URI

See also:

• RFC 2279: UTF-8, a transformation format of ISO 10646
• RFC 2373: IPv6 Addressing Architecture
• RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax
• RFC 2732: Format for Literal IPv6 Addresses in URLs

URI

public URI (String str)

Constructs a URI by parsing the given string.

This constructor parses the given string exactly as specified by the grammar in RFC 2396, Appendix A, except for the following deviations:

• An empty authority component is permitted as long as it is followed by a non-empty path, a query component, or a fragment component. This allows the parsing of URIs such as "file:///foo/bar", which seems to be the intent of RFC 2396 although the grammar does not permit it. If the authority component is empty then the user-information, host, and port components are undefined.

• Empty relative paths are permitted; this seems to be the intent of RFC 2396 although the grammar does not permit it. The primary consequence of this deviation is that a standalone fragment such as "#foo" parses as a relative URI with an empty path and the given fragment, and can be usefully resolved against a base URI.

• IPv4 addresses in host components are parsed rigorously, as specified by RFC 2732: Each element of a dotted-quad address must contain no more than three decimal digits. Each element is further constrained to have a value no greater than 255.

• Hostnames in host components that comprise only a single domain label are permitted to start with an alphanum character. This seems to be the intent of RFC 2396 section 3.2.2 although the grammar does not permit it. The consequence of this deviation is that the authority component of a hierarchical URI such as s://123, will parse as a server-based authority.

• IPv6 addresses are permitted for the host component. An IPv6 address must be enclosed in square brackets ('[' and ']') as specified by RFC 2732. The IPv6 address itself must parse according to RFC 2373. IPv6 addresses are further constrained to describe no more than sixteen bytes of address information, a constraint implicit in RFC 2373 but not expressible in the grammar.

• Characters in the other category are permitted wherever RFC 2396 permits escaped octets, that is, in the user-information, path, query, and fragment components, as well as in the authority component if the authority is registry-based. This allows URIs to contain Unicode characters beyond those in the US-ASCII character set.

URI

public URI (String scheme, 
                String ssp, 
                String fragment)

Constructs a URI from the given components.

A component may be left undefined by passing null.

This constructor first builds a URI in string form using the given components as follows:

1. Initially, the result string is empty.

2. If a scheme is given then it is appended to the result, followed by a colon character (':').

3. If a scheme-specific part is given then it is appended. Any character that is not a legal URI character is quoted.

4. Finally, if a fragment is given then a hash character ('#') is appended to the string, followed by the fragment. Any character that is not a legal URI character is quoted.

The resulting URI string is then parsed in order to create the new URI instance as if by invoking the URI(java.lang.String) constructor; this may cause a URISyntaxException to be thrown.

URI

public URI (String scheme, 
                String userInfo, 
                String host, 
                int port, 
                String path, 
                String query, 
                String fragment)

Constructs a hierarchical URI from the given components.

If a scheme is given then the path, if also given, must either be empty or begin with a slash character ('/'). Otherwise a component of the new URI may be left undefined by passing null for the corresponding parameter or, in the case of the port parameter, by passing -1.

This constructor first builds a URI string from the given components according to the rules specified in RFC 2396, section 5.2, step 7:

1. Initially, the result string is empty.

2. If a scheme is given then it is appended to the result, followed by a colon character (':').

3. If user information, a host, or a port are given then the string "//" is appended.

4. If user information is given then it is appended, followed by a commercial-at character ('@'). Any character not in the unreserved, punct, escaped, or other categories is quoted.

5. If a host is given then it is appended. If the host is a literal IPv6 address but is not enclosed in square brackets ('[' and ']') then the square brackets are added.

6. If a port number is given then a colon character (':') is appended, followed by the port number in decimal.

7. If a path is given then it is appended. Any character not in the unreserved, punct, escaped, or other categories, and not equal to the slash character ('/') or the commercial-at character ('@'), is quoted.

8. If a query is given then a question-mark character ('?') is appended, followed by the query. Any character that is not a legal URI character is quoted.

9. Finally, if a fragment is given then a hash character ('#') is appended, followed by the fragment. Any character that is not a legal URI character is quoted.

The resulting URI string is then parsed as if by invoking the URI(java.lang.String) constructor and then invoking the parseServerAuthority() method upon the result; this may cause a URISyntaxException to be thrown.

URI

public URI (String scheme, 
                String host, 
                String path, 
                String fragment)

Constructs a hierarchical URI from the given components.

A component may be left undefined by passing null.

