HTTP URL Address Encoding in Java

Question

My Java standalone application gets a URL  which points to a file  from the user and I need to hit it and download it  The problem I am facing is that I am not able to encode the HTTP URL address properly     Example    URL   http   search barnesandnoble com booksearch first book pdf  java net URLEncoder encode url toString     ISO-8859-1      returns me   http 3A 2F 2Fsearch barnesandnoble com 2Fbooksearch 2Ffirst book pdf   But  what I want is  http   search barnesandnoble com booksearch first 20book pdf    space replaced by  20   I guess URLEncoder is not designed to encode HTTP URLs    The JavaDoc says  Utility class for HTML form encoding     Is there any other way to do this

User · Answer

Please be warned that most of the answers above are INCORRECT.

The URLEncoder class, despite is name, is NOT what needs to be here. It's unfortunate that Sun named this class so annoyingly. URLEncoder is meant for passing data as parameters, not for encoding the URL itself.

In other words, "http://search.barnesandnoble.com/booksearch/first book.pdf" is the URL. Parameters would be, for example, "http://search.barnesandnoble.com/booksearch/first book.pdf?parameter1=this&param2=that". The parameters are what you would use URLEncoder for.

The following two examples highlights the differences between the two.

The following produces the wrong parameters, according to the HTTP standard. Note the ampersand (&) and plus (+) are encoded incorrectly.

uri = new URI("http", null, "www.google.com", 80, 
"/help/me/book name+me/", "MY CRZY QUERY! +&+ :)", null);

// URI: http://www.google.com:80/help/me/book%20name+me/?MY%20CRZY%20QUERY!%20+&+%20:)

The following will produce the correct parameters, with the query properly encoded. Note the spaces, ampersands, and plus marks.

uri = new URI("http", null, "www.google.com", 80, "/help/me/book name+me/", URLEncoder.encode("MY CRZY QUERY! +&+ :)", "UTF-8"), null);

// URI: http://www.google.com:80/help/me/book%20name+me/?MY+CRZY+QUERY%2521+%252B%2526%252B+%253A%2529

User · Answer

How about   public String UrlEncode String in      String retVal        try       retVal   URLEncoder encode in    UTF8      catch  UnsupportedEncodingException ex        Log get   exception Log Level Error   urlEncode    ex      return retVal

User · Answer

I had the same problem  Solved this by unsing    android net Uri encode urlString           It encodes the string but skips     and

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You can also use GUAVA and path escaper  UrlEscapers urlFragmentEscaper   escape relativePath

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I read the previous answers to write my own method because I could not have something properly working using the solution of the previous answers  it looks good for me but if you can find URL that does not work with this  please let me know   public static URL convertToURLEscapingIllegalCharacters String toEscape  throws MalformedURLException  URISyntaxException               URL url   new URL toEscape               URI uri   new URI url getProtocol    url getUserInfo    url getHost    url getPort    url getPath    url getQuery    url getRef                   if a   is included in the toEscape string  it will be re-encoded to  25 and we don t want re-encoding  just encoding             return new URL uri toString   replace   25

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I took the content above and changed it around a bit   I like positive logic first  and I thought a HashSet might give better performance than some other options  like searching through a String   Although  I m not sure if the autoboxing penalty is worth it  but if the compiler optimizes for ASCII chars  then the cost of boxing will be low           Replaces any character not specifically unreserved to an equivalent     percent sequence      param s     return     public static String encodeURIcomponent String s        StringBuilder o   new StringBuilder        for  char ch   s toCharArray              if  isSafe ch                 o append ch                     else               o append                   o append toHex ch   16                o append toHex ch   16                        return o toString       private static char toHex int ch        return  char  ch  lt  10    0    ch    A    ch - 10         https   tools ietf org html rfc3986 section-2 3 public static final HashSet lt Character gt  UnreservedChars   new HashSet lt Character gt  Arrays asList           A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z            a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t   u   v   w   x   y   z            0   1   2   3   4   5   6   7   8   9            -                 public static boolean isSafe char ch        return UnreservedChars contains ch

User · Answer

Maybe can try UriUtils in org springframework web util  UriUtils encodeUri input   UTF-8

