/*
* Copyright (C) 2014 hu
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
package cn.edu.hfut.dmic.webcollector.generator.filter;
import cn.edu.hfut.dmic.webcollector.generator.Generator;
import cn.edu.hfut.dmic.webcollector.model.CrawlDatum;
import java.util.HashSet;
/**
* 唯一性过滤器
* @author hu
*/
public class UniqueFilter extends Filter{
/**
* 构建一个唯一性过滤器
* @param generator 嵌套的过滤器
*/
public UniqueFilter(Generator generator) {
super(generator);
}
private HashSet<String> hashset=new HashSet<String>();
/**
* 添加一个URL，以后该过滤器遇到相同URL会过滤
* @param url
*/
public void addUrl(String url){
hashset.add(url);
}
/**
* 获取下一个URL不重复的任务
* @return 下一个URL不重复的爬取任务，如果没有符合规则的任务，返回null
*/
@Override
public CrawlDatum next() {
while(true){
CrawlDatum crawldatum=generator.next();
if(crawldatum==null){
return null;
}
String url=crawldatum.getUrl();
if(hashset.contains(url)){
continue;
}
else{
addUrl(url);
return crawldatum;
}
}
}
}