edu.umass.cs.nio.JSONPacket.java Source code

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Here is the source code for edu.umass.cs.nio.JSONPacket.java

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/* Copyright (c) 2015 University of Massachusetts
 * 
 * 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.
 * 
 * Initial developer(s): V. Arun */
package edu.umass.cs.nio;

import java.io.UnsupportedEncodingException;
import java.util.Arrays;

import org.json.JSONException;
import org.json.JSONObject;

import edu.umass.cs.nio.interfaces.IntegerPacketType;

/**
 * @author V. Arun
 */

/* An abstract class that all json packets should extend. */
public abstract class JSONPacket {
    /**
     * JSON key for the integer packet type.
     */
    public static final String PACKET_TYPE = "type";
    protected /*final*/ int type;

    /**
     * @param t
     */
    public JSONPacket(IntegerPacketType t) {
        this.type = t.getInt();
    }

    /**
     * @param json
     * @throws JSONException
     */
    public JSONPacket(JSONObject json) throws JSONException {
        this.type = getPacketType(json);
    }

    /**
     * @return JSONObject corresponding to fields in classes extending this
     *         class.
     * @throws JSONException
     */
    protected abstract JSONObject toJSONObjectImpl() throws JSONException;

    /**
     * @return JSONObject corresponding to this class' (including subclasses)
     *         fields.
     * @throws JSONException
     */
    public JSONObject toJSONObject() throws JSONException {
        JSONObject json = toJSONObjectImpl();
        json.put(PACKET_TYPE, type);
        return json;
    }

    public String toString() {
        try {
            return toJSONObject().toString();
        } catch (JSONException je) {
            je.printStackTrace();
        }
        return null;
    }

    /* ********************* static helper methods below ****************** */

    /**
     * @param json
     * @return Integer packet type.
     * @throws JSONException
     */
    public static final Integer getPacketType(JSONObject json) throws JSONException {
        if (json.has(PACKET_TYPE))
            return json.getInt(PACKET_TYPE);
        else
            return null;
    }

    /**
     * Puts type into json.
     * 
     * @param json
     * @param type
     */
    public static final void putPacketType(JSONObject json, int type) {
        try {
            json.put(PACKET_TYPE, type);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    /**
     * Puts type.getInt() into json.
     * 
     * @param json
     * @param type
     */
    public static final void putPacketType(JSONObject json, IntegerPacketType type) {
        try {
            json.put(PACKET_TYPE, type.getInt());
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    /**
     * @param str
     * @return True if {@code str} could possibly (but not necessarily) be in
     *         JSON format. This sanity check is quicker compared to taking a
     *         JSONException hit.
     */
    public static final boolean couldBeJSON(String str) {
        return str.startsWith("{") || str.startsWith("[");
    }

    /**
     * @param str
     * @return True if str starts with "{"
     */
    public static final boolean couldBeJSONObject(String str) {
        return str.startsWith("{");
    }

    /**
     * @param str
     * @return True if str starts with "["
     */
    public static final boolean couldBeJSONArray(String str) {
        return str.startsWith("[");
    }

    /**
     * @param bytes
     * @return True if this {@code bytes} could be possibly (but not
     *         necessarily) be in JSON format assuming the default
     *         {@link MessageExtractor} encoding.
     */
    public static final boolean couldBeJSON(byte[] bytes) {
        String str;
        try {
            str = MessageExtractor.decode(Arrays.copyOf(bytes, 4));
            return str.startsWith("{") || str.startsWith("[");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return bytes[0] == '{' || bytes[0] == '[';
    }

    /**
     * @param bytes
     * @param offset 
     * @return True if this {@code bytes} could be possibly (but not
     *         necessarily) be in JSON format assuming the default
     *         {@link MessageExtractor} encoding.
     */
    public static final boolean couldBeJSON(byte[] bytes, int offset) {
        String str;
        try {
            str = MessageExtractor.decode(Arrays.copyOfRange(bytes, offset, offset + 4));
            return str.startsWith("{") || str.startsWith("[");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return bytes[offset] == '{' || bytes[offset] == '[';
    }

}