Class URL
- All Implemented Interfaces:
Serializable
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:
Types of URL
In general, a URL can be broken into several parts. Consider the following example:
http://www.example.com/docs/resource1.html
The URL above indicates that the protocol to use is
http
(HyperText Transfer Protocol) and that the
information resides on a host machine named
www.example.com
. The information on that host
machine is named /docs/resource1.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.example.com:1080/docs/resource1.html
The syntax of URL
is defined by RFC 2396: Uniform
Resource Identifiers (URI): Generic Syntax, amended by RFC 2732: Format for
Literal IPv6 Addresses in URLs. The Literal IPv6 address format
also supports scope_ids. The syntax and usage of scope_ids is described
here.
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://www.example.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://www.example.com/index.html
it would be a shorthand for:FAQ.html
http://www.example.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.
Constructing instances of URL
The java.net.URL
constructors are deprecated.
Developers are encouraged to use java.net.URI
to parse
or construct a URL
. In cases where an instance of
java.net.URL
is needed to open a connection, URI
can be used
to construct or parse the URL string, possibly calling URI.parseServerAuthority()
to validate that the authority component
can be parsed as a server-based authority, and then calling
URI.toURL()
to create the URL
instance.
The URL constructors are specified to throw
MalformedURLException
but the actual parsing/validation
that is performed is implementation dependent. Some parsing/validation
may be delayed until later, when the underlying stream handler's implementation is called.
Being able to construct an instance of URL
doesn't
provide any guarantee about its conformance to the URL
syntax specification.
The URL class does not itself encode or decode any URL components
according to the escaping mechanism defined in RFC2396. It is the
responsibility of the caller to encode any fields, which need to be
escaped prior to calling URL, and also to decode any escaped fields,
that are returned from URL. Furthermore, because URL has no knowledge
of URL escaping, it does not recognise equivalence between the encoded
or decoded form of the same URL. For example, the two URLs:
http://foo.com/hello world/ and http://foo.com/hello%20worldwould be considered not equal to each other.
Note, the URI
class does perform escaping of its
component fields in certain circumstances. The recommended way
to manage the encoding and decoding of URLs is to use URI
,
and to convert between these two classes using toURI()
and
URI.toURL()
.
The URLEncoder
and URLDecoder
classes can also be
used, but only for HTML form encoding, which is not the same
as the encoding scheme defined in RFC2396.
- API Note:
-
Applications working with file paths and file URIs should take great
care to use the appropriate methods to convert between the two.
The
Path.of(URI)
factory method and theFile(URI)
constructor can be used to createPath
orFile
objects from a file URI.Path.toUri()
andFile.toURI()
can be used to create aURI
from a file path, which can be converted to URL usingURI.toURL()
. Applications should never try to construct or parse aURL
from the direct string representation of aFile
orPath
instance.Before constructing a
URL
from aURI
, and depending on the protocol involved, applications should consider validating whether the URI authority can be parsed as server-based.Some components of a URL or URI, such as userinfo, may be abused to construct misleading URLs or URIs. Applications that deal with URLs or URIs should take into account the recommendations advised in RFC3986, Section 7, Security Considerations.
