Java网络编程之URI、URL研究（下） 02

列表4是URLDemo1的源代码。该程序从命令行参数建立了一个URL对象，调用URL组件提取方法来检索该URL的组件，调用URL的openStream()方法打开与资源的连接并返回一个用于从资源读取字节数据的InputStream引用，读取/打印这些字节，关闭输入流。

　　列表4: URLDemo1.java

// URLDemo1.java
import java.io.*;
import java.net.*;

class URLDemo1
{
public static void main (String [] args) throws IOException
{
if (args.length != 1)
{
System.err.println ("usage: java URLDemo1 url");
return;
}

URL url = new URL (args [0]);

System.out.println ("Authority = "+ url.getAuthority ());
System.out.println ("Default port = " +url.getDefaultPort ());
System.out.println ("File = " +url.getFile ());
System.out.println ("Host = " +url.getHost ());
System.out.println ("Path = " +url.getPath ());
System.out.println ("Port = " +url.getPort ());
System.out.println ("Protocol = " +url.getProtocol ());
System.out.println ("Query = " +url.getQuery ());
System.out.println ("Ref = " +url.getRef ());
System.out.println ("User Info = " +url.getUserInfo ());

System.out.print ('\n');

InputStream is = url.openStream ();

int ch;
while ((ch = is.read ()) != -1)
System.out.print ((char) ch);

is.close ();
}
}

　　在命令行输入java URLDemo1 http://www.javajeff.com/articles/articles/html后，上面的代码的输出如下：

Authority = http://www.javajeff.com
Default port = 80
File = /articles/articles.html
Host = http://www.javajeff.com
Path = /articles/articles.html
Port = -1
Protocol = http
Query = null
Ref = null
User Info = null

＜html＞
＜head＞
＜title＞
Java Jeff - Articles
＜/title＞

＜meta http-equiv=Content-Type content="text/html;
charset=ISO-8859-1"＞
＜meta name=author content="Jeff Friesen"＞
＜meta name=keywords content="java, virtual machine"＞

＜script language=JavaScript＞
if (navigator.appName == "Netscape")
document.write ("＜br＞");
＜/script＞
＜/head＞

＜body bgcolor=#000000＞
＜center＞
＜table border=1 cellpadding=5 cellspacing=0＞
＜tr＞
＜td＞
＜table cellpadding=0 cellspacing=0＞
＜tr＞
＜td＞
＜a href=informit/informit.html＞
＜img alt=InformIT border=0 src=informit.gif＞＜/a＞
＜/td＞
＜/tr＞
＜/table＞
＜/td＞

＜td align=middle＞
＜img src=title.gif＞＜br＞

＜a href=../welcome/welcome.html＞
＜img alt="Welcome to Java Jeff!" border=0 src=jupiter.jpg＞
＜/a＞＜br＞

＜img src=../common/clear_dot.gif vspace=5＞＜br＞

＜a href=../ads/ads.html＞
＜img alt="Welcome to Java Jeff!" border=0
src=jupiter.jpg＞
＜/td＞

＜td＞
＜table cellpadding=0 cellspacing=0＞
＜tr＞
＜td＞
＜a href=javaworld/javaworld.html＞
＜img alt=JavaWorld border=0 src=javaworld.gif＞＜/a＞
＜/td＞
＜/tr＞
＜/table＞
＜/td＞
＜/tr＞
＜/table＞
＜/center＞

＜br＞
＜font color=#ffffff＞
＜center＞
Best viewed at a resolution of 1024x768 or higher.＜br＞

＜img src=../common/clear_dot.gif vspace=5＞＜br＞

＜i＞
Copyright © 2001-2002, Jeff Friesen. All rights
reserved.
＜/i＞

＜p＞
＜a href=../index.html＞
＜img alt=Back border=0 src=../common/back.gif＞＜/a＞
＜/center＞
＜/font＞
＜/body＞
＜/html＞

　　在上面的信息中，输出标识符80是默认端口，HTTP是协议。上面给出的是输出的HTML页面的源代码。