URLFetcher.java

/*
 * polycasso - Cubism Artwork generator
 * Copyright 2009-2017 MeBigFatGuy.com
 * Copyright 2009-2017 Dave Brosius
 * Inspired by work by Roger Alsing
 *
 * 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.mebigfatguy.polycasso;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.InetSocketAddress;
import java.net.MalformedURLException;
import java.net.Proxy;
import java.net.Proxy.Type;
import java.net.URL;
import java.util.Base64;

import org.apache.commons.io.IOUtils;

/**
 * manages downloading data from a url
 */
public class URLFetcher {

    /**
     * private to avoid construction of this static access only class
     */
    private URLFetcher() {
    }

    /**
     * retrieve arbitrary data found at a specific url - either http or file urls for http requests, sets the user-agent to mozilla to avoid sites being cranky
     * about a java sniffer
     *
     * @param url
     *            the url to retrieve
     * @param proxyHost
     *            the host to use for the proxy
     * @param proxyPort
     *            the port to use for the proxy
     * @return a byte array of the content
     *
     * @throws IOException
     *             the site fails to respond
     */
    public static byte[] fetchURLData(String url, String proxyHost, int proxyPort) throws IOException {
        HttpURLConnection con = null;
        InputStream is = null;

        try {
            URL u = new URL(url);
            if (url.startsWith("file://")) {
                is = new BufferedInputStream(u.openStream());
            } else {
                Proxy proxy;
                if (proxyHost != null) {
                    proxy = new Proxy(Type.HTTP, new InetSocketAddress(proxyHost, proxyPort));
                } else {
                    proxy = Proxy.NO_PROXY;
                }
                con = (HttpURLConnection) u.openConnection(proxy);
                con.addRequestProperty("User-Agent",
                        "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.6 (KHTML, like Gecko) Chrome/20.0.1092.0 Safari/536.6");
                con.addRequestProperty("Accept-Charset", "UTF-8");
                con.addRequestProperty("Accept-Language", "en-US,en");
                con.addRequestProperty("Accept", "text/html,image/*");
                con.setDoInput(true);
                con.setDoOutput(false);
                con.connect();

                is = new BufferedInputStream(con.getInputStream());
            }

            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            IOUtils.copy(is, baos);
            return baos.toByteArray();
        } catch (MalformedURLException e) {
            if (url.startsWith("data:")) {
                int commaPos = url.indexOf(",");
                if (commaPos < 0) {
                    throw new IOException("Poorly formatted data url");
                }
                String prefix = url.substring("data:".length(), commaPos);
                String[] attributes = prefix.trim().split(";");
                if (attributes.length < 0) {
                    throw new IOException("Data url doesn't specify mime type");
                }

                String data = url.substring(commaPos + 1);
                switch (attributes[0]) {
                    case "image/jpeg":
                    case "image/png":
                    case "image/gif":
                        return Base64.getDecoder().decode(data);

                    default:
                        throw new IOException("Unsupported data url mimetype: " + attributes[0]);
                }
            } else {
                throw e;
            }
        } finally {
            IOUtils.closeQuietly(is);
            if (con != null) {
                con.disconnect();
            }
        }
    }
}