All
URL
constructors may throwMalformedURLException
. In particular, if the underlyingURLStreamHandler
implementation rejects, or is known to reject, any of the parameters,MalformedURLException
may be thrown. Typically, a constructor that calls the stream handler's parseURL method may throwMalformedURLException
if the underlying stream handler implementation of that method throwsIllegalArgumentException
. However, which checks are performed, or not, by the stream handlers is implementation dependent, and callers should not rely on such checks for full URL validation. - Since:
- 1.0
- External Specifications
- See Also:
-
Constructor Summary
ConstructorDescriptionDeprecated.Deprecated.UseURI.toURL()
to construct an instance of URL.URL
(String protocol, String host, int port, String file, URLStreamHandler handler) Deprecated.Useof(URI, URLStreamHandler)
to construct an instance of URL associated with a custom protocol handler.Deprecated.UseURI.toURL()
to construct an instance of URL.Deprecated.UseURI.toURL()
to construct an instance of URL.URL
(URL context, String spec, URLStreamHandler handler) Deprecated.Useof(URI, URLStreamHandler)
to construct an instance of URL associated with a custom protocol handler. -
Method Summary
Modifier and TypeMethodDescriptionboolean
Compares this URL for equality with another object.Gets the authority part of thisURL
.final Object
Gets the contents of this URL.final Object
getContent
(Class<?>[] classes) Gets the contents of this URL.int
Gets the default port number of the protocol associated with thisURL
.getFile()
Gets the file name of thisURL
.getHost()
Gets the host name of thisURL
, if applicable.getPath()
Gets the path part of thisURL
.int
getPort()
Gets the port number of thisURL
.Gets the protocol name of thisURL
.getQuery()
Gets the query part of thisURL
.getRef()
Gets the anchor (also known as the "reference") of thisURL
.Gets the userInfo part of thisURL
.int
hashCode()
Creates an integer suitable for hash table indexing.static URL
of
(URI uri, URLStreamHandler handler) Creates a URL from a URI, as if by invokinguri.toURL()
, but associating it with the givenURLStreamHandler
, if allowed.Returns aURLConnection
instance that represents a connection to the remote object referred to by theURL
.openConnection
(Proxy proxy) Same asopenConnection()
, except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection.final InputStream
Opens a connection to thisURL
and returns anInputStream
for reading from that connection.boolean
Compares two URLs, excluding the fragment component.static void
Sets an application'sURLStreamHandlerFactory
.Constructs a string representation of thisURL
.toString()
Constructs a string representation of thisURL
.toURI()
Returns aURI
equivalent to this URL.
-
Constructor Details
-
URL
@Deprecated(since="20") public URL(String protocol, String host, int port, String file) throws MalformedURLException Deprecated.UseURI.toURL()
to construct an instance of URL. See the note on constructor deprecation for more details.Creates aURL
object from the specifiedprotocol
,host
,port
number, andfile
.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:- If the application has previously set up an instance of
URLStreamHandlerFactory
as the stream handler factory, then thecreateURLStreamHandler
method of that instance is called with the protocol string as an argument to create the stream protocol handler. - If no
URLStreamHandlerFactory
has yet been set up, or if the factory'screateURLStreamHandler
method returnsnull
, then the ServiceLoader mechanism is used to locate URLStreamHandlerProvider implementations using the system class loader. The order that providers are located is implementation specific, and an implementation is free to cache the located providers. A ServiceConfigurationError,Error
orRuntimeException
thrown from thecreateURLStreamHandler
, if encountered, will be propagated to the calling thread. ThecreateURLStreamHandler
method of each provider, if instantiated, is invoked, with the protocol string, until a provider returns non-null, or all providers have been exhausted. - If the previous step fails to find a protocol handler, the
constructor reads the value of the system property:
If the value of that system property is notjava.protocol.handler.pkgs
null
, it is interpreted as a list of packages separated by a vertical slash character '|
'. The constructor tries to load the class named:
where<package>.<protocol>.Handler
<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 ofURLStreamHandler
, then the next package in the list is tried. - If the previous step fails to find a protocol handler, then the
constructor tries to load a built-in protocol handler.
If this class does not exist, or if the class exists but it is not a
subclass of
URLStreamHandler
, then aMalformedURLException
is thrown.
Protocol handlers for the following protocols are guaranteed to exist on the search path:
http
https
file
jar
No validation of the inputs is performed by this constructor.
- Parameters:
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 host- Throws:
MalformedURLException
- if an unknown protocol or the port is a negative number other than -1, or if the underlying stream handler implementation rejects, or is known to reject, theURL
- External Specifications
- See Also:
- If the application has previously set up an instance of
-
URL
@Deprecated(since="20") public URL(String protocol, String host, String file) throws MalformedURLException Deprecated.UseURI.toURL()
to construct an instance of URL. See the note on constructor deprecation for more details.Creates a URL from the specifiedprotocol
name,host
name, andfile
name. The default port for the specified protocol is used.This constructor is equivalent to the four-argument constructor with the only difference of using the default port for the specified protocol. No validation of the inputs is performed by this constructor.
