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Util classes for a Java web application with a SQL database back end that communicates with clients using JSON.
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//Namespace
package com.katujo.web.utils;

//Java imports
import java.math.BigDecimal;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.concurrent.ConcurrentHashMap;

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

/**
 * JSON util methods that makes it easier to work with GSON/JSON in java.
 * @author Johan Hertz
 *
 */
public class JsonUtils
{
	//The map that holds the translation from SQL column format to JSON field name
	//
	private static final ConcurrentHashMap createJsonObjectColumnTranslator = new ConcurrentHashMap();	
	
	/**
	 * Get the member value as an object.
	 * @param element
	 * @param member
	 * @return
	 * @throws Exception
	 */	
	public static Object get(JsonElement element, String member) throws Exception
	{
		//Check if object
		if(!element.isJsonObject())
			throw new Exception("Element is not a JSON object");
		
		//Get the object value for the member
		return get(element.getAsJsonObject(), member);
	}
	
	/**
	 * Get the member value as an object.
	 * @param obj
	 * @param member
	 * @return
	 * @throws Exception
	 */
	public static Object get(JsonObject obj, String member) throws Exception
	{
		//The value is null
		if(obj.get(member) == null || obj.get(member).isJsonNull())
			return null;
		
		//Get the primitive
		JsonPrimitive primitive = obj.get(member).getAsJsonPrimitive();
		
		//Boolean
		if(primitive.isBoolean())
			return primitive.getAsBoolean();
		
		//Number/Double
		if(primitive.isNumber())
			return primitive.getAsDouble();
		
		//String
		if(primitive.isString())
			return primitive.getAsString();
		
		//Could not find a matching type
		throw new Exception("The member type is not regonised");
	}	
	
	
	/**
	 * Create a JSON array of JSON objects to hold the data in 
	 * the result set.
	 * @param result
	 * @return
	 * @throws Exception
	 */
	public static JsonArray createJsonArray(ResultSet result) throws Exception
	{
		//Try to create the data
		try
		{
			//Create the JSON array to hold the data
			JsonArray data = new JsonArray();
			
			//Read the result into the data
			while(result.next())
				data.add(createJsonObject(result));
			
			//Return the data
			return data;			
		}
		
		//Failed
		catch(Exception ex)
		{
			throw new Exception("Failed to create JSON array from result set", ex);
		}
	}
	
	/**
	 * Create a JSON object from a result set row.
	 * @param result
	 * @return
	 * @throws Exception
	 */
	public static JsonObject createJsonObject(ResultSet result) throws Exception
	{
		//Try to create the JSON object
		try
		{
			//Create the JSON object
			JsonObject obj = new JsonObject();
			
			//Get the meta data
			ResultSetMetaData meta = result.getMetaData();
				
			//Read the data into the object
			for(int i=0; i