Class URLNormalizer
- java.lang.Object
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- com.networknt.url.URLNormalizer
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- All Implemented Interfaces:
Serializable
public class URLNormalizer extends Object implements Serializable
The general idea behind URL normalization is to make different URLs "equivalent" (i.e. eliminate URL variations pointing to the same resource). To achieve this,
URLNormalizertakes a URL and modifies it to its most basic or standard form (for the context in which it is used). Of courseURLNormalizercan simply be used as a generic URL manipulation tool for your needs.You would typically "build" your normalized URL by invoking each method of interest, in the relevant order, using a similar approach:
String url = "Http://Example.com:80//foo/index.html"; URL normalizedURL = new URLNormalizer(url) .lowerCaseSchemeHost() .removeDefaultPort() .removeDuplicateSlashes() .removeDirectoryIndex() .addWWW() .toURL(); System.out.println(normalizedURL.toString()); // Output: http://www.example.com/foo/Several normalization methods implemented come from the RFC 3986 standard. These standards and several more normalization techniques are very well summarized on the Wikipedia article titled URL Normalization. This class implements most normalizations described on that article and borrows several of its examples, as well as a few additional ones.
The normalization methods available can be broken down into three categories:
Preserving Semantics
The following normalizations are part of the RFC 3986 standard and should result in equivalent URLs (one that identifies the same resource):
Convert scheme and host to lower caseConvert escape sequence to upper caseDecode percent-encoded unreserved charactersRemoving default portsURL-Encode non-ASCII charactersEncode spaces to plus sign
Usually Preserving Semantics
The following techniques will generate a semantically equivalent URL for the majority of use cases but are not enforced as a standard.
Not Preserving Semantics
These normalizations will fail to produce semantically equivalent URLs in many cases. They usually work best when you have a good understanding of the web site behind the supplied URL and whether for that site, which normalizations can be be considered to produce semantically equivalent URLs or not.
Remove directory indexRemove fragment (#)Replace IP with domain nameUnsecure schema (https → http)Secure schema (http → https)Remove duplicate slashesRemove "www."Add "www."Sort query parametersRemove empty query parametersRemove trailing question mark (?)Remove session IDs
Refer to each methods below for description and examples (or click on a normalization name above).
- Author:
- Pascal Essiembre
- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description URLNormalizer(String url)Create a newURLNormalizerinstance.URLNormalizer(URL url)Create a newURLNormalizerinstance.
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Method Summary
All Methods Instance Methods Concrete Methods Deprecated Methods Modifier and Type Method Description URLNormalizeraddDirectoryTrailingSlash()Adds a trailing slash (/) to a URL ending with a directory.URLNormalizeraddDomainTrailingSlash()Adds a trailing slash (/) right after the domain for URLs with no path, before any fragment (#) or query string (?).URLNormalizeraddTrailingSlash()Deprecated.Since 1.11.0, useaddDirectoryTrailingSlash()URLNormalizeraddWWW()Adds "www." domain name prefix.URLNormalizerdecodeUnreservedCharacters()Decodes percent-encoded unreserved characters.URLNormalizerencodeNonURICharacters()Encodes all characters that are not supported characters in a URI (not to confuse with URL), as defined by the RFC 3986 standard.URLNormalizerencodeSpaces()Encodes space characters into plus signs (+) if they are part of the query string.URLNormalizerlowerCaseSchemeHost()Converts the scheme and host to lower case.URLNormalizerremoveDefaultPort()Removes the default port (80 for http, and 443 for https).URLNormalizerremoveDirectoryIndex()Removes directory index files.URLNormalizerremoveDotSegments()Removes the unnecessary "." and ".." segments from the URL path.URLNormalizerremoveDuplicateSlashes()Removes duplicate slashes.URLNormalizerremoveEmptyParameters()Removes empty parameters.URLNormalizerremoveFragment()Removes the URL fragment (from the "#" character until the end).URLNormalizerremoveSessionIds()Removes a URL-based session id.URLNormalizerremoveTrailingHash()Removes trailing hash character ("#").URLNormalizerremoveTrailingQuestionMark()Removes trailing question mark ("?").URLNormalizerremoveTrailingSlash()Removes any trailing slash (/) from a URL, before fragment (#) or query string (?).URLNormalizerremoveWWW()Removes "www." domain name prefix.URLNormalizerreplaceIPWithDomainName()Replaces IP address with domain name.URLNormalizersecureScheme()Convertshttpscheme tohttps.URLNormalizersortQueryParameters()Sorts query parameters.StringtoString()Returns the normalized URL as string.URItoURI()Returns the normalized URL asURI.URLtoURL()Returns the normalized URL asURL.URLNormalizerunsecureScheme()Convertshttpsscheme tohttp.URLNormalizerupperCaseEscapeSequence()Converts letters in URL-encoded escape sequences to upper case.