- Parameters:
protocol
- the name of the protocol to use.host
- the name of the host.file
- the file on the host.- Throws:
MalformedURLException
- if an unknown protocol is specified, or if the underlying stream handler implementation rejects, or is known to reject, theURL
- See Also:
-
URL
@Deprecated(since="20") public URL(String protocol, String host, int port, String file, URLStreamHandler handler) throws MalformedURLException Deprecated.Useof(URI, URLStreamHandler)
to construct an instance of URL associated with a custom protocol handler. See the note on constructor deprecation for more details.Creates aURL
object from the specifiedprotocol
,host
,port
number,file
, andhandler
. Specifying aport
number of-1
indicates that the URL should use the default port for the protocol. Specifying ahandler
ofnull
indicates that the URL should use a default stream handler for the protocol, as outlined for: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 aNetPermission("specifyStreamHandler")
permission. This may result in a SecurityException. No validation of the inputs is performed by this constructor.- Parameters:
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 hosthandler
- the stream handler for the URL.- Throws:
MalformedURLException
- if an unknown protocol or the port is a negative number other than -1, or if the underlying stream handler implementation rejects, or is known to reject, theURL
SecurityException
- if a security manager exists and itscheckPermission
method doesn't allow specifying a stream handler explicitly.- See Also:
-
URL
Deprecated.UseURI.toURL()
to construct an instance of URL. See the note on constructor deprecation for more details.Creates aURL
object from theString
representation.This constructor is equivalent to a call to the two-argument constructor with a
null
first argument.- Parameters:
spec
- theString
to parse as a URL.- Throws:
MalformedURLException
- if no protocol is specified, or an unknown protocol is found, orspec
isnull
, or the parsed URL fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throwsIllegalArgumentException
- See Also:
-
URL
Deprecated.UseURI.toURL()
to construct an instance of URL. See the note on constructor deprecation for more details.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" :
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 fragment and query parts present in the spec are used in the new URL.<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 occurrences of ".." and ".".
For a more detailed description of URL parsing, refer to RFC2396.
- Implementation Requirements:
- Parsing the URL includes calling the
parseURL
method on the selected handler. - Parameters:
context
- the context in which to parse the specification.spec
- theString
to parse as a URL.- Throws:
MalformedURLException
- if no protocol is specified, or an unknown protocol is found, orspec
isnull
, or the parsed URL fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throwsIllegalArgumentException
- See Also:
-
URL
@Deprecated(since="20") public URL(URL context, String spec, URLStreamHandler handler) throws MalformedURLException Deprecated.Useof(URI, URLStreamHandler)
to construct an instance of URL associated with a custom protocol handler. See the note on constructor deprecation for more details.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.- Implementation Requirements:
- Parsing the URL includes calling the
parseURL
method on the selected handler. - Parameters:
context
- the context in which to parse the specification.spec
- theString
to parse as a URL.handler
- the stream handler for the URL.- Throws:
MalformedURLException
- if no protocol is specified, or an unknown protocol is found, orspec
isnull
, or the parsed URL fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throwsIllegalArgumentException
SecurityException
- if a security manager exists and itscheckPermission
method doesn't allow specifying a stream handler.- See Also:
-
-
Method Details
-
of
Creates a URL from a URI, as if by invokinguri.toURL()
, but associating it with the givenURLStreamHandler
, if allowed.- API Note:
- Applications should consider performing additional integrity
checks before constructing a
URL
and opening a connection. See the API note in the class level API documentation. - Implementation Requirements:
- The implementation of this method includes calling the
parseURL
method on the selected handler. - Parameters:
uri
- theURI
from which the returnedURL
should be builthandler
- a custom protocol stream handler for the returnedURL
. Can benull
, in which case the default stream handler for the protocol if any, will be used.- Returns:
- a new
URL
instance created from the givenURI
and associated with the givenURLStreamHandler
, if any - Throws:
NullPointerException
- ifuri
isnull
IllegalArgumentException
- if no protocol is specified (the uri scheme isnull
), or if theURLStreamHandler
is notnull
and can not be set for the given protocolMalformedURLException
- if an unknown protocol is found, or the given URI fails to comply with the specific syntax of the associated protocol, or the underlying stream handler's parseURL method throwsIllegalArgumentException
SecurityException
- if a security manager exists and itscheckPermission
method doesn't allow specifying a stream handler- Since:
- 20
- See Also:
-
getQuery
Gets the query part of thisURL
.- Returns:
- the query part of this
URL
, ornull
if one does not exist - Since:
- 1.3
-
getPath
Gets the path part of thisURL
.- Returns:
- the path part of this
URL
, or an empty string if one does not exist - Since:
- 1.3
-
getUserInfo
Gets the userInfo part of thisURL
.- Returns:
- the userInfo part of this
URL
, ornull
if one does not exist - Since:
- 1.3
-
getAuthority
Gets the authority part of thisURL
.- Returns:
- the authority part of this
URL
- Since:
- 1.3
-
getPort
public int getPort()Gets the port number of thisURL
.- Returns:
- the port number, or -1 if the port is not set
-
getDefaultPort
public int getDefaultPort()Gets the default port number of the protocol associated with thisURL
. If the URL scheme or the URLStreamHandler for the URL do not define a default port number, then -1 is returned.- Returns:
- the port number
- Since:
- 1.4
-
getProtocol
-
getHost
Gets the host name of thisURL
, 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']'
).- Returns:
- the host name of this
URL
.
