GenericDao.java

/*******************************************************************************
 * Copyright (c) 2011 Softberries Krzysztof Grajek.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     Softberries Krzysztof Grajek - initial API and implementation
 ******************************************************************************/
package com.softberries.klerk.dao;

import java.io.File;
import java.net.URL;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;

/**
 * Common functionality for data access objects
 * within Klerk application
 * 
 * @author kris
 *
 */
public abstract class GenericDao<T> {
	
	/**
	 * Pass specific {@link filePath} to the dao
	 * @param filePath
	 */
	public GenericDao(String filePath){
		this.filePath = filePath;
	}
	/**
	 * Pass specific {@link filePath} to the dao using
	 * a File object
	 * @param dbFile
	 */
	public GenericDao(File dbFile){
		this.filePath = dbFile.getAbsolutePath();
	}
	/**
	 * Database connection object
	 */
	protected Connection conn = null;
	/**
	 * Keeps the current prepared statement reference
	 */
	protected PreparedStatement st = null;
	/**
	 * Keeps the current {@code ResultSet} reference
	 */
	protected ResultSet generatedKeys = null;
	/**
	 * Utility object from Apache library 
	 * allowing convertion between {@code ResultSet}
	 * and specific Transfer Object
	 */
	protected QueryRunner run = null;
	
	/**
	 * Database file location when using file based datastore
	 */
	protected String filePath = null;
	
	/**
	 * Initializes connection to the database
	 * 
	 * @throws ClassNotFoundException
	 * @throws SQLException
	 */
	public void init() throws ClassNotFoundException, SQLException{
		run = new QueryRunner();
		Class.forName("org.h2.Driver");
		conn = DriverManager.getConnection("jdbc:h2:"+this.filePath, "sa", "");
		conn.setAutoCommit(false);
	}
	/**
	 * Closes all resources after execution
	 * 
	 * @param con {@code Connection} object
	 * @param stm {@code PreparedStatement} object
	 * @param gk {@code ResultSet} object
	 * @throws SQLException
	 */
	protected void close(Connection con, PreparedStatement stm,
			ResultSet gk) throws SQLException {
		if(gk != null){
			gk.close();
		}
		if(stm != null){
			stm.close();
		}
		if(con != null){
			con.close();
		}
	}
	/**
	 * Finds all records and convert it to the specific type
	 * 
	 * @return {@code List<T>} list of specific objects created from {@code ResultSet}
	 *  
	 * @throws SQLException
	 */
	public abstract List<T> findAll()  throws SQLException;
	/**
	 * Finds object of type <T> in the database
	 * 
	 * @param id
	 * @return
	 * @throws SQLException
	 */
	public abstract T find(Long id) throws SQLException;
	/**
	 * Adds new record to the database based on the Object of type T
	 * @param t
	 * @throws SQLException
	 */
	public abstract void create(T t) throws SQLException;
	/**
	 * Updates single record in the database
	 * @param t
	 * @throws SQLException
	 */
	public abstract void update(T t) throws SQLException;
	/**
	 * Deletes single record in the database
	 * @param id
	 * @throws SQLException
	 */
	public abstract void delete(Long id) throws SQLException;
	/**
	 * Deletes all records in a table corresponding the type T
	 * @throws SQLException
	 */
	public abstract void deleteAll() throws SQLException;
}