org.commonjava.couch.io.json.CouchObjectListDeserializer.java Source code

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Here is the source code for org.commonjava.couch.io.json.CouchObjectListDeserializer.java

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/*******************************************************************************
 * Copyright 2011 John Casey
 * 
 * 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 org.commonjava.couch.io.json;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;

import org.commonjava.couch.db.model.CouchObjectList;
import org.commonjava.couch.model.CouchDocument;
import org.commonjava.web.json.ser.WebSerializationAdapter;

import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
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.reflect.TypeToken;

public class CouchObjectListDeserializer<T>
        implements JsonDeserializer<CouchObjectList<T>>, WebSerializationAdapter {

    private static final String ROWS = "rows";

    private static final String DOC_ELEMENT = "doc";

    private final Class<T> type;

    private final boolean allowMissing;

    private final TypeToken<CouchObjectList<T>> serType;

    public CouchObjectListDeserializer(final TypeToken<CouchObjectList<T>> serType, final Class<T> type) {
        this.serType = serType;
        this.type = type;
        this.allowMissing = false;
    }

    public CouchObjectListDeserializer(final TypeToken<CouchObjectList<T>> serType, final Class<T> type,
            final boolean allowMissing) {
        this.serType = serType;
        this.type = type;
        this.allowMissing = allowMissing;
    }

    @Override
    public CouchObjectList<T> deserialize(final JsonElement json, final Type typeOfT,
            final JsonDeserializationContext context) throws JsonParseException {
        final boolean useDocElement = CouchDocument.class.isAssignableFrom(type);

        final List<T> items = new ArrayList<T>();

        final JsonElement rowsRaw = json.getAsJsonObject().get(ROWS);
        if (rowsRaw == null) {
            throw new JsonParseException("Cannot find " + ROWS + " field within root object.");
        }

        final JsonArray rows = rowsRaw.getAsJsonArray();
        for (final JsonElement row : rows) {
            final JsonObject rowObj = row.getAsJsonObject();
            JsonElement data = rowObj;
            if (useDocElement) {
                data = rowObj.get(DOC_ELEMENT);
                if (data == null) {
                    if (allowMissing) {
                        continue;
                    }

                    throw new JsonParseException("Cannot find " + DOC_ELEMENT + " field within row: " + row
                            + "\nDid you access the view with the '?include_docs=true' query parameter?");
                }
            }

            final Object val = context.deserialize(data, type);
            if (val != null) {
                items.add(type.cast(val));
            }
        }

        return new CouchObjectList<T>(items);
    }

    @Override
    public void register(final GsonBuilder gsonBuilder) {
        gsonBuilder.registerTypeAdapter(serType.getType(), this);
    }

}