de.comlineag.snc.webcrawler.robotstxt.RobotstxtServer.java Source code

Introduction

Here is the source code for de.comlineag.snc.webcrawler.robotstxt.RobotstxtServer.java

Source

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 de.comlineag.snc.webcrawler.robotstxt;

import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.http.HttpStatus;

import de.comlineag.snc.webcrawler.crawler.Page;
import de.comlineag.snc.webcrawler.fetcher.PageFetchResult;
import de.comlineag.snc.webcrawler.fetcher.PageFetcher;
import de.comlineag.snc.webcrawler.url.WebURL;
import de.comlineag.snc.webcrawler.util.WebCrawlerUtil;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Yasser Ganjisaffar <lastname at gmail dot com>
 */
public class RobotstxtServer {

    private static final Logger logger = LoggerFactory.getLogger(RobotstxtServer.class);

    protected RobotstxtConfig config;

    protected final Map<String, HostDirectives> host2directivesCache = new HashMap<>();

    protected PageFetcher pageFetcher;

    public RobotstxtServer(RobotstxtConfig config, PageFetcher pageFetcher) {
        this.config = config;
        this.pageFetcher = pageFetcher;
    }

    private static String getHost(URL url) {
        return url.getHost().toLowerCase();
    }

    public boolean allows(WebURL webURL) {
        if (!config.isEnabled()) {
            return true;
        }
        try {
            URL url = new URL(webURL.getURL());
            String host = getHost(url);
            String path = url.getPath();

            HostDirectives directives = host2directivesCache.get(host);

            if (directives != null && directives.needsRefetch()) {
                synchronized (host2directivesCache) {
                    host2directivesCache.remove(host);
                    directives = null;
                }
            }

            if (directives == null) {
                directives = fetchDirectives(url);
            }
            return directives.allows(path);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        return true;
    }

    private HostDirectives fetchDirectives(URL url) {
        WebURL robotsTxtUrl = new WebURL();
        String host = getHost(url);
        String port = (url.getPort() == url.getDefaultPort() || url.getPort() == -1) ? "" : ":" + url.getPort();
        robotsTxtUrl.setURL("http://" + host + port + "/robots.txt");
        HostDirectives directives = null;
        PageFetchResult fetchResult = null;
        try {
            fetchResult = pageFetcher.fetchHeader(robotsTxtUrl);
            if (fetchResult.getStatusCode() == HttpStatus.SC_OK) {
                Page page = new Page(robotsTxtUrl);
                fetchResult.fetchContent(page);
                if (WebCrawlerUtil.hasPlainTextContent(page.getContentType())) {
                    try {
                        String content;
                        if (page.getContentCharset() == null) {
                            content = new String(page.getContentData());
                        } else {
                            content = new String(page.getContentData(), page.getContentCharset());
                        }
                        directives = RobotstxtParser.parse(content, config.getUserAgentName());
                    } catch (Exception e) {
                        logger.error("Error occurred while fetching (robots) url: " + robotsTxtUrl.getURL(), e);
                    }
                }
            }
        } finally {
            if (fetchResult != null) {
                fetchResult.discardContentIfNotConsumed();
            }
        }
        if (directives == null) {
            // We still need to have this object to keep track of the time we
            // fetched it
            directives = new HostDirectives();
        }
        synchronized (host2directivesCache) {
            if (host2directivesCache.size() == config.getCacheSize()) {
                String minHost = null;
                long minAccessTime = Long.MAX_VALUE;
                for (Entry<String, HostDirectives> entry : host2directivesCache.entrySet()) {
                    if (entry.getValue().getLastAccessTime() < minAccessTime) {
                        minAccessTime = entry.getValue().getLastAccessTime();
                        minHost = entry.getKey();
                    }
                }
                host2directivesCache.remove(minHost);
            }
            host2directivesCache.put(host, directives);
        }
        return directives;
    }
}