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• DatabaseManager.java

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com.katujo.web.utils.DatabaseManager Maven / Gradle / Ivy

//Namespace
package com.katujo.web.utils;

//Java imports
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;


//Google imports
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

/**
 * Helps in database communication. 
 * @author Johan Hertz
 *
 */
public class DatabaseManager
{	
	//This map holds the data sources
	private final static Map dataSources = new ConcurrentHashMap();
	
	//The default data source look up that is used when calling methods without the data source specified
	private final String defaultLookup;	
	
	/**
	 * Create the object without a default data source look up set.
	 *
	 */
	public DatabaseManager() 
	{
		this.defaultLookup = null;
	}
	
	/**
	 * Create the object with the default data source look up set.
	 * @param defaultDataSource
	 */
	public DatabaseManager(String defaultDataSource)
	{
		this.defaultLookup = defaultDataSource;
	}
	
	/**
	 * Get the default data source.
	 * @return
	 * @throws Exception
	 */
	protected DataSource getDataSource() throws Exception
	{
		return getDataSource(defaultLookup);
	}
			
	/**
	 * Get the data source using the JNDI name.
	 * 

	 * On Tomcat this should be java:comp/env/DATA_SOURCE_NAME
	 * 
	 * @param name
	 * @return
	 * @throws Exception
	 */
	protected DataSource getDataSource(String lookup) throws Exception
	{
		//Try to get the data source
		try
		{
			//Get the data source from the map
			DataSource source = dataSources.get(lookup);
			
			//Create and add the data source if not set
			if(source == null)
			{							
				//Get the context objects 
				Context initCtx = new InitialContext();
				source = (DataSource) initCtx.lookup(lookup);
					
				//Add the source to the data sources 
				dataSources.put(lookup, source);
			}
			
			//Return the source
			return source;
		}
		
		//Failed
		catch(Exception ex)
		{
			throw new Exception("Failed to get the data source with lookup " + lookup, ex);
		}
	}
	
	/**
	 * Get a connection from the default data source. 
	 * 

	 * This connection must be explicitly closed by the caller.
	 * 
 
	 * @return
	 * @throws Exception
	 */
	public Connection getConnection() throws Exception
	{
		//Try to get a connection
		try {return getDataSource(defaultLookup).getConnection();}
		
		//Failed
		catch(Exception ex)
		{
			throw new Exception("Failed to get a connection", ex);
		}		
	}
	
	/**
	 * Get a connection from the named data source. 
	 * 

	 * This connection must be explicitly closed by the caller.
	 * 
	 * @param name
	 * @return
	 * @throws Exception
	 */
	public Connection getConnection(String name) throws Exception
	{
		//Try to get a connection
		try {return getDataSource(name).getConnection();}
		
		//Failed
		catch(Exception ex)
		{
			throw new Exception("Failed to get a connection", ex);
		}		
	}
	
	/**
	 * Load a JSON object from the database using the SQL.
	 * 

	 * If no result matched the query null will be returned.
	 * 
	 * @param sql
	 * @return
	 * @throws Exception
	 */
	protected JsonObject getObject(String sql) throws Exception
	{
		return getObject(sql, new Object[]{});
	}
	
	/**
	 * Load a JSON object from the database using the SQL and the parameter.
	 * 

	 * If no result matched the query null will be returned.
	 * 
	 * @param sql
	 * @param parameter
	 * @return
	 * @throws Exception
	 */	
	protected JsonObject getObject(String sql, Object parameter) throws Exception
	{
		return getObject(sql, new Object[]{parameter});
	}	
	
	/**
	 * Load a JSON object from the database using the SQL and the parameters.
	 * 

	 * If no result matched the query null will be returned.
	 * 
	 * @param sql
	 * @param parameters
	 * @return
	 * @throws Exception
	 */
	protected JsonObject getObject(String sql, Object[] parameters) throws Exception
	{
		//Fields
		Connection connection = null;
		PreparedStatement statement = null;
		ResultSet result = null;
		
		//Try to read data
		try
		{
			//Get a connection
			connection = getConnection();
			
			//Create the statement
			statement = connection.prepareStatement(sql);
			
			//Set the parameters if set 
			if(parameters != null)
				for(int i=0; i