User · Answer

I agree with Matt  Indeed  I ve never seen it well explained in tutorials  but one matter is how to encode the URL path  and a very different one is how to encode the parameters which are appended to the URL  the query part  behind the     symbol   They use similar encoding  but not the same   Specially for the encoding of the white space character  The URL path needs it to be encoded as  20  whereas the query part allows  20 and also the     sign  The best idea is to test it by ourselves against our Web server  using a Web browser   For both cases  I ALWAYS would encode COMPONENT BY COMPONENT  never the whole string  Indeed URLEncoder allows that for the query part  For the path part you can use the class URI  although in this case it asks for the entire string  not a single component   Anyway  I believe that the best way to avoid these problems is to use a personal non-conflictive design  How  For example  I never would name directories or parameters using other characters than a-Z  A-Z  0-9 and     That way  the only need is to encode the value of every parameter  since it may come from an user input and the used characters are unknown

User · Answer

The java net URI class can help  in the documentation of URL you find     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 an URI   Use one of the constructors with more than one argument  like   URI uri   new URI       http         search barnesandnoble com          booksearch first book pdf       null   URL url   uri toURL      or String request   uri toString       the single-argument constructor of URI does NOT escape illegal characters       Only illegal characters get escaped by above code - it does NOT escape non-ASCII characters  see fatih s comment   The toASCIIString method can be used to get a String only with US-ASCII characters     URI uri   new URI       http         search barnesandnoble com          booksearch          null   String request   uri toASCIIString        For an URL with a query like http   www google com ig api weather S  o Paulo  use the 5-parameter version of the constructor     URI uri   new URI           http             www google com              ig api            weather S  o Paulo           null   String request   uri toASCIIString

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There is still a problem if you have got an encoded       2F  in your URL   RFC 3986 - Section 2 2 says   If data for a URI component would conflict with a reserved character s purpose as a delimiter  then the conflicting data must be percent-encoded before the URI is formed    RFC 3986 - Section 2 2   But there is an Issue with Tomcat       http   tomcat apache org security-6 html - Fixed in Apache Tomcat 6 0 10      important  Directory traversal CVE-2007-0450      Tomcat permits        2F  and   5C                  The following Java system properties   have been added to Tomcat to provide   additional control of the handling of   path delimiters in URLs  both options   default to false           org apache tomcat util buf UDecoder ALLOW ENCODED SLASH    true false   org apache catalina connector CoyoteAdapter ALLOW BACKSLASH    true false         Due to the impossibility to guarantee   that all URLs are handled by Tomcat as   they are in proxy servers  Tomcat   should always be secured as if no   proxy restricting context access was   used       Affects  6 0 0-6 0 9   So if you have got an URL with the  2F character  Tomcat returns   400 Invalid URI  noSlash   You can switch of the bugfix in the Tomcat startup script   set JAVA OPTS  JAVA OPTS   LOGGING CONFIG    -Dorg apache tomcat util buf UDecoder ALLOW ENCODED SLASH true

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Unfortunately  org apache commons httpclient util URIUtil is deprecated  and the replacement org apache commons codec net URLCodec does coding suitable for form posts  not in actual URL s  So I had to write my own function  which does a single component  not suitable for entire query strings that have   s and  amp  s   public static String encodeURLComponent final String s      if  s    null          return            final StringBuilder sb   new StringBuilder       try         for  int i   0  i  lt  s length    i                final char c   s charAt i          if    c  gt    A    amp  amp   c  lt    Z         c  gt    a    amp  amp   c  lt    z                   c  gt    0    amp  amp   c  lt    9                  c     -        c              c             c                          sb append c                 else                 final byte   bytes         c  getBytes  UTF-8             for  byte b   bytes                      sb append                  int upper      int  b   gt  gt  4   amp  0xf            sb append Integer toHexString upper  toUpperCase Locale US               int lower     int  b   amp  0xf            sb append Integer toHexString lower  toUpperCase Locale US                                 return sb toString          catch  UnsupportedEncodingException uee          throw new RuntimeException  UTF-8 unsupported     uee

