Java爬虫实战（一）：抓取一个网站上的全部链接
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package
action;
import
java.io.BufferedReader;
import
java.io.IOException;
import
java.io.InputStream;
import
java.io.InputStreamReader;
import
java.net.HttpURLConnection;
import
java.net.MalformedURLException;
import
java.net.URL;
import
java.util.LinkedHashMap;
import
java.util.Map;
import
java.util.regex.Matcher;
import
java.util.regex.Pattern;
public
class
WebCrawlerDemo {
public
static
void
main(String[] args) {
WebCrawlerDemo webCrawlerDemo =
new
WebCrawlerDemo();
webCrawlerDemo.myPrint(
"http://www.zifangsky.cn"
);
}
public
void
myPrint(String baseUrl) {
Map
new
LinkedHashMap
// 存储链接-是否被遍历
// 键值对
String oldLinkHost =
""
;
//host
Pattern p = Pattern.compile(
"(https?://)?[^/\\s]*"
); //比如：http://www.zifangsky.cn
Matcher m = p.matcher(baseUrl);
if
(m.find()) {
oldLinkHost = m.group();
}
oldMap.put(baseUrl,
false
);
oldMap = crawlLinks(oldLinkHost, oldMap);
for
(Map.Entry
System.out.println(
"链接："
+ mapping.getKey());
}
}
/**
* 抓取一个网站所有可以抓取的网页链接，在思路上使用了广度优先算法
* 对未遍历过的新链接不断发起GET请求，一直到遍历完整个集合都没能发现新的链接
* 则表示不能发现新的链接了，任务结束
*
* @param oldLinkHost 域名，如：http://www.zifangsky.cn
* @param oldMap 待遍历的链接集合
*
* @return 返回所有抓取到的链接集合
* */
private
Map
Map
Map
new
LinkedHashMap
String oldLink =
""
;
for
(Map.Entry
System.out.println(
"link:"
+ mapping.getKey() +
"--------check:"
+ mapping.getValue());
// 如果没有被遍历过
if
(!mapping.getValue()) {
oldLink = mapping.getKey();
// 发起GET请求
try
{
URL url =
new
URL(oldLink);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setRequestMethod(
"GET"
);
connection.setConnectTimeout(
2000
);
connection.setReadTimeout(
2000
);
if
(connection.getResponseCode() ==
200
) {
InputStream inputStream = connection.getInputStream();
BufferedReader reader =
new
BufferedReader(
new
InputStreamReader(inputStream,
"UTF-8"
));
String line =
""
;
Pattern pattern = Pattern
.compile(
"
);
Matcher matcher =
null
;
while
((line = reader.readLine()) !=
null
) {
matcher = pattern.matcher(line);
if
(matcher.find()) {
String newLink = matcher.group(
1
).trim();
// 链接
// String title = matcher.group(3).trim(); //标题
// 判断获取到的链接是否以http开头
if
(!newLink.startsWith(
"http"
)) {
if
(newLink.startsWith(
"/"
))
newLink = oldLinkHost + newLink;
else
newLink = oldLinkHost +
"/"
+ newLink;
}
//去除链接末尾的 /
if
(newLink.endsWith(
"/"
))
newLink = newLink.substring(
0
, newLink.length() -
1
);
//去重，并且丢弃其他网站的链接
if
(!oldMap.containsKey(newLink)
&& !newMap.containsKey(newLink)
&& newLink.startsWith(oldLinkHost)) {
// System.out.println("temp2: " + newLink);
newMap.put(newLink,
false
);
}
}
}
}
}
catch
(MalformedURLException e) {
e.printStackTrace();
}
catch
(IOException e) {
e.printStackTrace();
}
try
{
Thread.sleep(
1000
);
}
catch
(InterruptedException e) {
e.printStackTrace();
}
oldMap.replace(oldLink,
false
,
true
);
}
}
//有新链接，继续遍历
if
(!newMap.isEmpty()) {
oldMap.putAll(newMap);
oldMap.putAll(crawlLinks(oldLinkHost, oldMap));
//由于Map的特性，不会导致出现重复的键值对
}
return
oldMap;
}
}
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