com.google.wave.api.impl.OperationRequestGsonAdaptor.java Source code

Introduction

Here is the source code for com.google.wave.api.impl.OperationRequestGsonAdaptor.java

Source

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.google.wave.api.impl;

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import com.google.wave.api.OperationRequest;
import com.google.wave.api.JsonRpcConstant.ParamsProperty;
import com.google.wave.api.JsonRpcConstant.RequestProperty;
import com.google.wave.api.OperationRequest.Parameter;

import java.lang.reflect.Type;
import java.util.Map.Entry;

/**
 * Custom serializer and deserializer that serializes and deserializes an
 * {@link OperationRequest}.
 *
 * @author mprasetya@google.com (Marcel Prasetya)
 */
public class OperationRequestGsonAdaptor
        implements JsonSerializer<OperationRequest>, JsonDeserializer<OperationRequest> {

    /**
     * A namespace that should be prepended to the operation method during
     * serialization.
     */
    private final String operationNamespace;

    /**
     * Constructor.
     */
    public OperationRequestGsonAdaptor() {
        this("");
    }

    /**
     * Constructor.
     *
     * @param operationNamespace namespace that should be prepended to the
     *     operation method during serialization.
     */
    public OperationRequestGsonAdaptor(String operationNamespace) {
        if (operationNamespace != null && !operationNamespace.isEmpty() && !operationNamespace.endsWith(".")) {
            operationNamespace += ".";
        }
        this.operationNamespace = operationNamespace;
    }

    @Override
    public JsonElement serialize(OperationRequest req, Type type, JsonSerializationContext ctx) {
        JsonObject object = new JsonObject();
        object.addProperty(RequestProperty.METHOD.key(), operationNamespace + req.getMethod());
        object.addProperty(RequestProperty.ID.key(), req.getId());

        JsonObject parameters = new JsonObject();
        for (Entry<ParamsProperty, Object> entry : req.getParams().entrySet()) {
            if (entry.getValue() != null) {
                parameters.add(entry.getKey().key(), ctx.serialize(entry.getValue()));
            }
        }
        object.add(RequestProperty.PARAMS.key(), parameters);
        return object;
    }

    @Override
    public OperationRequest deserialize(JsonElement json, Type type, JsonDeserializationContext ctx)
            throws JsonParseException {
        JsonObject jsonObject = json.getAsJsonObject();
        JsonObject parameters = jsonObject.getAsJsonObject(RequestProperty.PARAMS.key());

        OperationRequest request = new OperationRequest(jsonObject.get(RequestProperty.METHOD.key()).getAsString(),
                jsonObject.get(RequestProperty.ID.key()).getAsString(),
                getPropertyAsStringThenRemove(parameters, ParamsProperty.WAVE_ID),
                getPropertyAsStringThenRemove(parameters, ParamsProperty.WAVELET_ID),
                getPropertyAsStringThenRemove(parameters, ParamsProperty.BLIP_ID));

        for (Entry<String, JsonElement> parameter : parameters.entrySet()) {
            ParamsProperty parameterType = ParamsProperty.fromKey(parameter.getKey());
            if (parameterType != null) {
                Object object;
                if (parameterType == ParamsProperty.RAW_DELTAS) {
                    object = ctx.deserialize(parameter.getValue(), GsonFactory.RAW_DELTAS_TYPE);
                } else {
                    object = ctx.deserialize(parameter.getValue(), parameterType.clazz());
                }
                request.addParameter(Parameter.of(parameterType, object));
            }
        }

        return request;
    }

    /**
     * Returns a property of {@code JsonObject} as a {@link String}, then remove
     * that property.
     *
     * @param jsonObject the {@code JsonObject} to get the property from.
     * @param key the key of the property.
     * @return the property as {@link String}, or {@code null} if not found.
     */
    private static String getPropertyAsStringThenRemove(JsonObject jsonObject, ParamsProperty key) {
        JsonElement property = jsonObject.get(key.key());
        if (property != null) {
            jsonObject.remove(key.key());
            if (property.isJsonNull()) {
                return null;
            }
            return property.getAsString();
        }
        return null;
    }
}