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If you have a URL  you can pass url toString   into this method   First decode  to avoid double encoding  for example  encoding a space results in  20 and encoding a percent sign results in  25  so double encoding will turn a space into  2520    Then  use the URI as explained above  adding in all the parts of the URL  so that you don t drop the query parameters    public URL convertToURLEscapingIllegalCharacters String string       try           String decodedURL   URLDecoder decode string   UTF-8            URL url   new URL decodedURL           URI uri   new URI url getProtocol    url getUserInfo    url getHost    url getPort    url getPath    url getQuery    url getRef              return uri toURL           catch  Exception ex            ex printStackTrace            return null

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i use this  org apache commons text StringEscapeUtils escapeHtml4  my text    amp   lt   gt       add this dependecy    lt dependency gt           lt groupId gt org apache commons lt  groupId gt           lt artifactId gt commons-text lt  artifactId gt           lt version gt 1 8 lt  version gt       lt  dependency gt

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URLEncoding can encode HTTP URLs just fine  as you ve unfortunately discovered   The string you passed in   http   search barnesandnoble com booksearch first book pdf   was correctly and completely encoded into a URL-encoded form   You could pass that entire long string of gobbledigook that you got back as a parameter in a URL  and it could be decoded back into exactly the string you passed in   It sounds like you want to do something a little different than passing the entire URL as a parameter   From what I gather  you re trying to create a search URL that looks like  http   search barnesandnoble com booksearch whateverTheUserPassesIn    The only thing that you need to encode is the  whateverTheUserPassesIn  bit  so perhaps all you need to do is something like this   String url    http   search barnesandnoble com booksearch             URLEncoder encode userInput  UTF-8      That should produce something rather more valid for you

User · Answer

Yeah URL encoding is going to encode that string so that it would be passed properly in a url to a final destination   For example you could not have http   stackoverflow com url http   yyy com   UrlEncoding the parameter would fix that parameter value   So i have two choices for you    Do you have access to the path separate from the domain   If so you may be able to simply UrlEncode the path  However  if this is not the case then option 2 may be for you  Get commons-httpclient-3 1   This has a class URIUtil   System out println URIUtil encodePath  http   example com x y    ISO-8859-1       This will output exactly what you are looking for  as it will only encode the path part of the URI   FYI  you ll need commons-codec and commons-logging for this method to work at runtime

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In addition to the Carlos Heuberger s reply  if a different than the default  80  is needed  the 7 param constructor should be used   URI uri   new URI           http           null     this is for userInfo          www google com           8080     port number as int           ig api            weather S  o Paulo           null   String request   uri toASCIIString

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If anybody doesn t want to add a dependency to their project  these functions may be helpful   We pass the  path  part of our URL into here   You probably don t want to pass the full URL in as a parameter  query strings need different escapes  etc           Percent-encodes a string so it s suitable for use in a URL Path  not a query string   form encode  which uses   for spaces  etc      public static String percentEncode String encodeMe        if  encodeMe    null            return               String encoded   encodeMe replace        25        encoded   encoded replace        20        encoded   encoded replace        21        encoded   encoded replace        23        encoded   encoded replace        24        encoded   encoded replace   amp      26        encoded   encoded replace        27        encoded   encoded replace        28        encoded   encoded replace        29        encoded   encoded replace        2A        encoded   encoded replace        2B        encoded   encoded replace        2C        encoded   encoded replace        2F        encoded   encoded replace        3A        encoded   encoded replace        3B        encoded   encoded replace        3D        encoded   encoded replace        3F        encoded   encoded replace        40        encoded   encoded replace        5B        encoded   encoded replace        5D        return encoded            Percent-decodes a string  such as used in a URL Path  not a query string   form encode  which uses   for spaces  etc      public static String percentDecode String encodeMe        if  encodeMe    null            return               String decoded   encodeMe replace   21             decoded   decoded replace   20             decoded   decoded replace   23             decoded   decoded replace   24             decoded   decoded replace   26     amp         decoded   decoded replace   27             decoded   decoded replace   28             decoded   decoded replace   29             decoded   decoded replace   2A             decoded   decoded replace   2B             decoded   decoded replace   2C             decoded   decoded replace   2F             decoded   decoded replace   3A             decoded   decoded replace   3B             decoded   decoded replace   3D             decoded   decoded replace   3F             decoded   decoded replace   40             decoded   decoded replace   5B             decoded   decoded replace   5D             decoded   decoded replace   25             return decoded      And tests    Test public void testPercentEncode Decode         assertEquals     percentDecode percentEncode null         assertEquals     percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals   amp    percentDecode percentEncode   amp           assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode              assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode             assertEquals      percentDecode percentEncode                 Get a little complex     assertEquals        percentDecode percentEncode               assertEquals  a d     percentDecode percentEncode  a d            assertEquals         percentDecode percentEncode                assertEquals   21 20 2A 20 27 20 28 20 25 20 29 20 3B 20 3A 20 40 20 26 20 3D 20 2B 20 24 20 2C 20 2F 20 3F 20 23 20 5B 20 5D 20 25                       percentEncode                     amp                              assertEquals                     amp                        percentDecode                        21 20 2A 20 27 20 28 20 25 20 29 20 3B 20 3A 20 40 20 26 20 3D 20 2B 20 24 20 2C 20 2F 20 3F 20 23 20 5B 20 5D 20 25          assertEquals   23456   percentDecode percentEncode   23456

