Java URL

URLUniform Resource Locator FTP

Java URL URL 

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

protocol() HTTPHTTPSFTP Fileport path

HTTP URL :

http://www.runoob.com/index.html?language=cn#j2se

URL

  • (protocol)http
  • (host:port)www.runoob.com
  • (port): 80 URL HTTP 80
  • (path)/index.html
  • (query)language=cn
  • (fragment)j2se id j2se HTML

URL

java.netURLURLURL

java.net.URLURLjava.net.URL

1public URL(String protocol, String host, int port, String file) throws MalformedURLException.
()URL
2public URL(String protocol, String host, String file) throws MalformedURLException
URL
3public URL(String url) throws MalformedURLException
URLURL
4public URL(URL context, String url) throws MalformedURLException
URL

URLURL

1public String getPath()
URL
2public String getQuery()
URL
3public String getAuthority()
URL
4public int getPort()
URL
5public int getDefaultPort()
6public String getProtocol()
URL
7public String getHost()
URL
8public String getFile()
URL
9public String getRef()
URL ""
10public URLConnection openConnection() throws IOException
URL

java.netURLURL

URLDemo.java

import java.net.*; import java.io.*; public class URLDemo { public static void main(String [] args) { try { URL url = new URL("http://www.runoob.com/index.html?language=cn#j2se"); System.out.println("URL " + url.toString()); System.out.println("" + url.getProtocol()); System.out.println("" + url.getAuthority()); System.out.println("" + url.getFile()); System.out.println("" + url.getHost()); System.out.println("" + url.getPath()); System.out.println("" + url.getPort()); System.out.println("" + url.getDefaultPort()); System.out.println("" + url.getQuery()); System.out.println("" + url.getRef()); }catch(IOException e) { e.printStackTrace(); } } }

:

URL http://www.runoob.com/index.html?language=cn#j2se
http
www.runoob.com
/index.html?language=cn
www.runoob.com
/index.html
-1
80
language=cn
j2se

URLConnections

openConnection() java.net.URLConnection

  • HTTPURL, openConnection() HttpURLConnection

  • URL JAR , openConnection() JarURLConnection

  • ...

URLConnection

1Object getContent()
URL
2Object getContent(Class[] classes)
URL
3String getContentEncoding()
content-encoding
4int getContentLength()
content-length
5String getContentType()
content-type
6int getLastModified()
last-modified
7long getExpiration()
expires
8long getIfModifiedSince()
ifModifiedSince
9public void setDoInput(boolean input)
URL / URL DoInput true false true
10public void setDoOutput(boolean output)
URL / URL DoOutput true false false
11public InputStream getInputStream() throws IOException
URL
12public OutputStream getOutputStream() throws IOException
URL,
13public URL getURL()
URLConnection URL

URLHTTP openConnection HttpURLConnection

URLConnDemo.java

import java.net.*; import java.io.*; public class URLConnDemo { public static void main(String [] args) { try { URL url = new URL("http://www.runoob.com"); URLConnection urlConnection = url.openConnection(); HttpURLConnection connection = null; if(urlConnection instanceof HttpURLConnection) { connection = (HttpURLConnection) urlConnection; } else { System.out.println(" URL "); 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(); } } }

$ javac URLConnDemo.java 
$ java URLConnDemo
.....(http://www.runoob.com) HTML .....