DatabaseNativeExceptionHandler.java

package ch.rgw.tools;

import static ch.rgw.tools.JdbcLink.DBFLAVOR_H2;
import static ch.rgw.tools.JdbcLink.DBFLAVOR_MYSQL;
import static ch.rgw.tools.JdbcLink.DBFLAVOR_POSTGRESQL;

import java.sql.SQLException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Natively handles SQL Exceptions if possible. E.g. if we try to update a database sometimes a
 * "column already available" exception might occur constantly preventing us from finishing the
 * update - although not necessary. This class provides advise to the question whether an exception
 * is really necessary to be thrown.
 */
public class DatabaseNativeExceptionHandler {
	
	private static Logger log = LoggerFactory.getLogger(DatabaseNativeExceptionHandler.class);
	
	/**
	 * Try to handle the thrown Exception considering the native Database implementation
	 * 
	 * @param dBFlavor
	 * @param e
	 * @return <code>true</code> if we can not mitigate the problem and an exception should be
	 *         thrown, else <code>false</code>
	 */
	public static boolean handleException(String dBFlavor, SQLException e){
		switch (dBFlavor) {
		case DBFLAVOR_MYSQL:
			return handleMysqlException(e);
		case DBFLAVOR_POSTGRESQL:
			return handlePostgresException(e);
		case DBFLAVOR_H2:
			return handleH2Exception(e);
		default:
			log.error("Unknown database flavor: " + dBFlavor);
			break;
		}
		return true;
	}
	
	// ----------- H2
	private static boolean handleH2Exception(SQLException e){
		return true;
	}
	
	// ----------- MYSQL
	public static final String MYSQL_ERRORCODE_TABLE_EXISTS = "42S01";
	public static final String MYSQL_ERRORCODE_DUPLICATE_COLUMN = "42S21";
	public static final String MYSQL_ERRORCODE_DUPLICATE_KEY_NAME = "42000";
	
	/**
	 * 
	 * @param e
	 * @return
	 * @see https://dev.mysql.com/doc/refman/5.5/en/error-messages-server.html
	 */
	private static boolean handleMysqlException(SQLException e){
		String sqlState = e.getSQLState();
		switch (sqlState) {
		case MYSQL_ERRORCODE_TABLE_EXISTS:
			log.info("Found table exists, mitigating error code " + sqlState + ": "
				+ e.getMessage());
			return false;
		case MYSQL_ERRORCODE_DUPLICATE_COLUMN:
			log.info("Found duplicate column, mitigating error code " + sqlState + ": "
				+ e.getMessage());
			return false;
		case MYSQL_ERRORCODE_DUPLICATE_KEY_NAME:
			log.info("Found duplicate key name, mitigating error code " + sqlState + ": "
				+ e.getMessage());
			return false;
		default:
		}
		return true;
	}
	
	// ----------- POSTGRES
	public static final String POSTGRES_ERRORCODE_DUPLICATE_COLUMN = "42701";
	public static final String POSTGRES_ERRORCODE_DUPLICATE_TABLE = "42P07";
	
	/**
	 * @param e
	 * @return
	 * @see http://www.postgresql.org/docs/9.1/static/errcodes-appendix.html
	 */
	private static boolean handlePostgresException(SQLException e){
		String sqlState = e.getSQLState();
		switch (sqlState) {
		case POSTGRES_ERRORCODE_DUPLICATE_TABLE:
		case POSTGRES_ERRORCODE_DUPLICATE_COLUMN:
			log.info("Found duplicate element, mitigating error code " + sqlState + ": "
				+ e.getMessage());
			return false;
		default:
		}
		
		return true;
	}
}