This convenience constructor works as if by invoking the seven-argument constructor as follows:

new URI(scheme, null, host, -1, path, null, fragment);

URI

public URI (String scheme, 
                String authority, 
                String path, 
                String query, 
                String fragment)

Constructs a hierarchical URI from the given components.

If a scheme is given then the path, if also given, must either be empty or begin with a slash character ('/'). Otherwise a component of the new URI may be left undefined by passing null for the corresponding parameter.

This constructor first builds a URI string from the given components according to the rules specified in RFC 2396, section 5.2, step 7:

1. Initially, the result string is empty.

2. If a scheme is given then it is appended to the result, followed by a colon character (':').

3. If an authority is given then the string "//" is appended, followed by the authority. If the authority contains a literal IPv6 address then the address must be enclosed in square brackets ('[' and ']'). Any character not in the unreserved, punct, escaped, or other categories, and not equal to the commercial-at character ('@'), is quoted.

4. If a path is given then it is appended. Any character not in the unreserved, punct, escaped, or other categories, and not equal to the slash character ('/') or the commercial-at character ('@'), is quoted.

5. If a query is given then a question-mark character ('?') is appended, followed by the query. Any character that is not a legal URI character is quoted.

6. Finally, if a fragment is given then a hash character ('#') is appended, followed by the fragment. Any character that is not a legal URI character is quoted.

The resulting URI string is then parsed as if by invoking the URI(java.lang.String) constructor and then invoking the parseServerAuthority() method upon the result; this may cause a URISyntaxException to be thrown.

compareTo

public int compareTo (URI that)

Compares this URI to another object, which must be a URI.

When comparing corresponding components of two URIs, if one component is undefined but the other is defined then the first is considered to be less than the second. Unless otherwise noted, string components are ordered according to their natural, case-sensitive ordering as defined by the String.compareTo method. String components that are subject to encoding are compared by comparing their raw forms rather than their encoded forms.

The ordering of URIs is defined as follows:

• Two URIs with different schemes are ordered according the ordering of their schemes, without regard to case.

• A hierarchical URI is considered to be less than an opaque URI with an identical scheme.

• Two opaque URIs with identical schemes are ordered according to the ordering of their scheme-specific parts.

• Two opaque URIs with identical schemes and scheme-specific parts are ordered according to the ordering of their fragments.

• Two hierarchical URIs with identical schemes are ordered according to the ordering of their authority components:

  • If both authority components are server-based then the URIs are ordered according to their user-information components; if these components are identical then the URIs are ordered according to the ordering of their hosts, without regard to case; if the hosts are identical then the URIs are ordered according to the ordering of their ports.

  • If one or both authority components are registry-based then the URIs are ordered according to the ordering of their authority components.

• Finally, two hierarchical URIs with identical schemes and authority components are ordered according to the ordering of their paths; if their paths are identical then they are ordered according to the ordering of their queries; if the queries are identical then they are ordered according to the order of their fragments.

This method satisfies the general contract of the Comparable.compareTo method.

create

public static URI create (String str)

Creates a URI by parsing the given string.

This convenience factory method works as if by invoking the URI(java.lang.String) constructor; any URISyntaxException thrown by the constructor is caught and wrapped in a new IllegalArgumentException object, which is then thrown.

This method is provided for use in situations where it is known that the given string is a legal URI, for example for URI constants declared within in a program, and so it would be considered a programming error for the string not to parse as such. The constructors, which throw URISyntaxException directly, should be used situations where a URI is being constructed from user input or from some other source that may be prone to errors.

equals

public boolean equals (Object ob)

Tests this URI for equality with another object.

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

For two URIs to be considered equal requires that either both are opaque or both are hierarchical. Their schemes must either both be undefined or else be equal without regard to case. Their fragments must either both be undefined or else be equal.

For two opaque URIs to be considered equal, their scheme-specific parts must be equal.

For two hierarchical URIs to be considered equal, their paths must be equal and their queries must either both be undefined or else be equal. Their authorities must either both be undefined, or both be registry-based, or both be server-based. If their authorities are defined and are registry-based, then they must be equal. If their authorities are defined and are server-based, then their hosts must be equal without regard to case, their port numbers must be equal, and their user-information components must be equal.

When testing the user-information, path, query, fragment, authority, or scheme-specific parts of two URIs for equality, the raw forms rather than the encoded forms of these components are compared and the hexadecimal digits of escaped octets are compared without regard to case.

This method satisfies the general contract of the Object.equals method.

getAuthority

public String getAuthority ()

Returns the decoded authority component of this URI.

