JsonUtil.java

/*
 * Copyright 2013 the original author or authors.
 *
 * 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 io.jdev.miniprofiler.json;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;

/**
 * Utility class used for JSON serialization.
 */
public class JsonUtil {

    public static List<Map<String, Object>> mapList(List<? extends Jsonable> srcList) {
        if (srcList == null) {
            return null;
        }

        List<Map<String, Object>> dest = new ArrayList<Map<String, Object>>(srcList.size());
        for (Jsonable srcObject : srcList) {
            dest.add(srcObject != null ? srcObject.toMap() : null);
        }
        return dest;
    }

    public static String toJson(Jsonable src) {
        StringBuilder buf = new StringBuilder();
        mapToJsonBuffer(buf, src.toMap());
        return buf.toString();
    }

    private static void objectToJsonBuffer(StringBuilder buf, Object obj) {
        if (obj == null) {
            buf.append("null");
        } else if (obj instanceof Jsonable) {
            mapToJsonBuffer(buf, ((Jsonable) obj).toMap()); //
        } else if (obj instanceof Map) {
            @SuppressWarnings("unchecked")
            Map<String, Object> map = (Map<String, Object>) obj;
            mapToJsonBuffer(buf, map); //
        } else if (obj instanceof Collection) {
            collectionToJsonBuffer(buf, (Collection) obj);
        } else if (obj instanceof Number || obj instanceof Boolean) {
            buf.append(obj.toString());
        } else {
            // treat it like a string, regardless
            stringToJsonBuffer(buf, obj.toString());
        }
    }

    private static void stringToJsonBuffer(StringBuilder buf, String str) {
        if (str == null) {
            buf.append("null");
        } else {
            quote(str, buf);
        }
    }

    /**
     * Produce a string in double quotes with backslash sequences in all the
     * right places. A backslash will be inserted within </, allowing JSON
     * text to be delivered in HTML. In JSON text, a string cannot contain a
     * control character or an unescaped quote or backslash.
     *
     * This code copied from The Jettison project JSONObject class, also under
     * the Apcache 2.0 license.
     *
     * @param string A String
     * @param sb     buffer to append to
     */
    public static void quote(String string, StringBuilder sb) {
        char c = 0;
        int i;
        int len = string.length();
        String t;

        sb.append('"');
        for (i = 0; i < len; i += 1) {
            c = string.charAt(i);
            switch (c) {
                case '\\':
                case '"':
                    sb.append('\\');
                    sb.append(c);
                    break;
                case '/':
                    sb.append('\\');
                    sb.append(c);
                    break;
                case '\b':
                    sb.append("\\b");
                    break;
                case '\t':
                    sb.append("\\t");
                    break;
                case '\n':
                    sb.append("\\n");
                    break;
                case '\f':
                    sb.append("\\f");
                    break;
                case '\r':
                    sb.append("\\r");
                    break;
                default:
                    if (c < ' ') {
                        t = "000" + Integer.toHexString(c);
                        sb.append("\\u" + t.substring(t.length() - 4));
                    } else {
                        sb.append(c);
                    }
            }
        }
        sb.append('"');
    }

    private static void collectionToJsonBuffer(StringBuilder buf, Collection<?> src) {
        buf.append("[");
        boolean first = true;
        for (Object val : src) {
            if (first) {
                first = false;
            } else {
                buf.append(',');
            }
            objectToJsonBuffer(buf, val);
        }
        buf.append("]");
    }

    private static void mapToJsonBuffer(StringBuilder buf, Map<String, ?> src) {
        buf.append("{");
        boolean first = true;
        for (Map.Entry<String, ?> entry : src.entrySet()) {
            if (first) {
                first = false;
            } else {
                buf.append(',');
            }
            stringToJsonBuffer(buf, entry.getKey());
            buf.append(':');
            objectToJsonBuffer(buf, entry.getValue());
        }
        buf.append("}");
    }
}