azkaban.util.json.JSONUtils.java Source code

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Here is the source code for azkaban.util.json.JSONUtils.java

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/*
 * Copyright 2010 LinkedIn, Inc
 * 
 * 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 azkaban.util.json;

import java.io.Reader;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONTokener;

/**
 * There are many implementations of JSON writers/parsers. This is to wrap them so we
 * aren't so sticky on any given implementation. Also wraps all the exception handling.
 * This isolates this dependency in case we want to change it in the future.
 * 
 * The current implementation uses org.json since it's simple and writes nice looking json.
 * 
 * @author Richard Park
 */
public class JSONUtils {

    /**
     * The constructor. Cannot construct this class.
     */
    private JSONUtils() {
    }

    /**
     * Takes a reader to stream the JSON string. The reader is not wrapped in a BufferReader
     * so it is up to the user to employ such optimizations if so desired.
     * 
     * The results will be Maps, Lists and other Java mapping of Json types (i.e. String, Number, Boolean).
     * 
     * @param reader
     * @return
     * @throws Exception
     */
    public static Map<String, Object> fromJSONStream(Reader reader) throws Exception {
        JSONObject jsonObj = new JSONObject(new JSONTokener(reader));
        Map<String, Object> results = createObject(jsonObj);

        return results;
    }

    /**
     * Converts a json string to Objects.
     * 
     * The results will be Maps, Lists and other Java mapping of Json types (i.e. String, Number, Boolean).
     * 
     * @param str
     * @return
     * @throws Exception
     */
    public static Map<String, Object> fromJSONString(String str) throws Exception {
        JSONObject jsonObj = new JSONObject(str);
        Map<String, Object> results = createObject(jsonObj);
        return results;
    }

    /**
     * Recurses through the json object to create a Map/List/Object equivalent.
     * 
     * @param obj
     * @return
     */
    @SuppressWarnings("unchecked")
    private static Map<String, Object> createObject(JSONObject obj) {
        LinkedHashMap<String, Object> map = new LinkedHashMap<String, Object>();

        Iterator<String> iterator = obj.keys();
        while (iterator.hasNext()) {
            String key = iterator.next();
            Object value = null;
            try {
                value = obj.get(key);
            } catch (JSONException e) {
                // Since we get the value from the key given by the JSONObject, 
                // this exception shouldn't be thrown.
            }

            if (value instanceof JSONArray) {
                value = createArray((JSONArray) value);
            } else if (value instanceof JSONObject) {
                value = createObject((JSONObject) value);
            }

            map.put(key, value);
        }

        return map;
    }

    /**
     * Recurses through the json object to create a Map/List/Object equivalent.
     * 
     * @param obj
     * @return
     */
    private static List<Object> createArray(JSONArray array) {
        ArrayList<Object> list = new ArrayList<Object>();
        for (int i = 0; i < array.length(); ++i) {
            Object value = null;
            try {
                value = array.get(i);
            } catch (JSONException e) {
                // Ugh... JSON's over done exception throwing.
            }

            if (value instanceof JSONArray) {
                value = createArray((JSONArray) value);
            } else if (value instanceof JSONObject) {
                value = createObject((JSONObject) value);
            }

            list.add(value);
        }

        return list;
    }

    /**
     * Creates a json string from Map/List/Primitive object.
     * 
     * @param obj
     * @return
     */
    public static String toJSONString(List<?> list) {
        JSONArray jsonList = new JSONArray(list);
        try {
            return jsonList.toString();
        } catch (Exception e) {
            return "";
        }
    }

    /**
     * Creates a json string from Map/List/Primitive object.
     * 
     * @param obj
     * @parm indent
     * @return
     */
    public static String toJSONString(List<?> list, int indent) {
        JSONArray jsonList = new JSONArray(list);
        try {
            return jsonList.toString(indent);
        } catch (Exception e) {
            return "";
        }
    }

    /**
     * Creates a json string from Map/List/Primitive object.
     * 
     * @param obj
     * @return
     */
    public static String toJSONString(Map<String, Object> obj) {
        JSONObject jsonObj = new JSONObject(obj);
        try {
            return jsonObj.toString();
        } catch (Exception e) {
            return "";
        }
    }

    /**
     * Creates a json pretty string from Map/List/Primitive object
     * 
     * @param obj
     * @param indent
     * @return
     */
    public static String toJSONString(Map<String, Object> obj, int indent) {
        JSONObject jsonObj = new JSONObject(obj);
        try {
            return jsonObj.toString(4);
        } catch (Exception e) {
            return "";
        }
    }
}