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java.lang.Object | +--java.net.URL
Class URL
represents a Uniform Resource
Locator, a pointer to a "resource" on the World
Wide Web. A resource can be something as simple as a file or a
directory, or it can be a reference to a more complicated object,
such as a query to a database or to a search engine. More
information on the types of URLs and their formats can be found at:
http://www.ncsa.uiuc.edu/demoweb/url-primer.html
In general, a URL can be broken into several parts. The previous
example of a URL indicates that the protocol to use is
http
(HyperText Transfer Protocol) and that the
information resides on a host machine named
www.ncsa.uiuc.edu
. The information on that host
machine is named /demoweb/url-primer.html
. The exact
meaning of this name on the host machine is both protocol
dependent and host dependent. The information normally resides in
a file, but it could be generated on the fly. This component of
the URL is called the path component.
A URL can optionally specify a "port", which is the
port number to which the TCP connection is made on the remote host
machine. If the port is not specified, the default port for
the protocol is used instead. For example, the default port for
http
is 80
. An alternative port could be
specified as:
http://www.ncsa.uiuc.edu:8080/demoweb/url-primer.html
A URL may have appended to it a "fragment", also known as a "ref" or a "reference". The fragment is indicated by the sharp sign character "#" followed by more characters. For example,
http://java.sun.com/index.html#chapter1
This fragment is not technically part of the URL. Rather, it
indicates that after the specified resource is retrieved, the
application is specifically interested in that part of the
document that has the tag chapter1
attached to it. The
meaning of a tag is resource specific.
An application can also specify a "relative URL", which contains only enough information to reach the resource relative to another URL. Relative URLs are frequently used within HTML pages. For example, if the contents of the URL:
contained within it the relative URL:http://java.sun.com/index.html
it would be a shorthand for:FAQ.html
http://java.sun.com/FAQ.html
The relative URL need not specify all the components of a URL. If the protocol, host name, or port number is missing, the value is inherited from the fully specified URL. The file component must be specified. The optional fragment is not inherited.
CDLC AWT Support Building Block: This class is subsetted to only represent the URL as a location specification. All links to the J2SE IO model for controlling URL connections has been removed since J2ME and CLDC use a very different IO model. In the CLDC context, this class is used to verify, contstruct, and decontruct URL strings. Classes removed include: - URL(java.lang.String protocol, java.lang.String host, int port, java.lang.String file, java.net.URLStreamHandler handler) - URL(URL context, java.lang.String spec, java.net.URLStreamHandler handler) - getContent() - getContent(java.lang.Class[] classes) - openConnection() - openStream() - setURLStreamHandlerFactory()
Constructor Summary | |
URL(java.lang.String spec)
Creates a URL object from the String
representation. |
|
URL(java.lang.String protocol,
java.lang.String host,
int port,
java.lang.String file)
Creates a URL object from the specified
protocol , host , port
number, and file . |
|
URL(java.lang.String protocol,
java.lang.String host,
java.lang.String file)
Creates a URL from the specified protocol
name, host name, and file name. |
|
URL(URL context,
java.lang.String spec)
Creates a URL by parsing the given spec within a specified context. |
Method Summary | |
boolean |
equals(java.lang.Object obj)
Compares two URLs. |
java.lang.String |
getAuthority()
Returns the authority part of this URL . |
java.lang.String |
getFile()
Returns the file name of this URL . |
java.lang.String |
getHost()
Returns the host name of this URL , if applicable. |
java.lang.String |
getPath()
Returns the path part of this URL . |
int |
getPort()
Returns the port number of this URL . |
java.lang.String |
getProtocol()
Returns the protocol name of this URL . |
java.lang.String |
getQuery()
Returns the query part of this URL . |
java.lang.String |
getRef()
Returns the anchor (also known as the "reference") of this URL . |
java.lang.String |
getUserInfo()
Returns the userInfo part of this URL . |
int |
hashCode()
Creates an integer suitable for hash table indexing. |
boolean |
sameFile(URL other)
Compares two URLs, excluding the "ref" fields. |
protected void |
set(java.lang.String protocol,
java.lang.String host,
int port,
java.lang.String file,
java.lang.String ref)
Sets the fields of the URL. |
protected void |
set(java.lang.String protocol,
java.lang.String host,
int port,
java.lang.String authority,
java.lang.String userInfo,
java.lang.String path,
java.lang.String query,
java.lang.String ref)
Sets the specified 8 fields of the URL. |
java.lang.String |
toExternalForm()
Constructs a string representation of this URL . |
java.lang.String |
toString()
Constructs a string representation of this URL . |
Methods inherited from class java.lang.Object |
getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
public URL(java.lang.String protocol, java.lang.String host, int port, java.lang.String file) throws MalformedURLException
URL
object from the specified
protocol
, host
, port
number, and file
. Specifying a port
number of -1
indicates that the URL should use
the default port for the protocol.
protocol
- the name of the protocol to use.host
- the name of the host.port
- the port number on the host.file
- the file on the hostMalformedURLException
- if an unknown protocol is specified.public URL(java.lang.String protocol, java.lang.String host, java.lang.String file) throws MalformedURLException
protocol
name, host
name, and file
name. The
default port for the specified protocol is used.
