sascha@14: package de.intevation.artifactdatabase;
sascha@14: 
sascha@14: import java.io.IOException;
sascha@14: import java.io.InputStream;
sascha@14: 
sascha@93: import java.util.Properties;
sascha@93: 
sascha@17: import org.apache.log4j.Logger;
sascha@17: 
sascha@14: /**
sascha@87:  * Singleton to provide SQL statement strings as key/value pairs.
sascha@87:  * This mechanism is used to encapsulate database specific SQL
sascha@87:  * dialects.
sascha@87:  *
ingo@80:  * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
sascha@14:  */
sascha@14: public final class SQL
sascha@14: {
sascha@17:     private static Logger logger = Logger.getLogger(SQL.class);
sascha@17: 
sascha@14:     private SQL() {
sascha@14:     }
sascha@14: 
sascha@14:     private static Properties statements;
sascha@14: 
sascha@87:     /**
sascha@87:      * Returns key/value pairs of SQL statements for the used database
sascha@87:      * backend.
sascha@87:      * The concrete set of SQL statements is determined by the
sascha@87:      * used JDBC database driver which is configured in conf.xml.
sascha@87:      * The class name of the driver is transformed by replacing
sascha@87:      * all '.' with '_' and lower case the resulting string.
sascha@87:      * The transformed string is used to load a properties file
sascha@87:      * in '/sql/' which should contain the statements.
sascha@87:      * Example:<br>
sascha@87:      * <code>org.postgresql.Driver</code> results in loading of
sascha@87:      * <code>/sql/org-postgresql-driver.properties</code>.
sascha@87:      * @return The key/value pairs of SQL statements.
sascha@87:      */
sascha@14:     public static final synchronized Properties getStatements() {
sascha@14:         if (statements == null) {
sascha@14:             statements = loadStatements();
sascha@14:         }
sascha@14:         return statements;
sascha@14:     }
sascha@14: 
sascha@14:     private static final Properties loadStatements() {
sascha@14:         String driver = Config.getStringXPath(
sascha@14:             DBConnection.DB_DRIVER, DBConnection.DEFAULT_DRIVER);
sascha@14: 
sascha@14:         Properties properties = new Properties();
sascha@14: 
sascha@14:         InputStream in = null;
sascha@14:         try {
sascha@47:             String res = "/sql/" + driver.replace('.', '-').toLowerCase()
sascha@14:                 + ".properties";
sascha@14:             in = SQL.class.getResourceAsStream(res);
sascha@14: 
sascha@14:             if (in == null) {
sascha@17:                 logger.warn("No SQL file for driver '" + driver + "' found.");
sascha@14:                 res = "/sql/" + DBConnection.DEFAULT_DRIVER.replace('.', '-').toLowerCase()
sascha@14:                     + ".properties";
sascha@14:                 if ((in = SQL.class.getResourceAsStream(res)) == null) {
sascha@17:                     logger.error("No SQL file found");
sascha@14:                 }
sascha@14:             }
sascha@14: 
sascha@14:             properties.load(in);
sascha@14:         }
sascha@14:         catch (IOException ioe) {
sascha@17:             logger.error(ioe.getLocalizedMessage(), ioe);
sascha@14:         }
sascha@14:         finally {
sascha@14:             if (in != null) {
sascha@14:                 try { in.close(); } catch (IOException ioe) {}
sascha@14:             }
sascha@14:         }
sascha@14: 
sascha@14:         return properties;
sascha@14:     }
sascha@14: 
sascha@87:     /**
sascha@87:      * Returns a particular SQL statement for a given key.
sascha@87:      * @param key The key of the statement.
sascha@87:      * @return The corresponing SQL statement or null if none
sascha@87:      * is found.
sascha@87:      */
sascha@14:     public static final String get(String key) {
sascha@14:         return getStatements().getProperty(key);
sascha@14:     }
sascha@14: }
sascha@87: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :