Java URL handling

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 URL (Uniform Resource Locator) Chinese called a Uniform Resource Locator, sometimes referred to as a web page address. Expressed as a resource on the Internet, such as Web or FTP address.

URL can be divided into several parts as follows:

protocol：//host:port/path?query#fragment

 

protocol (protocol) can be HTTP, HTTPS, FTP and File, port is the port number, path is the file path and file name.

 

URL parsing:

• Protocol (protocol): http
• Host (host: port): www.baidu.com
• Port number (port): 80, did not specify the instance above URL port, because HTTP protocol default port number is 80.
• File path (path): / index.html
• Parameter request (query): language = cn
• Positioning location (fragment): j2se, to pages as the id attribute of the HTML element j2se position.

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URL class method

java.net package defines the URL class, processing contents related to the URL. To create and use the URL class, described separately below.

java.net.URL provides a wealth of URL built, and resources can be obtained by java.net.URL.

URL in a class contains many methods for accessing the various portions of the URL, specific methods are described below:

Examples

package pkg2020华南虎;

import java.net.*;
import java.io.*;

/**
 *
 * @author yl
 */
public class URLDemo {

    public static void main(String[] args) {
        try {
            URL url = new URL("https://i-beta.cnblogs.com/posts/edit;postId=12299874");
            System.out.println("URL为：" + url.toString());
            System.out.println("协议为：" + url.getProtocol());
            System.out.println("验证信息：" + url.getAuthority());
            System.out.println("文件名及请求参数：" + url.getFile());
            System.out.println("主机名：" + url.getHost());
            System.out.println("路径：" + url.getPath());
            System.out.println("端口：" + url.getPort());
            System.out.println("默认端口：" + url.getDefaultPort());
            System.out.println("请求参数：" + url.getQuery());
            System.out.println("定位位置：" + url.getRef());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

 

结果：

run:
URL为：https://i-beta.cnblogs.com/posts/edit;postId=12299874
协议为：https
验证信息：i-beta.cnblogs.com
文件名及请求参数：/posts/edit;postId=12299874
主机名：i-beta.cnblogs.com
路径：/posts/edit;postId=12299874
端口：-1
默认端口：443
请求参数：null
定位位置：null
成功构建 (总时间: 0 秒)

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URLConnections类方法　　

openConnection()返回一个java.net.URLConnection.

例如：

• 如果你连接HTTP协议的URL，openConnection()方法返回HttpURLConnection对象。
• 如果你连接的URL为一个JAR文件，openConnection()方法将返回JarURLConnection对象。

实例：

package pkg2020华南虎;

import java.net.*;
import java.io.*;

/**
 *
 * @author yl
 */
public class URLConnDemo {

    public static void main(String[] args) {
        try {
            URL url = new URL("http://www.baidu.com");
            URLConnection urlConnection = url.openConnection();
            HttpURLConnection connection = null;
            if (urlConnection instanceof HttpURLConnection) {
                connection = (HttpURLConnection) urlConnection;
            } else {
                System.out.println("请输入URL地址");
                return;
            }
            BufferedReader in = new BufferedReader(
                    new InputStreamReader(connection.getInputStream())
            );
            String urlString = "";
            String current;
            while ((current = in.readLine()) != null) {
                urlString += current;
            }
            System.out.println(urlString);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

会输出百度首页。

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