urlconnectionsample.java

精通Java网络编程代码全部

//URLConnection.java
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Date;

public class URLConnectionSample {
	public static void main(String[] args) {
		//只接受一个命令行参数，这个参数作为URL使用
		if (1 != args.length) {
			System.err.println("Usage: java URLConnectionSample url");
			return;
		}
		try {
			//读取命令行参数，将第一个参数解释为URL
			URL url = new URL(args[0]);
			// 通过URL对象构造URLConnection对象
			URLConnection con = url.openConnection();
			//连接到URL
			con.connect();
			//输出相关的信息
			System.out.println(" Content Type: " + con.getContentType());
			System.out.println(" Content Encoding: " + con.getContentEncoding());
			System.out.println(" Content Length: " + con.getContentLength());
			System.out.println(" Date: " + new Date(con.getDate()));
			System.out.println(" Last Modified: " + new Date(con.getLastModified()));
			System.out.println(" Expiration: " + new Date(con.getExpiration()));
			//如果URL对象的协议被设置为HTTP协议，
			//那么返回的URLConnection对象实际上是一个HttpURLConnection对象
			//通过使用HTTPURLConnection对象，可以获得一些与HTTP协议相关的
			//信息，如状态码
			if (con instanceof HttpURLConnection) {
				HttpURLConnection h = (HttpURLConnection) con;
				System.out.println(" Request Method: " + h.getRequestMethod());
				System.out.println(" Response Message: " + h.getResponseMessage());
				//返回服务器发回的状态码，如果状态码不是2xx，那么肯定发生了错误
				System.out.println(" Response Code: " + h.getResponseCode());
			}
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}