This method is equivalent to calling the four-argument
constructor with the arguments being protocol
,
host
, -1
, and file
.
protocol
- the name of the protocol to use.host
- the name of the host.file
- the file on the host.MalformedURLException
- if an unknown protocol is specified.URL(java.lang.String, java.lang.String, int, java.lang.String)
public URL(java.lang.String spec) throws MalformedURLException
URL
object from the String
representation.
This constructor is equivalent to a call to the two-argument
constructor with a null
first argument.
spec
- the String
to parse as a URL.MalformedURLException
- If the string specifies an
unknown protocol.URL(java.net.URL, java.lang.String)
public URL(URL context, java.lang.String spec) throws MalformedURLException
The reference is parsed into the scheme, authority, path, query and fragment parts. If the path component is empty and the scheme, authority, and query components are undefined, then the new URL is a reference to the current document. Otherwise the any fragment and query parts present in the spec are used in the new URL. If the scheme component is defined in the given spec and does not match the scheme of the context, then the new URL is created as an absolute URL based on the spec alone. Otherwise the scheme component is inherited from the context URL. If the authority component is present in the spec then the spec is treated as absolute and the spec authority and path will replace the context authority and path. If the authority component is absent in the spec then the authority of the new URL will be inherited from the context. If the spec's path component begins with a slash character "/" then the path is treated as absolute and the spec path replaces the context path. Otherwise the path is treated as a relative path and is appended to the context path. The path is canonicalized through the removal of directory changes made by occurences of ".." and ".". For a more detailed description of URL parsing, refer to RFC2396.<scheme>://<authority><path>?<query>#<fragment>
context
- the context in which to parse the specification.spec
- the String
to parse as a URL.MalformedURLException
- if no protocol is specified, or an
unknown protocol is found.URL(java.lang.String, java.lang.String, int, java.lang.String)
Method Detail |
protected void set(java.lang.String protocol, java.lang.String host, int port, java.lang.String file, java.lang.String ref)
protocol
- the name of the protocol to usehost
- the name of the hostport
- the port number on the hostfile
- the file on the hostref
- the internal reference in the URLprotected void set(java.lang.String protocol, java.lang.String host, int port, java.lang.String authority, java.lang.String userInfo, java.lang.String path, java.lang.String query, java.lang.String ref)
protocol
- the name of the protocol to usehost
- the name of the hostport
- the port number on the hostauthority
- the authority part for the urluserInfo
- the username and passwordpath
- the file on the hostref
- the internal reference in the URLquery
- the query part of this URLpublic java.lang.String getQuery()
URL
.URL
.public java.lang.String getPath()
URL
.URL
.public java.lang.String getUserInfo()
URL
.URL
.public java.lang.String getAuthority()
URL
.URL
.public int getPort()
URL
.
Returns -1 if the port is not set.public java.lang.String getProtocol()
URL
.URL
.public java.lang.String getHost()
URL
, if applicable.URL
.public java.lang.String getFile()
URL
.URL
.public java.lang.String getRef()
URL
.URL
.public boolean equals(java.lang.Object obj)
true
if and
only if the argument is not null
and is a
URL
object that represents the same
URL
as this object. Two URL objects are equal if
they have the same protocol and reference the same host, the
same port number on the host, and the same file and anchor on
the host.equals
in class java.lang.Object
obj
- the URL to compare against.true
if the objects are the same;
false
otherwise.public int hashCode()
hashCode
in class java.lang.Object
URL
.public boolean sameFile(URL other)
true
if this URL
and the
other
argument both refer to the same resource.
The two URL
s might not both contain the same anchor.other
- the URL
to compare against.true
if they reference the same remote object;
false
otherwise.public java.lang.String toString()
URL
.toString
in class java.lang.Object
URL(java.lang.String, java.lang.String, int, java.lang.String)
public java.lang.String toExternalForm()
URL
.URL(java.lang.String, java.lang.String, int, java.lang.String)
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