Why does Java's URL class not recognize certain protocols?
Solution 1
Issue
Java throws a MalformedURLException
because it couldn't find a URLStreamHandler
for that protocol. Check the javadocs of the constructors for the details.
Summary
Since the URL
class has an openConnection
method, the URL class checks to make sure that Java knows how to open a connection of the correct protocol. Without a URLStreamHandler
for that protocol, Java refuses to create a URL
to save you from failure when you try to call openConnection
.
Solution
You should probably be using the URI
class if you don't plan on opening a connection of those protocols in Java.
Solution 2
Sounds like there's no registered handler for the protocol "telnet" in your application. Since the URL class can be used to open a InputStream to URL it needs to have a registered handler for the protocol to do this work if you're to be allowed to create an object using it.
For details on how to add handlers see: http://docs.oracle.com/javase/7/docs/api/java/net/URLStreamHandlerFactory.html
Solution 3
The simple answer is that it only does recognize certain protocols, and the remainder of the infinity of protocols is not recognized.
Solution 4
You're getting that error because java doesn't have a standard protocol handler for telnet.
Comments
-
trinity almost 2 years
URL u=new URL("telnet://route-server.exodus.net");
This line is generating :
java.net.MalformedURLException: unknown protocol: telnet
And I encounter similar problems with other URLs that begin with "news://"
These are URLs extracted from ODP, so I don't understand why such exceptions arise..