The string returned by this method is equal to that returned by the getRawAuthority method except that all sequences of escaped octets are decoded.

getFragment

public String getFragment ()

Returns the decoded fragment component of this URI.

The string returned by this method is equal to that returned by the getRawFragment method except that all sequences of escaped octets are decoded.

getHost

public String getHost ()

Returns the host component of this URI.

The host component of a URI, if defined, will have one of the following forms:

• A domain name consisting of one or more labels separated by period characters ('.'), optionally followed by a period character. Each label consists of alphanum characters as well as hyphen characters ('-'), though hyphens never occur as the first or last characters in a label. The rightmost label of a domain name consisting of two or more labels, begins with an alpha character.

• A dotted-quad IPv4 address of the form digit+.digit+.digit+.digit+, where no digit sequence is longer than three characters and no sequence has a value larger than 255.

• An IPv6 address enclosed in square brackets ('[' and ']') and consisting of hexadecimal digits, colon characters (':'), and possibly an embedded IPv4 address. The full syntax of IPv6 addresses is specified in RFC 2373: IPv6 Addressing Architecture.

getPath

public String getPath ()

Returns the decoded path component of this URI.

The string returned by this method is equal to that returned by the getRawPath method except that all sequences of escaped octets are decoded.

getPort

public int getPort ()

Returns the port number of this URI.

The port component of a URI, if defined, is a non-negative integer.

getQuery

public String getQuery ()

Returns the decoded query component of this URI.

The string returned by this method is equal to that returned by the getRawQuery method except that all sequences of escaped octets are decoded.

getRawAuthority

public String getRawAuthority ()

Returns the raw authority component of this URI.

The authority component of a URI, if defined, only contains the commercial-at character ('@') and characters in the unreserved, punct, escaped, and other categories. If the authority is server-based then it is further constrained to have valid user-information, host, and port components.

getRawFragment

public String getRawFragment ()

Returns the raw fragment component of this URI.

The fragment component of a URI, if defined, only contains legal URI characters.

getRawPath

public String getRawPath ()

Returns the raw path component of this URI.

The path component of a URI, if defined, only contains the slash character ('/'), the commercial-at character ('@'), and characters in the unreserved, punct, escaped, and other categories.

getRawQuery

public String getRawQuery ()

Returns the raw query component of this URI.

The query component of a URI, if defined, only contains legal URI characters.

getRawSchemeSpecificPart

public String getRawSchemeSpecificPart ()

Returns the raw scheme-specific part of this URI. The scheme-specific part is never undefined, though it may be empty.

The scheme-specific part of a URI only contains legal URI characters.

getRawUserInfo

public String getRawUserInfo ()

Returns the raw user-information component of this URI.

The user-information component of a URI, if defined, only contains characters in the unreserved, punct, escaped, and other categories.

getScheme

public String getScheme ()

Returns the scheme component of this URI.

The scheme component of a URI, if defined, only contains characters in the alphanum category and in the string "-.+". A scheme always starts with an alpha character.

The scheme component of a URI cannot contain escaped octets, hence this method does not perform any decoding.

getSchemeSpecificPart

public String getSchemeSpecificPart ()

Returns the decoded scheme-specific part of this URI.

The string returned by this method is equal to that returned by the getRawSchemeSpecificPart method except that all sequences of escaped octets are decoded.

getUserInfo

public String getUserInfo ()

Returns the decoded user-information component of this URI.

The string returned by this method is equal to that returned by the getRawUserInfo method except that all sequences of escaped octets are decoded.

hashCode

public int hashCode ()

Returns a hash-code value for this URI. The hash code is based upon all of the URI's components, and satisfies the general contract of the Object.hashCode method.

isAbsolute

public boolean isAbsolute ()

Tells whether or not this URI is absolute.

A URI is absolute if, and only if, it has a scheme component.

isOpaque

public boolean isOpaque ()

Tells whether or not this URI is opaque.

A URI is opaque if, and only if, it is absolute and its scheme-specific part does not begin with a slash character ('/'). An opaque URI has a scheme, a scheme-specific part, and possibly a fragment; all other components are undefined.

normalize

public URI normalize ()

Normalizes this URI's path.

If this URI is opaque, or if its path is already in normal form, then this URI is returned. Otherwise a new URI is constructed that is identical to this URI except that its path is computed by normalizing this URI's path in a manner consistent with RFC 2396, section 5.2, step 6, sub-steps c through f; that is:

1. All "." segments are removed.

2. If a ".." segment is preceded by a non-".." segment then both of these segments are removed. This step is repeated until it is no longer applicable.