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Constructor Detail
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URLNormalizer
public URLNormalizer(URL url)
Create a newURLNormalizerinstance.- Parameters:
url- the url to normalize
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URLNormalizer
public URLNormalizer(String url)
Create a new
URLNormalizerinstance.Since 1.8.0, spaces in URLs are no longer converted to + automatically. Use
encodeNonURICharacters()orencodeSpaces().- Parameters:
url- the url to normalize
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Method Detail
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lowerCaseSchemeHost
public URLNormalizer lowerCaseSchemeHost()
Converts the scheme and host to lower case.HTTP://www.Example.com/ → http://www.example.com/- Returns:
- this instance
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upperCaseEscapeSequence
public URLNormalizer upperCaseEscapeSequence()
Converts letters in URL-encoded escape sequences to upper case.http://www.example.com/a%c2%b1b → http://www.example.com/a%C2%B1b- Returns:
- this instance
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decodeUnreservedCharacters
public URLNormalizer decodeUnreservedCharacters()
Decodes percent-encoded unreserved characters.http://www.example.com/%7Eusername/ → http://www.example.com/~username/- Returns:
- this instance
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encodeNonURICharacters
public URLNormalizer encodeNonURICharacters()
Encodes all characters that are not supported characters in a URI (not to confuse with URL), as defined by the RFC 3986 standard. This includes all non-ASCII characters.
Since this method also encodes spaces to the plus sign (+), there is no need to also invoke
encodeSpaces().http://www.example.com/^a [b]/ → http://www.example.com/%5Ea+%5Bb%5D/- Returns:
- this instance
- Since:
- 1.8.0
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encodeSpaces
public URLNormalizer encodeSpaces()
Encodes space characters into plus signs (+) if they are part of the query string. Spaces part of the URL path are percent-encoded to %20.
To encode all non-ASCII characters (including spaces), use
encodeNonURICharacters()instead.http://www.example.com/a b c → http://www.example.com/a+b+c- Returns:
- this instance
- Since:
- 1.8.0
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removeDefaultPort
public URLNormalizer removeDefaultPort()
Removes the default port (80 for http, and 443 for https).http://www.example.com:80/bar.html → http://www.example.com/bar.html- Returns:
- this instance
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addDirectoryTrailingSlash
public URLNormalizer addDirectoryTrailingSlash()
Adds a trailing slash (/) to a URL ending with a directory. A URL is considered to end with a directory if the last path segment, before fragment (#) or query string (?), does not contain a dot, typically representing an extension.
Please Note: URLs do not always denote a directory structure and many URLs can qualify to this method without truly representing a directory. Adding a trailing slash to these URLs could potentially break its semantic equivalence.
http://www.example.com/alice → http://www.example.com/alice/- Returns:
- this instance
- Since:
- 1.11.0 (renamed from "addTrailingSlash")
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addDomainTrailingSlash
public URLNormalizer addDomainTrailingSlash()
Adds a trailing slash (/) right after the domain for URLs with no path, before any fragment (#) or query string (?).
Please Note: Adding a trailing slash to URLs could potentially break its semantic equivalence.
http://www.example.com → http://www.example.com/- Returns:
- this instance
- Since:
- 1.12.0
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addTrailingSlash
@Deprecated public URLNormalizer addTrailingSlash()
Deprecated.Since 1.11.0, useaddDirectoryTrailingSlash()Adds a trailing slash (/) to a URL ending with a directory. A URL is considered to end with a directory if the last path segment, before fragment (#) or query string (?), does not contain a dot, typically representing an extension.
Please Note: URLs do not always denote a directory structure and many URLs can qualify to this method without truly representing a directory. Adding a trailing slash to these URLs could potentially break its semantic equivalence.
http://www.example.com/alice → http://www.example.com/alice/- Returns:
- this instance
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removeTrailingSlash
public URLNormalizer removeTrailingSlash()
Removes any trailing slash (/) from a URL, before fragment (#) or query string (?).
