Database.java

package org.hello.tomcat.data;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class Database {
	
	private final String connectionUrl; 
	private Connection connection = null;
	
	public static Database create(String connectionUrl) throws ClassNotFoundException {
		return new Database(connectionUrl);
	}
	
	public Database(String connectionUrl) throws ClassNotFoundException {
		Class.forName(org.sqlite.JDBC.class.getName());
		this.connectionUrl = connectionUrl;
	}
	
	public Database connect() throws SQLException {
		this.connection = DriverManager.getConnection(this.connectionUrl);
		return this;
	}
	
	public Database close() throws SQLException {
		if (this.connection != null && !this.connection.isClosed())
			this.connection.close();
		return this;
	}
	
	public <T> List<T> query (String sql, Factory<T> factory) throws Exception {
		final Statement statement = this.connection.createStatement();
		final ResultSet resultSet = statement.executeQuery(sql);
		
		final List<T> list = new ArrayList<T>();
		while(resultSet.next()) {
			list.add(factory.create(resultSet));
		}
		return list;
	}
	
	public void execute(String sql) throws SQLException {
		final Statement statement = this.connection.createStatement();
		statement.execute(sql);
		statement.close();
	}
	
	public void execute(String... sql) throws SQLException {
		final Statement statement = this.connection.createStatement();
		for(String s : sql) {
			statement.addBatch(s);
		}
		statement.executeBatch();
		statement.close();
	}
}

Factory.java

package org.hello.tomcat.data;

import java.sql.ResultSet;

public interface Factory<T> {
	public T create(ResultSet resultSet) throws Exception;
}