# EventParameters.java

    /**
     *
     * Copyright 2009-2010 Rickard Öberg AB
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    package org.qi4j.library.eventsourcing.domain.source.helper;

    import org.json.JSONException;
    import org.json.JSONObject;
    import org.qi4j.library.eventsourcing.domain.api.DomainEventValue;

    /**
     * Utility class to pick out parameters by name or index as strings from a DomainEventValue
     */
    public class EventParameters
    {
        /**
         * Get the named parameter from an eventValue.
         *
         * @param eventValue eventValue with parameters
         * @param name  name of parameter
         * @return the parameter with the given name or null
         */
        public static String getParameter( DomainEventValue eventValue, String name )
        {
            String parametersJson = eventValue.parameters().get();
            try
            {
                JSONObject jsonObject = new JSONObject( parametersJson );
                return jsonObject.get( name ).toString();
            } catch (JSONException e)
            {
                return null;
            }
        }

        /**
         * Get parameter with given index.
         *
         * @param eventValue eventValue with parameters
         * @param idx   index of parameter
         * @return the parameter with the given index or null
         */
        public static String getParameter( DomainEventValue eventValue, int idx )
        {
            try
            {
                String parametersJson = eventValue.parameters().get();
                JSONObject jsonObject = new JSONObject( parametersJson );
                return jsonObject.get( "param" + idx ).toString();
            } catch (JSONException e)
            {
                return null;
            }
        }
    }