Java URL encoding of query string parameters

Question

Say I have a URL   http   example com query q    and I have a query entered by the user such as      random word   500 bank     I want the result to be a properly encoded URL   http   example com query q random 20word 20 A3500 20bank 20 24   What s the best way to achieve this  I tried URLEncoder and creating URI URL objects but none of them come out quite right

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URL url  new URL  http   example com query q random word   500 bank      URI uri   new URI url getProtocol    url getUserInfo    IDN toASCII url getHost     url getPort    url getPath    url getQuery    url getRef     String correctEncodedURL uri toASCIIString     System out println correctEncodedURL     Prints  http   example com query q random 20word 20 C2 A3500 20bank 20    What is happening here   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    For more info see  How to encode properly this URL   In some cases it is advisable to check if the url is already encoded  Also replace     encoded spaces with   20  encoded spaces     Here are some examples that will also work properly           in     http           com          out     http   xn--mgba3gch31f com             in     http   www example com   foo         out     http   www example com  E2 80 A5 foo            in     http   search barnesandnoble com booksearch first book pdf          out     http   search barnesandnoble com booksearch first 20book pdf             in     http   example com query q random word   500 bank            out     http   example com query q random 20word 20 C2 A3500 20bank 20       The solution passes around 100 of the testcases provided by Web Plattform Tests

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Using Spring s UriComponentsBuilder  UriComponentsBuilder          fromUriString url           build            encode            toUri

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In android I would use this code   Uri myUI   Uri parse   http   example com query   buildUpon   appendQueryParameter  q   random word A3500 bank 24   build      Where Uri is a android net Uri

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URLEncoder is the way to go  You only need to keep in mind to encode only the individual query string parameter name and or value  not the entire URL  for sure not the query string parameter separator character  amp  nor the parameter name-value separator character    String q    quot random word   500 bank   quot   String url    quot https   example com q  quot    URLEncoder encode q  StandardCharsets UTF 8    When you re still not on Java 10 or newer  then use StandardCharsets UTF 8 toString   as charset argument  or when you re still not on Java 7 or newer  then use  quot UTF-8 quot    Note that spaces in query parameters are represented by    not  20  which is legitimately valid  The  20 is usually to be used to represent spaces in URI itself  the part before the URI-query string separator character     not in query string  the part after     Also note that there are three encode   methods  One without Charset as second argument and another with String as second argument which throws a checked exception  The one without Charset argument is deprecated  Never use it and always specify the Charset argument  The javadoc even explicitly recommends to use the UTF-8 encoding  as mandated by RFC3986 and W3C   All other characters are unsafe and are first converted into one or more bytes using some encoding scheme  Then each byte is represented by the 3-character string  quot  xy quot   where xy is the two-digit hexadecimal representation of the byte  The recommended encoding scheme to use is UTF-8  However  for compatibility reasons  if an encoding is not specified  then the default encoding of the platform is used   See also   What every web developer must know about URL encoding

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Guava 15 has now added a set of straightforward URL escapers

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I found an easy solution to your question  I also wanted to use an encoded URL but nothing helped me    http   example com query q random 20word 20 A3500 20bank 20 24  to use String example    quot random word   500 bank   quot   you can you below code  String example    quot random word   500 bank   quot   String URL    quot http   example com query q  quot    example replaceAll  quot   quot   quot  20 quot

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I would not use URLEncoder  Besides being incorrectly named  URLEncoder has nothing to do with URLs   inefficient  it uses a StringBuffer instead of Builder and does a couple of other things that are slow  Its also way too easy to screw it up   Instead I would use URIBuilder or Spring s org springframework web util UriUtils encodeQuery or Commons Apache HttpClient  The reason being you have to escape the query parameters name  ie BalusC s answer q  differently than the parameter value    The only downside to the above  that I found out painfully  is that URL s are not a true subset of URI s    Sample code   import org apache http client utils URIBuilder   URIBuilder ub   new URIBuilder  http   example com query    ub addParameter  q    random word   500 bank       String url   ub toString        Result  http   example com query q random word  C2 A3500 bank  24   Since I m just linking to other answers I marked this as a community wiki  Feel free to edit

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In my case i just needed to pass the whole url and encode only the value of each parameters  I didn t find a common code to do that so      so i created this small method to do the job    public static String encodeUrl String url  throws Exception       if  url    null     url contains                 return url             List lt String gt  list   new ArrayList lt  gt         String rootUrl   url split        0             String paramsUrl   url replace rootUrl           List lt String gt  paramsUrlList   Arrays asList paramsUrl split   amp          for  String param   paramsUrlList            if  param contains                     String key   param split      0               String value   param replace key                         list add key          URLEncoder encode value   UTF-8                       else               list add param                        return rootUrl   StringUtils join list    amp        public static String decodeUrl String url  throws Exception       return URLDecoder decode url   UTF-8        It uses org apache commons lang3 StringUtils

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Here s a method you can use in your code to convert a url string and map of parameters to a valid encoded url string containing the query parameters   String addQueryStringToUrlString String url  final Map lt Object  Object gt  parameters  throws UnsupportedEncodingException       if  parameters    null            return url             for  Map Entry lt Object  Object gt  parameter   parameters entrySet               final String encodedKey   URLEncoder encode parameter getKey   toString     UTF-8            final String encodedValue   URLEncoder encode parameter getValue   toString     UTF-8             if   url contains                     url          encodedKey         encodedValue            else               url      amp     encodedKey         encodedValue                       return url

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Use this  URLEncoder encode query  StandardCharsets UTF 8 displayName      or this URLEncoder encode query   UTF-8    You can use the follwing code   String encodedUrl1   UriUtils encodeQuery query   UTF-8     not change  String encodedUrl2   URLEncoder encode query   UTF-8     changed String encodedUrl3   URLEncoder encode query  StandardCharsets UTF 8 displayName      changed  System out println  url1     encodedUrl1     n     url2     encodedUrl2     n     url3     encodedUrl3

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You need to first create a URI like   String urlStr    http   www example com CEREC   Materials  amp  Accessories IPS Empress   CAD pdf  URL url  new URL urlStr   URI uri   new URI url getProtocol    url getUserInfo    url getHost    url getPort    url getPath    url getQuery    url getRef       Then convert that Uri to ASCII string   urlStr uri toASCIIString      Now your url string is completely encoded first we did simple url encoding and then we converted it to ASCII String to make sure no character outside US-ASCII are remaining in string  This is exactly how browsers do

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Apache Http Components library provides a neat option for building and encoding query params -   With HttpComponents 4 x use -     URLEncodedUtils  For HttpClient 3 x use -     EncodingUtil

[java] Java URL encoding of query string parameters

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