URL

URL

URL (String protocol, 
                String host, 
                int port, 
                String file)

Creates a URL object from the specified protocol, host, port number, and file.

host can be expressed as a host name or a literal IP address. If IPv6 literal address is used, it should be enclosed in square brackets ('[' and ']'), as specified by RFC 2732; However, the literal IPv6 address format defined in RFC 2373: IP Version 6 Addressing Architecture is also accepted.

Specifying a port number of -1 indicates that the URL should use the default port for the protocol.

If this is the first URL object being created with the specified protocol, a stream protocol handler object, an instance of class URLStreamHandler, is created for that protocol:

1. If the application has previously set up an instance of URLStreamHandlerFactory as the stream handler factory, then the createURLStreamHandler method of that instance is called with the protocol string as an argument to create the stream protocol handler.
2. If no URLStreamHandlerFactory has yet been set up, or if the factory's createURLStreamHandler method returns null, then the constructor finds the value of the system property:

            java.protocol.handler.pkgs
        

   If the value of that system property is not null, it is interpreted as a list of packages separated by a vertical slash character '|'. The constructor tries to load the class named:

            <package>.<protocol>.Handler
        

   where <package> is replaced by the name of the package and <protocol> is replaced by the name of the protocol. If this class does not exist, or if the class exists but it is not a subclass of URLStreamHandler, then the next package in the list is tried.
3. If the previous step fails to find a protocol handler, then the constructor tries to load from a system default package.

            <system default package>.<protocol>.Handler
        

   If this class does not exist, or if the class exists but it is not a subclass of URLStreamHandler, then a MalformedURLException is thrown.

Protocol handlers for the following protocols are guaranteed to exist on the search path :-

     http, https, ftp, file, and jar
 

No validation of the inputs is performed by this constructor.

URL

URL (String protocol, 
                String host, 
                String file)

Creates a URL from the specified 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. No validation of the inputs is performed by this constructor.

URL

URL (String protocol, 
                String host, 
                int port, 
                String file, 
                URLStreamHandler handler)

Creates a URL object from the specified protocol, host, port number, file, and handler. Specifying a port number of -1 indicates that the URL should use the default port for the protocol. Specifying a handler of null indicates that the URL should use a default stream handler for the protocol, as outlined for: java.net.URL#URL(java.lang.String, java.lang.String, int, java.lang.String)

If the handler is not null and there is a security manager, the security manager's checkPermission method is called with a NetPermission("specifyStreamHandler") permission. This may result in a SecurityException. No validation of the inputs is performed by this constructor.

URL

URL (String spec)

Creates a URL object from the String representation.

This constructor is equivalent to a call to the two-argument constructor with a null first argument.

URL

URL (URL context, 
                String spec)

Creates a URL by parsing the given spec within a specified context. The new URL is created from the given context URL and the spec argument as described in RFC2396 "Uniform Resource Identifiers : Generic * Syntax" :

          <scheme>://<authority><path>?<query>#<fragment>
 

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, as described in RFC2396. Also, in this case, 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.

URL

URL (URL context, 
                String spec, 
                URLStreamHandler handler)

Creates a URL by parsing the given spec with the specified handler within a specified context. If the handler is null, the parsing occurs as with the two argument constructor.

equals

boolean equals (Object obj)

Compares this URL for equality with another object.

If the given object is not a URL then this method immediately returns false.

Two URL objects are equal if they have the same protocol, reference equivalent hosts, have the same port number on the host, and the same file and fragment of the file.

Returns true if this URL equals o. URLs are equal if they have the same protocol, host, port, file, and reference.

Network I/O Warning

Some implementations of URL.equals() resolve host names over the network. This is problematic:

• The network may be slow. Many classes, including core collections like Map and Set expect that equals and hashCode will return quickly. By violating this assumption, this method posed potential performance problems.
• Equal IP addresses do not imply equal content. Virtual hosting permits unrelated sites to share an IP address. This method could report two otherwise unrelated URLs to be equal because they're hosted on the same server.
• The network may not be available. Two URLs could be equal when a network is available and unequal otherwise.
• The network may change. The IP address for a given host name varies by network and over time. This is problematic for mobile devices. Two URLs could be equal on some networks and unequal on others.

