blobstoretest.DownloadServlet.java Source code

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Here is the source code for blobstoretest.DownloadServlet.java

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/*
 * Copyright (C) 2014 Andrs Testi.
 *
 * 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 blobstoretest;

import blobstoretest.shared.ErrorMessage;
import blobstoretest.shared.ErrorResponse;

import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreService;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.io.IOException;

import javax.inject.Inject;
import javax.inject.Singleton;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * This servlet downloads files from Blobstore.
 * 
 * @author Andrs Testi
 */
@Singleton
@SuppressWarnings("serial")
public class DownloadServlet extends HttpServlet {

    private final BlobstoreService blobstore;

    @Inject
    DownloadServlet(BlobstoreService blobstore) {
        this.blobstore = blobstore;
    }

    /**
     * Serves a file by means a blobKey.
     */
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String blobKey = req.getParameter("blobKey");
        if (blobKey == null) {

            ErrorResponse error = new ErrorResponse();
            error.setCode(HttpServletResponse.SC_BAD_REQUEST);
            ErrorMessage message = new ErrorMessage();
            message.setMessage("The Blobkey parameter is required");

            resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
            resp.setContentType("application/json");

            GsonBuilder builder = new GsonBuilder();
            Gson gson = builder.create();
            resp.getWriter().print(gson.toJson(error));

        } else {
            blobstore.serve(new BlobKey(blobKey), resp);
        }
    }
}