URL : Java Glossary

URL

Uniform Resource Locator. The old name for URI. RFC 4248 describes URL formats. RFC 3986 describes URI formats. java.net.URL has been replaced by java.net.URI. Strictly speaking, every URL is a URI, but not every URI is a URL. URI’s are an extension and refinement of the URL. Yet, as classes, neither is a subclass of the other and they have no common base other than Object. java.net. URI is Java’s second attempt at doin a URL class an they started from scratch.

URLs never automatically armour their parameters, where URIs sometimes do.

If a bug report I got is correct, under some conditions JDK 1.6 URL.openConnection returns null without throwing an IOException.

The term URL can also be an as a verb, as in “Please URL me that picture of the Windows Firewall”, meaning “Please email me the URL of that photograph”, in other words email the text: http://mindprod.com/image/jgloss/msfirewall.jpg.

Non-ASCII URLs

What if you wanted to embed the following URL in your HTML?

What do you do about that pesky non-ASCII ç character? HTML 4.01 says URLs should only contain ASCII chars, but if non-ASCII chars appear they should be treated as UTF-8. In theory you should be able to encode it with ç, ç or ç, but in practice, you can’t count on this working. You must use the URL-Encoded %hh escaping mechanism of the equivalent UTF-8 chars like this:

+ is converted to %2B and space is converted to +.

URLs always use UTF-8 encoding, no matter what the encoding of the enclosing document.

Learning More

Sun’s Javadoc on URL class : available:

on the web at java.sun.com
in the current JDK 1.6.0_17 or in the old JDK 1.5.0_22 on your local Windows J: drive.

Sun’s Javadoc on URI class : available:

on the web at java.sun.com
in the current JDK 1.6.0_17 or in the old JDK 1.5.0_22 on your local Windows J: drive.

Sun’s tutorial on URL Introductory

firewall
getResource to create URLs
IDN
makeashorterlink
protocol handler
SnipURL
TinyURL
URI
url-encoded
URLConnection
URN

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