/* Copyright (c) 2009 Google Inc.
*
* 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.google.wave.api.impl;
import com.google.common.collect.Lists;
import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.InstanceCreator;
import com.google.gson.reflect.TypeToken;
import com.google.wave.api.Annotation;
import com.google.wave.api.Attachment;
import com.google.wave.api.BlipData;
import com.google.wave.api.Element;
import com.google.wave.api.JsonRpcResponse;
import com.google.wave.api.NonJsonSerializable;
import com.google.wave.api.OperationRequest;
import com.google.wave.api.Range;
import com.google.wave.api.BlipThread;
import com.google.wave.api.SearchResult;
import java.lang.reflect.Type;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
/**
* A factory to instantiate a {@link Gson} instance, with pre-registered type
* adapters for serializing and deserializing Wave API classes that are used
* as data transfer objects.
*/
public class GsonFactory {
public static final Type BLIP_MAP_TYPE = new TypeToken<Map<String, BlipData>>(){}.getType();
public static final Type PARTICIPANT_LIST_TYPE = new TypeToken<List<String>>(){}.getType();
public static final Type THREAD_MAP_TYPE = new TypeToken<Map<String, BlipThread>>(){}.getType();
public static final Type STRING_MAP_TYPE = new TypeToken<Map<String, String>>(){}.getType();
public static final Type OPERATION_REQUEST_LIST_TYPE = new TypeToken<List<OperationRequest>>(){}
.getType();
public static final Type JSON_RPC_RESPONSE_LIST_TYPE = new TypeToken<List<JsonRpcResponse>>(){}
.getType();
/** Additional type adapters. */
private final Map<Type, Object> customTypeAdapters = new LinkedHashMap<Type, Object>();
/**
* Registers a custom type adapter.
*
* @param type the type that will be handled by the given adapter.
* @param typeAdapter the adapter that performs the serialization and
* deserialization.
*/
public void registerTypeAdapter(Type type, Object typeAdapter) {
customTypeAdapters.put(type, typeAdapter);
}
/**
* Creates a {@link Gson} instance, with additional type adapters for these
* types:
* <ul>
* <li>{@link EventMessageBundle}</li>
* <li>{@link OperationRequest}</li>
* <li>{@link Element}</li>
* </ul>
*
* @return an instance of {@link Gson} with pre-registered type adapters.
*/
public Gson create() {
return create("");
}
/**
* Creates a {@link Gson} instance, with additional type adapters for these
* types:
* <ul>
* <li>{@link EventMessageBundle}</li>
* <li>{@link OperationRequest}</li>
* <li>{@link Element}</li>
* <li>{@link JsonRpcResponse}</li>
* </ul>
*
* @param opNamespace prefix that should be prepended to the operation during
* serialization.
* @return an instance of {@link Gson} with pre-registered type adapters.
*/
public Gson create(String opNamespace) {
ElementGsonAdaptor elementGsonAdaptor = new ElementGsonAdaptor();
GsonBuilder builder = new GsonBuilder()
.setExclusionStrategies(new NonSerializableExclusionStrategy())
.registerTypeAdapter(EventMessageBundle.class, new EventMessageBundleGsonAdaptor())
.registerTypeAdapter(OperationRequest.class, new OperationRequestGsonAdaptor(opNamespace))
.registerTypeAdapter(Element.class, elementGsonAdaptor)
.registerTypeAdapter(Attachment.class, elementGsonAdaptor)
.registerTypeAdapter(JsonRpcResponse.class, new JsonRpcResponseGsonAdaptor())
.registerTypeAdapter(Annotation.class, new AnnotationInstanceCreator())
.registerTypeAdapter(Range.class, new RangeInstanceCreator())
.registerTypeAdapter(BlipThread.class, new ThreadInstanceCreator())
.registerTypeAdapter(SearchResult.class, new SearchResultInstanceCreator())
.registerTypeAdapter(SearchResult.Digest.class, new SearchResultDigestInstanceCreator());
// Register custom type adapters.
for (Entry<Type, Object> entry : customTypeAdapters.entrySet()) {
builder.registerTypeAdapter(entry.getKey(), entry.getValue());
}
return builder.serializeNulls().create();
}
/**
* A strategy definition that excludes all fields that are annotated with
* {@link NonJsonSerializable}.
*/
private static class NonSerializableExclusionStrategy implements ExclusionStrategy {
@Override
public boolean shouldSkipClass(Class<?> clazz) {
return false;
}
@Override
public boolean shouldSkipField(FieldAttributes f) {
return f.getAnnotation(NonJsonSerializable.class) != null;
}
}
/**
* An instance creator that creates an empty {@link Annotation}.
*/
private static class AnnotationInstanceCreator implements InstanceCreator<Annotation> {
@Override
public Annotation createInstance(Type type) {
return new Annotation("", "", -1, -1);
}
}
/**
* An instance creator that creates an empty {@link Annotation}.
*/
private static class RangeInstanceCreator implements InstanceCreator<Range> {
@Override
public Range createInstance(Type type) {
return new Range(-1, -1);
}
}
/**
* An instance creator that creates an empty {@link BlipThread}.
*/
private static class ThreadInstanceCreator implements InstanceCreator<BlipThread> {
@Override
public BlipThread createInstance(Type type) {
return new BlipThread(null, -1, null, null);
}
}
/**
* An instance creator that creates an empty {@link SearchResult}.
*/
private static class SearchResultInstanceCreator implements InstanceCreator<SearchResult> {
@Override
public SearchResult createInstance(Type type) {
return new SearchResult("");
}
}
/**
* An instance creator that creates an empty {@link SearchResult.Digest}.
*/
private static class SearchResultDigestInstanceCreator implements InstanceCreator<SearchResult.Digest> {
@Override
public SearchResult.Digest createInstance(Type type) {
List<String> participants = Lists.newLinkedList();
return new SearchResult.Digest("", "", "", participants, -1, -1, -1);
}
}
}