-
getFile
Gets the file name of thisURL
. The returned file portion will be the same asgetPath()
, plus the concatenation of the value ofgetQuery()
, if any. If there is no query portion, this method andgetPath()
will return identical results.- Returns:
- the file name of this
URL
, or an empty string if one does not exist
-
getRef
Gets the anchor (also known as the "reference") of thisURL
.- Returns:
- the anchor (also known as the "reference") of this
URL
, ornull
if one does not exist
-
equals
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.
Two hosts are considered equivalent if both host names can be resolved into the same IP addresses; else if either host name can't be resolved, the host names must be equal without regard to case; or both host names equal to null.
Since hosts comparison requires name resolution, this operation is a blocking operation.
Note: The defined behavior for
equals
is known to be inconsistent with virtual hosting in HTTP. -
hashCode
-
sameFile
Compares two URLs, excluding the fragment component.Returns
true
if thisURL
and theother
argument are equal without taking the fragment component into consideration.- Parameters:
other
- theURL
to compare against.- Returns:
true
if they reference the same remote object;false
otherwise.
-
toString
-
toExternalForm
Constructs a string representation of thisURL
. The string is created by calling thetoExternalForm
method of the stream protocol handler for this object.- Returns:
- a string representation of this object.
- See Also:
-
toURI
Returns aURI
equivalent to this URL. This method functions in the same way asnew 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.
- Returns:
- a URI instance equivalent to this URL.
- Throws:
URISyntaxException
- if this URL is not formatted strictly according to RFC2396 and cannot be converted to a URI.- Since:
- 1.5
-
openConnection
Returns aURLConnection
instance that represents a connection to the remote object referred to by theURL
.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.
- Returns:
- a
URLConnection
linking to the URL. - Throws:
IOException
- if an I/O exception occurs.- See Also:
-
openConnection
Same asopenConnection()
, except that the connection will be made through the specified proxy; Protocol handlers that do not support proxying will ignore the proxy parameter and make a normal connection. Invoking this method preempts the system's defaultProxySelector
settings.- Parameters:
proxy
- the Proxy through which this connection will be made. If direct connection is desired, Proxy.NO_PROXY should be specified.- Returns:
- a
URLConnection
to the URL. - Throws:
IOException
- if an I/O exception occurs.SecurityException
- if a security manager is present and the caller doesn't have permission to connect to the proxy.IllegalArgumentException
- will be thrown if proxy is null, or proxy has the wrong typeUnsupportedOperationException
- if the subclass that implements the protocol handler doesn't support this method.- Since:
- 1.5
- See Also:
-
openStream
Opens a connection to thisURL
and returns anInputStream
for reading from that connection. This method is a shorthand for:openConnection().getInputStream()
- Returns:
- an input stream for reading from the URL connection.
- Throws:
IOException
- if an I/O exception occurs.- See Also:
-
getContent
Gets the contents of this URL. This method is a shorthand for:openConnection().getContent()
- Returns:
- the contents of this URL.
- Throws:
IOException
- if an I/O exception occurs.- See Also:
-
getContent
Gets the contents of this URL. This method is a shorthand for:openConnection().getContent(classes)
- Parameters:
classes
- an array of Java types- Returns:
- the content object of this URL that is the first match of the types specified in the classes array. null if none of the requested types are supported.
- Throws:
IOException
- if an I/O exception occurs.- Since:
- 1.3
- See Also:
-
setURLStreamHandlerFactory
Sets an application'sURLStreamHandlerFactory
. 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.- Parameters:
fac
- the desired factory.- Throws:
Error
- if the application has already set a factory.SecurityException
- if a security manager exists and itscheckSetFactory
method doesn't allow the operation.- See Also:
-
URI.toURL()
to construct an instance of URL.