 * @see #prepareConnectionForTransaction
	 */
	public static void resetConnectionAfterTransaction(Connection con, Integer previousIsolationLevel) {
		Assert.notNull(con, "No connection specified");
		try {
			// reset transaction isolation to previous value, if changed for the transaction
			if (previousIsolationLevel != null) {
				if (logger.isDebugEnabled()) {
					logger.debug("Resetting isolation level of connection [" + con + "] to " + previousIsolationLevel);
				}
				con.setTransactionIsolation(previousIsolationLevel.intValue());
			}

			// reset read-only
			if (con.isReadOnly()) {
				if (logger.isDebugEnabled()) {
					logger.debug("Resetting read-only flag of connection [" + con + "]");
				}
				con.setReadOnly(false);
			}
		}
		catch (Exception ex) {
			logger.info("Could not reset JDBC connection after transaction", ex);
		}
	}

	/**
	 * Apply the current transaction timeout, if any,
	 * to the given JDBC Statement object.
	 * @param stmt the JDBC Statement object
	 * @param dataSource DataSource that the Connection came from
	 * @see java.sql.Statement#setQueryTimeout
	 */
	public static void applyTransactionTimeout(Statement stmt, DataSource dataSource) throws SQLException {
		Assert.notNull(stmt, "No statement specified");
		ConnectionHolder holder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);
		if (holder != null && holder.hasTimeout()) {
			stmt.setQueryTimeout(holder.getTimeToLiveInSeconds());
		}
	}

	/**
	 * Close the given Connection if necessary, i.e. if it is not bound to the thread
	 * and it is not created by a SmartDataSource returning shouldClose=false.
	 * @param con Connection to close if necessary
	 * (if this is null, the call will be ignored)
	 * @param dataSource DataSource that the Connection came from
	 * @see SmartDataSource#shouldClose
	 */
	public static void closeConnectionIfNecessary(Connection con, DataSource dataSource) {
		try {
			doCloseConnectionIfNecessary(con, dataSource);
		}
		catch (SQLException ex) {
			logger.error("Could not close JDBC connection", ex);
		}
	}

	/**
	 * Actually close a JDBC Connection for the given DataSource.
	 * Same as closeConnectionIfNecessary, but throwing the original SQLException.
	 * <p>Directly accessed by TransactionAwareDataSourceProxy.
	 * @param con Connection to close if necessary
	 * (if this is null, the call will be ignored)
	 * @param dataSource DataSource that the Connection came from
	 * @throws SQLException if thrown by JDBC methods
	 * @see #closeConnectionIfNecessary
	 * @see TransactionAwareDataSourceProxy
	 */
	protected static void doCloseConnectionIfNecessary(Connection con, DataSource dataSource) throws SQLException {
		if (con == null) {
			return;
		}

		ConnectionHolder conHolder = (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);
		if (conHolder != null && con == conHolder.getConnection()) {
			// It's the transactional Connection: Don't close it.
			conHolder.released();
			return;
		}
		
		// Leave the Connection open only if the DataSource is our
		// special data source, and it wants the Connection left open.
		if (!(dataSource instanceof SmartDataSource) || ((SmartDataSource) dataSource).shouldClose(con)) {
			logger.debug("Closing JDBC connection");
			con.close();
		}
	}


	/**
	 * Callback for resource cleanup at the end of a non-native-JDBC transaction
	 * (e.g. when participating in a JTA transaction).
	 */
	private static class ConnectionSynchronization extends TransactionSynchronizationAdapter {

		private final ConnectionHolder connectionHolder;

		private final DataSource dataSource;

		private ConnectionSynchronization(ConnectionHolder connectionHolder, DataSource dataSource) {
			this.connectionHolder = connectionHolder;
			this.dataSource = dataSource;
		}

		public int getOrder() {
			return CONNECTION_SYNCHRONIZATION_ORDER;
		}

		public void suspend() {
			TransactionSynchronizationManager.unbindResource(this.dataSource);
		}

		public void resume() {
			TransactionSynchronizationManager.bindResource(this.dataSource, this.connectionHolder);
		}

		public void beforeCompletion() {
			// Release Connection early if the holder is not open anymore
			// (i.e. not used by another resource like a Hibernate Session
			// that has its own cleanup via transaction synchronization),
			// to avoid issues with strict JTA implementations that expect
			// the close call before transaction completion.
			if (!this.connectionHolder.isOpen()) {
				TransactionSynchronizationManager.unbindResource(this.dataSource);
				closeConnectionIfNecessary(this.connectionHolder.getConnection(), this.dataSource);
			}
		}

		public void afterCompletion(int status) {
			// If we haven't closed the Connection in beforeCompletion,
			// close it now. The holder might have been used for other
			// cleanup in the meantime, for example by a Hibernate Session.
			if (TransactionSynchronizationManager.hasResource(this.dataSource)) {
				TransactionSynchronizationManager.unbindResource(this.dataSource);
				closeConnectionIfNecessary(this.connectionHolder.getConnection(), this.dataSource);
			}
		}
	}

}