This problem is fixed in Android 4.0 (Ice Cream Sandwich). In that release, URLs are only equal if their host names are equal (ignoring case).

getAuthority

String getAuthority ()

Gets the authority part of this URL.

getContent

Object getContent ()

Gets the contents of this URL. This method is a shorthand for:

     openConnection().getContent()
 

getContent

Object getContent (Class[] classes)

Gets the contents of this URL. This method is a shorthand for:

     openConnection().getContent(Class[])
 

getDefaultPort

int getDefaultPort ()

Gets the default port number of the protocol associated with this URL. If the URL scheme or the URLStreamHandler for the URL do not define a default port number, then -1 is returned.

getFile

String getFile ()

Gets the file name of this URL. The returned file portion will be the same as getPath(), plus the concatenation of the value of getQuery(), if any. If there is no query portion, this method and getPath() will return identical results.

getHost

String getHost ()

Gets the host name of this URL, if applicable. The format of the host conforms to RFC 2732, i.e. for a literal IPv6 address, this method will return the IPv6 address enclosed in square brackets ('[' and ']').

getPath

String getPath ()

Gets the path part of this URL.

getPort

int getPort ()

Gets the port number of this URL.

getProtocol

String getProtocol ()

Gets the protocol name of this URL.

getQuery

String getQuery ()

Gets the query part of this URL.

getRef

String getRef ()

Gets the anchor (also known as the "reference") of this URL.

getUserInfo

String getUserInfo ()

Gets the userInfo part of this URL.

hashCode

int hashCode ()

Creates an integer suitable for hash table indexing.

The hash code is based upon all the URL components relevant for URL comparison. As such, this operation is a blocking operation.

openConnection

URLConnection openConnection (Proxy proxy)

Same as openConnection(), except that the connection will be made through the specified proxy; Protocol handlers that do not support proxing will ignore the proxy parameter and make a normal connection. Invoking this method preempts the system's default ProxySelector settings.

openConnection

URLConnection openConnection ()

Returns a URLConnection instance that represents a connection to the remote object referred to by the URL.

A new instance of URLConnection is created every time when invoking the URLStreamHandler.openConnection(URL) method of the protocol handler for this URL.

It should be noted that a URLConnection instance does not establish the actual network connection on creation. This will happen only when calling URLConnection.connect().

If for the URL's protocol (such as HTTP or JAR), there exists a public, specialized URLConnection subclass belonging to one of the following packages or one of their subpackages: java.lang, java.io, java.util, java.net, the connection returned will be of that subclass. For example, for HTTP an HttpURLConnection will be returned, and for JAR a JarURLConnection will be returned.

openStream

InputStream openStream ()

Opens a connection to this URL and returns an InputStream for reading from that connection. This method is a shorthand for:

     openConnection().getInputStream()
 

sameFile

boolean sameFile (URL other)

Compares two URLs, excluding the fragment component.

Returns true if this URL and the other argument are equal without taking the fragment component into consideration.

setURLStreamHandlerFactory

void setURLStreamHandlerFactory (URLStreamHandlerFactory fac)

Sets an application's URLStreamHandlerFactory. This method can be called at most once in a given Java Virtual Machine.

The URLStreamHandlerFactory instance is used to construct a stream protocol handler from a protocol name.

If there is a security manager, this method first calls the security manager's checkSetFactory method to ensure the operation is allowed. This could result in a SecurityException.

toExternalForm

String toExternalForm ()

Constructs a string representation of this URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object.

toString

String toString ()

Constructs a string representation of this URL. The string is created by calling the toExternalForm method of the stream protocol handler for this object.

toURI

URI toURI ()

Returns a URI equivalent to this URL. This method functions in the same way as new URI (this.toString()).

Note, any URL instance that complies with RFC 2396 can be converted to a URI. However, some URLs that are not strictly in compliance can not be converted to a URI.

set

void set (String protocol, 
                String host, 
                int port, 
                String authority, 
                String userInfo, 
                String path, 
                String query, 
                String ref)

Sets the specified 8 fields of the URL. This is not a public method so that only URLStreamHandlers can modify URL fields. URLs are otherwise constant.

set

void set (String protocol, 
                String host, 
                int port, 
                String file, 
                String ref)

Sets the fields of the URL. This is not a public method so that only URLStreamHandlers can modify URL fields. URLs are otherwise constant.