Please Note: Removing trailing slashes form URLs could potentially break their semantic equivalence.
http://www.example.com/alice/ → http://www.example.com/alice- Returns:
- this instance
- Since:
- 1.11.0
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removeDotSegments
public URLNormalizer removeDotSegments()
Removes the unnecessary "." and ".." segments from the URL path.
As of 2.3.0, the algorithm used to remove the dot segments is the one prescribed by RFC3986.
http://www.example.com/../a/b/../c/./d.html → http://www.example.com/a/c/d.htmlPlease Note: URLs do not always represent a clean hierarchy structure and the dots/double-dots may have a different signification on some sites. Removing them from a URL could potentially break its semantic equivalence.
- Returns:
- this instance
- See Also:
URI.normalize()
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removeDirectoryIndex
public URLNormalizer removeDirectoryIndex()
Removes directory index files. They are often not needed in URLs.
http://www.example.com/a/index.html → http://www.example.com/a/Index files must be the last URL path segment to be considered. The following are considered index files:
- index.html
- index.htm
- index.shtml
- index.php
- default.html
- default.htm
- home.html
- home.htm
- index.php5
- index.php4
- index.php3
- index.cgi
- placeholder.html
- default.asp
Please Note: There are no guarantees a URL without its index files will be semantically equivalent, or even be valid.
- Returns:
- this instance
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removeFragment
public URLNormalizer removeFragment()
Removes the URL fragment (from the "#" character until the end).
http://www.example.com/bar.html#section1 → http://www.example.com/bar.html- Returns:
- this instance
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replaceIPWithDomainName
public URLNormalizer replaceIPWithDomainName()
Replaces IP address with domain name. This is often not reliable due to virtual domain names and can be slow, as it has to access the network.
http://208.77.188.166/ → http://www.example.com/- Returns:
- this instance
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unsecureScheme
public URLNormalizer unsecureScheme()
Converts
httpsscheme tohttp.https://www.example.com/ → http://www.example.com/- Returns:
- this instance
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secureScheme
public URLNormalizer secureScheme()
Converts
httpscheme tohttps.http://www.example.com/ → https://www.example.com/- Returns:
- this instance
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removeDuplicateSlashes
public URLNormalizer removeDuplicateSlashes()
Removes duplicate slashes. Two or more adjacent slash ("/") characters will be converted into one.
http://www.example.com/foo//bar.html → http://www.example.com/foo/bar.html- Returns:
- this instance
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removeWWW
public URLNormalizer removeWWW()
Removes "www." domain name prefix.
http://www.example.com/ → http://example.com/- Returns:
- this instance
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addWWW
public URLNormalizer addWWW()
Adds "www." domain name prefix.
http://example.com/ → http://www.example.com/- Returns:
- this instance
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sortQueryParameters
public URLNormalizer sortQueryParameters()
Sorts query parameters.
http://www.example.com/?z=bb&y=cc&z=aa → http://www.example.com/?y=cc&z=bb&z=aa- Returns:
- this instance
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removeEmptyParameters
public URLNormalizer removeEmptyParameters()
Removes empty parameters.
http://www.example.com/display?a=b&a=&c=d&e=&f=g → http://www.example.com/display?a=b&c=d&f=g- Returns:
- this instance
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removeTrailingQuestionMark
public URLNormalizer removeTrailingQuestionMark()
Removes trailing question mark ("?").
http://www.example.com/display? → http://www.example.com/display- Returns:
- this instance
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removeSessionIds
public URLNormalizer removeSessionIds()
Removes a URL-based session id. It removes PHP (PHPSESSID), ASP (ASPSESSIONID), and Java EE (jsessionid) session ids.
http://www.example.com/servlet;jsessionid=1E6FEC0D14D044541DD84D2D013D29ED?a=b → http://www.example.com/servlet?a=bPlease Note: Removing session IDs from URLs is often a good way to have the URL return an error once invoked.
- Returns:
- this instance
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removeTrailingHash
public URLNormalizer removeTrailingHash()
Removes trailing hash character ("#").
http://www.example.com/path# → http://www.example.com/pathThis only removes the hash character if it is the last character. To remove an entire URL fragment, use
removeFragment().- Returns:
- this instance
- Since:
- 1.13.0
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toString
public String toString()
Returns the normalized URL as string.
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