python爬虫初步-与java爬虫的比较

相比较java来说,python的http库类更佳丰富,用java需要几十行代码才能完成的事情,python往往只需要十几行,例如打开并且存储一个网页

java代码:

import java.io.BufferedReader;

import java.io.FileOutputStream;

import java.io.FileWriter;

import java.io.IOException;

import java.io.InputStreamReader;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;

public class HeaderTest {
public static void main(String[] args) {
new HeaderTest().downloadHtml("http://www.bilibili.com");
}
public void downloadHtml(String link){
BufferedReader reader = null;
FileWriter writer = null;
try {
URL url = new URL(link);
URLConnection con = url.openConnection();
reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
writer = new FileWriter("f://test1.txt");
String buff = null;
StringBuilder sb = new StringBuilder();
while((buff = reader.readLine()) != null){
writer.write(buff);
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
reader.close();
writer.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

}

python代码:

import urllib.request

def down
4000
loadHtml(link):
try:
data = urllib.request.urlopen(link).read()
text = data.decode('utf-8','ignore')
file = open('f:\\test2.txt','w')
file.write(text)
file.close()
except urllib.request.URLError as e:
print(e.reason)
downloadHtml("http://www.bilibili.com")

然而这种爬取网站的方式是不安全的,1是网站会根据访问者的类型来屏蔽访问.2是在爬取的时候访问网站会非常频繁,网站会封掉我们的IP

我们需要欺骗网站,在java中实现这一点比较常用的是使用HttpClient的jar包来实现

java代码如下

import java.io.BufferedInputStream;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import org.apache.http.HttpEntity;

import org.apache.http.HttpHost;

import org.apache.http.HttpRequest;

import org.apache.http.HttpResponse;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.config.RequestConfig;

import org.apache.http.client.methods.CloseableHttpResponse;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.CloseableHttpClient;

import org.apache.http.impl.client.HttpClients;

import org.apache.http.impl.execchain.MainClientExec;

public class HttpclientTest {
public static void main(String[] args){
System.out.println(new HttpclientTest().gethtml("http://www.bilibili.com"));
}
public String gethtml(String url){
String html = null;
//建立HttpClient类,这是HttpClient的jar包中的一个类
CloseableHttpClient httpclient = HttpClients.createDefault();
//读取html的流
BufferedReader reader = null;
//设置请求信息
HttpGet getmethod = new HttpGet(url);
//响应
HttpResponse response = null;
//设置代理IP
HttpHost proxy = new HttpHost("124.88.67.81",80);
//设置超时时间
RequestConfig config = RequestConfig.custom().setProxy(proxy).setConnectTimeout(5000).setConnectionRequestTimeout(5000).setSocketTimeout(5000).build();
//添加请求头
getmethod.addHeader("User-Agent","Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36");
getmethod.setConfig(config);
try {
//获得响应
response = httpclient.execute(getmethod);
//响应体
HttpEntity entity = response.getEntity();
//建立一个读取流
reader = new BufferedReader(new InputStreamReader(entity.getContent()));
//读取html
String buff = null;
StringBuilder sb = new StringBuilder();
while((buff = reader.readLine()) != null){
sb.append(buff);
}
html = sb.toString();
System.out.println();
return html;
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.println("读取异常");
return null;
}finally{
try {
httpclient.close();
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.println("关闭资源失败");
}
}
}

}

在这段代码中我们设置了代理ip,请求头中的user-agent被我们设置成谷歌浏览器的内核,这样网站会认为我们是浏览器

python代码:

import urllib.request

def downloadHtml(link):
try:
proxy = {"http":"123.179.128.170:8080"}
proxy_support = urllib.request.ProxyHandler(proxy)
headers = ( "User-Agent","Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36")
opener = urllib.request.build_opener(proxy_support)
opener.addheaders = [headers]

opener = urllib.request.build_opener(proxy_support)

data = opener.open(link).read() text = data.decode('utf-8','ignore') print(text) except urllib.request.URLError as e: print(e.reason)def dowmloadHtml2(link): req = urllib.request.Request(link) req.add_header("User-Agent","Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36") data = urllib.request.urlopen(req,timeout=1).read() text = data.decode("utf-8","ignore") print(text)downloadHtml("http://blog.csdn.net/weiwei_pig/article/details/51178226")