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You can use a function like this  Complete and modify it to your need               Encode URL  except           amp          characters          param url to encode         param encodingCharset url encoding charset         return encoded URL         throws UnsupportedEncodingException             public static String encodeUrl  String url  String encodingCharset  throws UnsupportedEncodingException              return new URLCodec   encode url  encodingCharset  replace   3A        replace   2F        replace   3F        replace   3D        replace   26     amp             Example of use    String urlToEncode     http   www growup com folder int  rieur-   vendre o 4   Utils encodeUrl  urlToEncode    UTF-8     The result is   http   www growup com folder int C3 A9rieur- C3 A0 vendre o 4

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Use the following standard Java solution  passes around 100 of the testcases provided by Web Plattform Tests    0  Test if URL is already encoded   1  Split URL into structural parts  Use java net URL  for it   2   Encode each structural part properly   3  Use IDN toASCII putDomainNameHere  to Punycode encode the host name    4  Use java net URI toASCIIString   to percent-encode  NFC encoded unicode -  better would be NFKC      Find more here  https   stackoverflow com a 49796882 1485527

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a solution i developed and much more stable than any other   public class URLParamEncoder        public static String encode String input            StringBuilder resultStr   new StringBuilder            for  char ch   input toCharArray                  if  isUnsafe ch                     resultStr append                       resultStr append toHex ch   16                    resultStr append toHex ch   16                  else                   resultStr append ch                                   return resultStr toString               private static char toHex int ch            return  char   ch  lt  10    0    ch    A    ch - 10              private static boolean isUnsafe char ch            if  ch  gt  128    ch  lt  0              return true          return      amp          lt  gt     indexOf ch   gt   0

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I develop a library that serves this purpose  galimatias  It parses URL the same way web browsers do  That is  if a URL works in a browser  it will be correctly parsed by galimatias   In this case      Parse io mola galimatias URL parse       http   search barnesandnoble com booksearch first book pdf    toString     Will give you  http   search barnesandnoble com booksearch first 20book pdf  Of course this is the simplest case  but it ll work with anything  way beyond java net URI   You can check it out at  https   github com smola galimatias

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I ve created a new project to help construct HTTP URLs  The library will automatically URL encode path segments and query parameters   You can view the source and download a binary at https   github com Widen urlbuilder  The example URL in this question   new UrlBuilder  search barnesandnoble com    booksearch first book pdf   toString     produces  http   search barnesandnoble com booksearch first 20book pdf

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I m going to add one suggestion here aimed at Android users   You can do this which avoids having to get any external libraries   Also  all the search replace characters solutions suggested in some of the answers above are perilous and should be avoided     Give this a try   String urlStr    http   abc dev domain com 0007AC ads 800x480 15sec h 264 mp4   URL url   new URL urlStr   URI uri   new URI url getProtocol    url getUserInfo    url getHost    url getPort    url getPath    url getQuery    url getRef     url   uri toURL      You can see that in this particular URL  I need to have those spaces encoded so that I can use it for a request     This takes advantage of a couple features available to you in Android classes   First  the URL class can break a url into its proper components so there is no need for you to do any string search replace work   Secondly  this approach takes advantage of the URI class feature of properly escaping components when you construct a URI via components rather than from a single string   The beauty of this approach is that you can take any valid url string and have it work without needing any special knowledge of it yourself

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