com.goodow.realtime.server.rpc.DeltaHandler.java Source code

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Here is the source code for com.goodow.realtime.server.rpc.DeltaHandler.java

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/*
 * Copyright 2012 Goodow.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.goodow.realtime.server.rpc;

import com.goodow.realtime.channel.constant.Constants.Params;
import com.goodow.realtime.server.model.Delta;
import com.goodow.realtime.server.model.DeltaSerializer;
import com.goodow.realtime.server.model.ObjectId;

import com.google.common.collect.ImmutableList;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.google.inject.Inject;
import com.google.walkaround.slob.server.AccessDeniedException;
import com.google.walkaround.slob.server.SlobFacilities;
import com.google.walkaround.slob.server.SlobNotFoundException;
import com.google.walkaround.slob.server.SlobStore;
import com.google.walkaround.slob.server.SlobStore.HistoryResult;
import com.google.walkaround.util.server.servlet.AbstractHandler;
import com.google.walkaround.util.server.servlet.BadRequestException;

import java.io.IOException;
import java.util.List;
import java.util.logging.Logger;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Used by the client to notify the server of connection to an object at a specific revision, or to
 * refresh a channel.
 */
public class DeltaHandler extends AbstractHandler {

    @SuppressWarnings("unused")
    private static final Logger log = Logger.getLogger(DeltaHandler.class.getName());

    private static JsonArray serializeDeltas(long startVersion, List<Delta<String>> entries) {
        JsonArray history = new JsonArray();
        int index = 0;
        for (Delta<String> data : entries) {
            history.add(DeltaSerializer.dataToClientJson(data, startVersion + index + 1));
            index++;
        }
        return history;
    }

    @Inject
    SlobFacilities slobFacilities;

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        String id = requireParameter(req, Params.ID);
        JsonObject toRtn = new JsonObject();
        try {
            Long startRev = Long.parseLong(requireParameter(req, Params.START_REVISION));
            String endRevString = optionalParameter(req, Params.END_REVISION, null);
            Long endRev = endRevString == null ? null : Long.parseLong(endRevString);
            fetchDeltas(toRtn, new ObjectId(id), startRev - 1, endRev);
        } catch (SlobNotFoundException e) {
            throw new BadRequestException("Object not found or access denied", e);
        } catch (AccessDeniedException e) {
            throw new BadRequestException("Object not found or access denied", e);
        } catch (NumberFormatException nfe) {
            throw new BadRequestException("Parse error", nfe);
        }

        RpcUtil.writeJsonResult(req, resp, toRtn.toString());
    }

    boolean fetchDeltas(JsonObject obj, ObjectId key, long version, Long endVersion)
            throws IOException, SlobNotFoundException, AccessDeniedException {
        SlobStore store = slobFacilities.getSlobStore();
        HistoryResult history = store.loadHistory(key, version, endVersion);
        ImmutableList<Delta<String>> data = history.getData();
        obj.add(Params.DELTAS, serializeDeltas(version, data));
        if (data.isEmpty()) {
            return true;
        }
        if (history.hasMore()) {
            obj.addProperty(Params.HAS_MORE, history.hasMore());
        }
        return false;
    }
}