lang/csharp/src/apache/main/Schema/JsonHelper.cs

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
using System;
using System.Collections.Generic;
using System.Text;
using Newtonsoft.Json.Linq;
using Newtonsoft.Json;

namespace Avro
{
    class JsonHelper
    {
        /// <summary>
        /// Retrieves the optional string property value for the given property name from the given JSON object.
        /// This throws an exception if property exists but it is not a string.
        /// </summary>
        /// <param name="jtok">JSON object to read</param>
        /// <param name="field">property name</param>
        /// <returns>property value if property exists, null if property doesn't exist in the JSON object</returns>
        public static string GetOptionalString(JToken jtok, string field)
        {
            if (null == jtok) throw new ArgumentNullException("jtok", "jtok cannot be null.");
            if (string.IsNullOrEmpty(field)) throw new ArgumentNullException("field", "field cannot be null.");

            JToken child = jtok[field];
            if (null == child) return null;

            if (child.Type == JTokenType.String)
            {
                string value = child.ToString();
                return value.Trim('\"');
            }
            throw new SchemaParseException("Field " + field + " is not a string");
        }

        /// <summary>
        /// Retrieves the required string property value for the given property name from the given JSON object.
        /// </summary>
        /// <param name="jtok">JSON object to read</param>
        /// <param name="field">property name</param>
        /// <returns>property value</returns>
        public static string GetRequiredString(JToken jtok, string field)
        {
            string value = GetOptionalString(jtok, field);
            if (string.IsNullOrEmpty(value)) throw new SchemaParseException(string.Format("No \"{0}\" JSON field: {1}", field, jtok));
            return value;
        }

        /// <summary>
        /// Retrieves the required int property value for the given property name from the given JSON object.
        /// </summary>
        /// <param name="jtok">JSON object to read</param>
        /// <param name="field">property name</param>
        /// <returns>property value</returns>
        public static int GetRequiredInteger(JToken jtok, string field)
        {
            ensureValidFieldName(field);
            JToken child = jtok[field];
            if (null == child) throw new SchemaParseException(string.Format("No \"{0}\" JSON field: {1}", field, jtok));

            if (child.Type == JTokenType.Integer) return (int) child;
            throw new SchemaParseException("Field " + field + " is not an integer");
        }

        /// <summary>
        /// Retrieves the optional boolean property value for the given property name from the given JSON object.
        /// </summary>
        /// <param name="jtok">JSON object to read</param>
        /// <param name="field">property name</param>
        /// <returns>null if property doesn't exist, otherise returns property boolean value</returns>
        public static bool? GetOptionalBoolean(JToken jtok, string field)
        {
            if (null == jtok) throw new ArgumentNullException("jtok", "jtok cannot be null.");
            if (string.IsNullOrEmpty(field)) throw new ArgumentNullException("field", "field cannot be null.");

            JToken child = jtok[field];
            if (null == child) return null;

            if (child.Type == JTokenType.Boolean)
                return (bool)child;

            throw new SchemaParseException("Field " + field + " is not a boolean");
        }

        /// <summary>
        /// Writes JSON property name and value if value is not null
        /// </summary>
        /// <param name="writer">JSON writer</param>
        /// <param name="key">property name</param>
        /// <param name="value">property value</param>
        internal static void writeIfNotNullOrEmpty(JsonTextWriter writer, string key, string value)
        {
            if (string.IsNullOrEmpty(value)) return;
            writer.WritePropertyName(key);
            writer.WriteValue(value);
        }

        /// <summary>
        /// Checks if given name is not null or empty
        /// </summary>
        /// <param name="name"></param>
        private static void ensureValidFieldName(string name)
        {
            if (string.IsNullOrEmpty(name)) throw new ArgumentNullException("name");
        }
    }
}