Spring Framework example source code file (DatabaseStartupValidator.java)

This example Spring Framework source code file (DatabaseStartupValidator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

connection, database, database, databasestartupvalidator, datasource, default_interval, default_interval, default_timeout, default_timeout, illegalargumentexception, initializingbean, jdbc, sql, sqlexception, sqlexception, statement

The Spring Framework DatabaseStartupValidator.java source code

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.support;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.InitializingBean;
import org.springframework.jdbc.CannotGetJdbcConnectionException;

/**
 * Bean that checks if a database has already started up. To be referenced
 * via "depends-on" from beans that depend on database startup, like a Hibernate
 * SessionFactory or custom data access objects that access a DataSource directly.
 *
 * <p>Useful to defer application initialization until a database has started up.
 * Particularly appropriate for waiting on a slowly starting Oracle database.
 *
 * @author Juergen Hoeller
 * @since 18.12.2003
 */
public class DatabaseStartupValidator implements InitializingBean {

	public static final int DEFAULT_INTERVAL = 1;

	public static final int DEFAULT_TIMEOUT = 60;


	protected final Log logger = LogFactory.getLog(getClass());

	private DataSource dataSource;

	private String validationQuery;

	private int interval = DEFAULT_INTERVAL;

	private int timeout = DEFAULT_TIMEOUT;


	/**
	 * Set the DataSource to validate.
	 */
	public void setDataSource(DataSource dataSource) {
		this.dataSource = dataSource;
	}

	/**
	 * Set the SQL query string to use for validation.
	 */
	public void setValidationQuery(String validationQuery) {
		this.validationQuery = validationQuery;
	}

	/**
	 * Set the interval between validation runs (in seconds).
	 * Default is 1.
	 */
	public void setInterval(int interval) {
		this.interval = interval;
	}

	/**
	 * Set the timeout (in seconds) after which a fatal exception
	 * will be thrown. Default is 60.
	 */
	public void setTimeout(int timeout) {
		this.timeout = timeout;
	}


	/**
	 * Check whether the validation query can be executed on a Connection
	 * from the specified DataSource, with the specified interval between
	 * checks, until the specified timeout.
	 */
	public void afterPropertiesSet() {
		if (this.dataSource == null) {
			throw new IllegalArgumentException("dataSource is required");
		}
		if (this.validationQuery == null) {
			throw new IllegalArgumentException("validationQuery is required");
		}

		try {
			boolean validated = false;
			long beginTime = System.currentTimeMillis();
			long deadLine = beginTime + this.timeout * 1000;
			SQLException latestEx = null;

			while (!validated && System.currentTimeMillis() < deadLine) {
				Connection con = null;
				Statement stmt = null;
				try {
					con = this.dataSource.getConnection();
					stmt = con.createStatement();
					stmt.execute(this.validationQuery);
					validated = true;
				}
				catch (SQLException ex) {
					latestEx = ex;
					logger.debug("Validation query [" + this.validationQuery + "] threw exception", ex);
					float rest = ((float) (deadLine - System.currentTimeMillis())) / 1000;
					if (rest > this.interval) {
						logger.warn("Database has not started up yet - retrying in " + this.interval +
								" seconds (timeout in " + rest + " seconds)");
					}
				}
				finally {
					JdbcUtils.closeStatement(stmt);
					JdbcUtils.closeConnection(con);
				}

				if (!validated) {
					Thread.sleep(this.interval * 1000);
				}
			}

			if (!validated) {
				throw new CannotGetJdbcConnectionException(
						"Database has not started up within " + this.timeout + " seconds", latestEx);
			}

			float duration = (System.currentTimeMillis() - beginTime) / 1000;
			if (logger.isInfoEnabled()) {
				logger.info("Database startup detected after " + duration + " seconds");
			}
		}
		catch (InterruptedException ex) {
			// Re-interrupt current thread, to allow other threads to react.
			Thread.currentThread().interrupt();
		}
	}

}