3. If the path is relative, and if its first segment contains a colon character (':'), then a "." segment is prepended. This prevents a relative URI with a path such as "a:b/c/d" from later being re-parsed as an opaque URI with a scheme of "a" and a scheme-specific part of "b/c/d". (Deviation from RFC 2396)

A normalized path will begin with one or more ".." segments if there were insufficient non-".." segments preceding them to allow their removal. A normalized path will begin with a "." segment if one was inserted by step 3 above. Otherwise, a normalized path will not contain any "." or ".." segments.

parseServerAuthority

public URI parseServerAuthority ()

Attempts to parse this URI's authority component, if defined, into user-information, host, and port components.

If this URI's authority component has already been recognized as being server-based then it will already have been parsed into user-information, host, and port components. In this case, or if this URI has no authority component, this method simply returns this URI.

Otherwise this method attempts once more to parse the authority component into user-information, host, and port components, and throws an exception describing why the authority component could not be parsed in that way.

This method is provided because the generic URI syntax specified in RFC 2396 cannot always distinguish a malformed server-based authority from a legitimate registry-based authority. It must therefore treat some instances of the former as instances of the latter. The authority component in the URI string "//foo:bar", for example, is not a legal server-based authority but it is legal as a registry-based authority.

In many common situations, for example when working URIs that are known to be either URNs or URLs, the hierarchical URIs being used will always be server-based. They therefore must either be parsed as such or treated as an error. In these cases a statement such as

URI u= new URI(str).parseServerAuthority();

can be used to ensure that u always refers to a URI that, if it has an authority component, has a server-based authority with proper user-information, host, and port components. Invoking this method also ensures that if the authority could not be parsed in that way then an appropriate diagnostic message can be issued based upon the exception that is thrown.

relativize

public URI relativize (URI uri)

Relativizes the given URI against this URI.

The relativization of the given URI against this URI is computed as follows:

1. If either this URI or the given URI are opaque, or if the scheme and authority components of the two URIs are not identical, or if the path of this URI is not a prefix of the path of the given URI, then the given URI is returned.

2. Otherwise a new relative hierarchical URI is constructed with query and fragment components taken from the given URI and with a path component computed by removing this URI's path from the beginning of the given URI's path.

resolve

public URI resolve (URI uri)

Resolves the given URI against this URI.

If the given URI is already absolute, or if this URI is opaque, then the given URI is returned.

If the given URI's fragment component is defined, its path component is empty, and its scheme, authority, and query components are undefined, then a URI with the given fragment but with all other components equal to those of this URI is returned. This allows a URI representing a standalone fragment reference, such as "#foo", to be usefully resolved against a base URI.

Otherwise this method constructs a new hierarchical URI in a manner consistent with RFC 2396, section 5.2; that is:

1. A new URI is constructed with this URI's scheme and the given URI's query and fragment components.

2. If the given URI has an authority component then the new URI's authority and path are taken from the given URI.

3. Otherwise the new URI's authority component is copied from this URI, and its path is computed as follows:

   1. If the given URI's path is absolute then the new URI's path is taken from the given URI.

   2. Otherwise the given URI's path is relative, and so the new URI's path is computed by resolving the path of the given URI against the path of this URI. This is done by concatenating all but the last segment of this URI's path, if any, with the given URI's path and then normalizing the result as if by invoking the normalize method.

The result of this method is absolute if, and only if, either this URI is absolute or the given URI is absolute.

resolve

public URI resolve (String str)

Constructs a new URI by parsing the given string and then resolving it against this URI.

This convenience method works as if invoking it were equivalent to evaluating the expression resolve(URI.create(str)).

toASCIIString

public String toASCIIString ()

Returns the content of this URI as a US-ASCII string.

If this URI does not contain any characters in the other category then an invocation of this method will return the same value as an invocation of the toString method. Otherwise this method works as if by invoking that method and then encoding the result.

toString

public String toString ()

Returns the content of this URI as a string.

If this URI was created by invoking one of the constructors in this class then a string equivalent to the original input string, or to the string computed from the originally-given components, as appropriate, is returned. Otherwise this URI was created by normalization, resolution, or relativization, and so a string is constructed from this URI's components according to the rules specified in RFC 2396, section 5.2, step 7.

toURL

public URL toURL ()

Constructs a URL from this URI.

This convenience method works as if invoking it were equivalent to evaluating the expression new URL(this.toString()) after first checking that this URI is absolute.