Database.java

package edu.uncc.cs.watsonsim;

import java.nio.FloatBuffer;
import java.sql.Array;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;


public class Database {
	private static Connection conn;
	
	public Database(Configuration env) {
		try {
			//Class.forName("org.sqlite.JDBC");
		    //Properties props = new Properties();
		    //props.put("busy_timeout", "30000");
			//conn = DriverManager.getConnection("jdbc:sqlite:/mnt/NCDS/sean/06Jan2014.3.watsonsim.db", props);
			
			// JDBC's SQLite uses autocommit (So commit() is redundant)
			// Furthermore, close() is a no-op as long as the results are commit()'d
			 
			
			//Class.forName("org.postgresql.Driver");
			if (conn == null) {
				conn = DriverManager.getConnection(env.getConfOrDie("jdbc_connection_string"));
				if (backend().startsWith("SQLite")) {
					//conn.createStatement().execute("PRAGMA journal_mode = WAL;");
					//conn.createStatement().execute("PRAGMA busy_timeout = 30000;");
					//conn.createStatement().execute("PRAGMA synchronous = OFF;");
				}
			}
			//conn.createStatement().execute("PRAGMA busy_timeout = 30000;");
			//System.err.println(conn.getClass().getName());

		} catch (SQLException e2) {
			e2.printStackTrace();
			throw new RuntimeException("Can't run without a database.");
		}
	}
	
	/** Simple wrapper for creating an SQL statement */
	public PreparedStatement prep(String sql) {
		PreparedStatement ps;
		try {
			ps = conn.prepareStatement(sql);
			ps.setFetchSize(100);
		} catch (SQLException e) {
			e.printStackTrace();
			throw new RuntimeException("Can't prepare an SQL statement \"" + sql + "\"");
		}
		return ps;
	}
	
	public void commit() {
		try {
			if (!conn.getAutoCommit()) {
				conn.commit();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	

	/**
	 * This is a convenience method for getting the first item after executing
	 * a prepared statement.
	 * 
	 * This is useful for statements ending in "RETURNING __;"
	 * 
	 * @param ps  The statement to run 
	 * @return  The ResultSet, moved forward one result
	 * @throws SQLException
	 */
	public ResultSet then(PreparedStatement ps) throws SQLException {
		ResultSet rs = ps.executeQuery();
		rs.next();
		return rs;
	}

	/**
	 * A simple delegate for creating Postgres arrays
	 */
	public Array createArrayOf(String typeName, Object[] elements) {
		try {
			return conn.createArrayOf(typeName, elements);
		} catch (SQLException e) {
			e.printStackTrace();
			throw new RuntimeException("Can't create an SQL array from \"" + elements + "\"");
		}
	}
	
	public String backend() {
		return conn.getClass().getSimpleName();
	}
}