rocket.json.client.JsonSerializer.java Source code

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Here is the source code for rocket.json.client.JsonSerializer.java

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/*
 * Copyright Miroslav Pokorny
 *
 * 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 rocket.json.client;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import com.google.gwt.json.client.JSONArray;
import com.google.gwt.json.client.JSONNull;
import com.google.gwt.json.client.JSONNumber;
import com.google.gwt.json.client.JSONObject;
import com.google.gwt.json.client.JSONValue;

/**
 * This interface is implemented by all JsonSerializers that can map a JSONValue
 * to a java object and back.
 * 
 * <ul>
 * <li>All serializable objects must implement {@link JsonSerializable}</li>
 * <li>All primitive types and String are automatically serializable</li>
 * <li>Static and transient fields are skipped just like
 * {@link java.io.Serializable}</li>
 * <li>For {@link java.util.List}, {@link java.util.Set} or
 * {@link java.util.Map} fields a jsonSerializer-type </li>
 * <li>Map keys are assumed to always be {@link java.lang.String}
 * </ul>
 * 
 * This class should not be referenced in code and only exists as a convenient
 * base class for the JsonSerializerGenerator.
 * 
 * @author Miroslav Pokorny
 */
abstract public class JsonSerializer {

    /**
     * Deserializes the given jsonValue into a java object
     * 
     * @param jsonValue
     * @return The deserialized read object.
     */
    abstract public Object readObject(JSONValue jsonValue);

    public List<Object> readList(final JSONValue jsonValue) {
        final List<Object> list = new ArrayList<Object>();
        this.readCollection(jsonValue.isArray(), list);
        return list;
    }

    public Set<Object> readSet(final JSONValue jsonValue) {
        final Set<Object> set = new HashSet<Object>();
        this.readCollection(jsonValue.isArray(), set);
        return set;
    }

    protected void readCollection(final JSONArray jsonArray, final Collection collection) {
        if (null != jsonArray) {
            final int size = jsonArray.size();
            for (int i = 0; i < size; i++) {
                final JSONValue element = jsonArray.get(i);
                collection.add(this.readObject(element));
            }
        }
    }

    public Map<String, Object> readMap(final JSONValue jsonValue) {
        final Map<String, Object> map = new HashMap<String, Object>();
        if (null != jsonValue) {
            final JSONObject object = jsonValue.isObject();
            final Iterator<String> keys = object.keySet().iterator();
            while (keys.hasNext()) {
                final String key = (String) keys.next();
                final JSONValue value = (JSONValue) object.get(key);

                final Object mapValue = this.readObject(value);

                map.put(key, mapValue);
            }
        }
        return map;
    }

    /**
     * Sub classes must override this method to read all the properties from the
     * json value and set fields upon instance.
     * 
     * @param jsonValue
     * @param instance
     */
    protected void readFields(final JSONValue jsonValue, final Object instance) {
    }

    /**
     * Serializes a java object into a jsonObject
     * 
     * @param instance
     * @return A JSONValue holding the json form.
     */
    abstract public JSONValue writeJson(Object instance);

    public JSONValue writeJson(final Collection collection) {
        JSONValue jsonValue = null;
        if (null == collection) {
            jsonValue = JSONNull.getInstance();
        } else {
            final JSONArray array = new JSONArray();
            int i = 0;

            final Iterator iterator = collection.iterator();
            while (iterator.hasNext()) {
                final Object element = iterator.next();

                array.set(i, this.writeJson(element));
                i++;
            }

            jsonValue = array;
        }
        return jsonValue;
    }

    public JSONValue writeJson(final Map map) {
        JSONValue jsonValue = null;
        if (null == map) {
            jsonValue = JSONNull.getInstance();
        } else {
            final JSONObject object = new JSONObject();

            final Iterator entries = map.entrySet().iterator();
            while (entries.hasNext()) {
                final Map.Entry entry = (Map.Entry) entries.next();
                final String key = (String) entry.getKey();
                final Object element = entry.getValue();

                object.put(key, this.writeJson(element));
            }

            jsonValue = object;
        }
        return jsonValue;
    }

    /**
     * Sub classes must override this method to add all the fields from the
     * given instance to the json object.
     * 
     * @param instance
     * @param jsonObject
     */
    protected void writeFields(final Object instance, final JSONObject jsonObject) {
    }

    /**
     * Null safe method to retrieve the double value from a jsonValue which may
     * or may not be a JSONNumber. If its null or not a JSONNumber 0 is
     * returned.
     * 
     * @param jsonValue
     * @return
     */
    double readDouble(final JSONValue jsonValue) {
        double value = 0;

        while (true) {
            if (null == jsonValue) {
                break;
            }
            final JSONNumber number = jsonValue.isNumber();
            if (null == number) {
                break;
            }

            value = number.getValue();
            break;
        }

        return value;
    }
}