com.appenginefan.toolkit.common.PayloadBuilder.java Source code

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Here is the source code for com.appenginefan.toolkit.common.PayloadBuilder.java

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/*
 * Copyright (c) 2009 Jens Scheffler (appenginefan.com)
 * 
 * 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 com.appenginefan.toolkit.common;

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

/**
 * Utility class, used to concatenate a set of messages (given as strings)
 * into a single json object that can be parsed back on the receiving side.
 * The final result can be retrieved by using the toString() method.
 * This object is not threadsafe!
 * 
 * The returned object is a json map containing an array of messages
 * named "payload", plus an additional arbitrary amount of key/value pairs.
 * 
 */
class PayloadBuilder {

    /**
     * Name of the message list (payload)
     */
    public static final String TAG = "payload";

    private JSONObject object = new JSONObject();
    private JSONArray payload = new JSONArray();;
    private int size;

    /**
     * Constructor
     */
    public PayloadBuilder() {
        reset();
    }

    /**
     * Resets the builder, so that it can be reused
     */
    public PayloadBuilder reset() {
        object = new JSONObject();
        payload = new JSONArray();
        ;
        size = 0;
        return this;
    }

    /**
     * Adds a string message to the payload
     */
    public PayloadBuilder addPayload(String message) {
        payload.put(message);
        size++;
        return this;
    }

    public PayloadBuilder setProperty(String key, String value) {
        if (key.equals(TAG)) {
            throw new IllegalArgumentException("Illegal tag: " + key);
        }
        try {
            object.put(key, value);
        } catch (JSONException e) {
            throw new AssertionError("Cannot add as string to json object");
        }
        return this;
    }

    /**
     * Returns the amount of elements the builder currently contains.
     */
    public int size() {
        return size;
    }

    /**
     * Builds the result and returns it as a string
     */
    public String toString() {
        try {
            object.put(TAG, payload);
            return object.toString();
        } catch (JSONException e) {
            throw new AssertionError("Cannot add json array to json object");
        }
    }
}