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URL is the abbreviation of Uniform Resource Locator (Uniform Resource Locator), which represents the address of a resource on the Internet. Through URLs, users can access various network resources, such as common WWW and FTP sites. A browser can parse a given URL to find the corresponding file or other resource on the network.
URL class
The java.net package contains a class URL specially used to process URLs, and you can get the URL related Information, such as the protocol name and host name of the URL.
URLConnection class
After completing the definition of URL, you can then obtain the communication connection of the URL. In the java.net package, a special URLConnection class is defined to represent the communication connection established with the URL. The object of the URLConnection class is obtained using the openConnection() method of the URL class.
Example:
Use the URL and URLConnection classes to obtain the link to the Baidu homepage and output its page information to the console. The main steps are as follows.
(1) Create a class, write the main() method, create a URL object in this method, and then pass in the parameter "http://www.baidu.com/" and output the URL The relevant information, the code is as follows.
package ch16;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
public class URLDemo
{
public static void main(String[] args)
{
try
{
URL url=new URL("http://www.baidu.com/");
System.out.println("协议：" + url.getProtocol());//获取该 URL 的协议名。
System.out.println("主机：" + url.getHost());//获取该 URL 的主机名。
System.out.println("端口：" + url.getPort());//获取该 URL 的端口号，如果没有设置端口，返回 -1。
InputStream in;
}
catch(IOException e)
{
//TODO 自动生成的 catch 块
e.printStackTrace();
}
}
}
(2) Continue to add code in the try module of the main() method, obtain the URLConnection object, read the page source code through the input stream and output the information to the console, code As follows.
URLConnection uc=url.openConnection();
in=uc.getInputStream();//返回从此打开的链接读取的输入流。
byte[] b=new byte[1024];
int len;
while((len=in.read(b))!=-1)
{
System.out.println(new String(b,0,len));
}
in.close();
(3) Run the program and the execution results are as follows.
协议：http 主机：www.baidu.com 端口：-1 <!DOCTYPE html> <!--STATUS OK--><html> <head><meta http-equiv=content-type content=text/html;charset=utf-8> <meta http-equiv=X-UA-Compatible content=IE=Edge><meta content=always name=referrer> <link rel=stylesheet type=text/css href=http://s1.bdstatic.com/r/www/cache/......<img src=//www.baidu.com/img/gs.gif> </p> </div> </div> </div> </body> </html>
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