We Keep Coding

URL encode/decode on file name replace spaces with +, need alternative.

My product is a web application.
I have files that I upload and download later on, to/from my server.
I am using java.net.URLDecoder.decode() when uploading files with unicode characters and java.net.URLDecoder.encode() when downloading files in order to save the file name and finally return it to the client as expected with no question marks and stuff (?????) .
The problem is that if the file name consists spaces then the encode/decode replace them with + character which is perfectly normal because that's their business implementation, but clearly as you can understand it does not fit to my purpose.
The question is what alternative do I have to overcome this situation?
Is there build-in method for that or 3rd party package?

You could also convert a space to %20.
See: URL encoding the space character: + or %20?
There are also various other Java libraries that do URL encoding, with %20. Here are a two examples:
Guava:
UrlEscapers.urlPathSegmentEscaper().escape(urlToEscape);
Spring Framework:
UriUtils.encodePath(urlToEscape, Charsets.UTF_8.toString());

You don't tell where this filename is used. The characters to encode will be different whether, for instance, it is in a URI query string or fragment part.
You probably want to have a look at Guava's (15.0+) Escapers; and, in particular here, UnicodeEscaper implementations and its derived class PercentEscaper. Guava already provides a few of them usable in various parts of URLs.
EDIT: here is how to do with Guava:
public final class FilenameEscaper
extends PercentEscaper
{
public PercentEscaper()
{
super("", false);
}
}
Done! See here. Of course, you may want to declare that some more characters than the default ones are safe.
Also have a look at RFC 5987 to make a better encoder.

This worked for me:
URLEncoder.encode(someString, "UTF-8").replace("+", "%20");

I found the cure!
I was just needed to use java.net.URI for that:
public static String encode(String urlString) throws UnsupportedEncodingException
{
try
{
URI uri = new URI(urlString);
return uri.toASCIIString();
}
catch (URISyntaxException e)
{
e.printStackTrace();
}
}
The toASCIIString() escapes the special characters so when the string arrives to the browser it is shown correctly.

Had the same problem with spaces. Combination of URL and URI solved it:
URL url = new URL("file:/E:/Program Files/IBM/SDP/runtimes/base");
URI uri = new URI(url.getProtocol(), url.getUserInfo(), url.getHost(), url.getPort(), url.getPath(), url.getQuery(), url.getRef());
* Please note that URLEncoder is used for web forms application/x-www-form-urlencoded mime-type - not http network addresses.
* Source: https://stackoverflow.com/a/749829/435605

Java API/util to find and replace unsafe characters with their percent encoded forms?

Does anyone know of a decent Java API/util to find and replace unsafe characters in a URL with their percent-encoded forms?

"http://google.com?" + URLEncoder.encode("...", "UTF-8");
See javadocs.
One should add the expected character encoding.

See Java - Convert String to valid URI object for pure Java style:
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();
Beware that it handles protocols available to Java natively. Otherwise you may need to register your own one like "s3" for Amazon S3 URIs.

how to replace brackets in url with bracket encoding?

I need a regex pattern that will find and replace brackets in urls to its urls encoding.
For example a base url like:
http://www.mysite.com/bla/blabla/abc[1].txt
will be turned to:
http://www.mysite.com/bla/blabla/abc%5B1%5D.txt
can anyone help please?
EDIT1:
i originaly use commons-httpclient to access this kind of urls.
when I use the first URL I get an "escaped absolute path no valid" exception.
I can't use URLENCODER because when I use it, I get a "host parameter is null" exception.

The following line should do the trick
String s = URLEncoder.encode("http://www.mysite.com/bla/blabla/abc[1].txt", "UTF-8");

Have you tried URLEncoder.encode?
in the java.net.URLEncoder package.
EDIT:
Ok i see... you cannot pass an entire URL to URLEncoder. URLEncoder is mostly used to encode query parameters.
try this instead:
URI uri = new URI("http", "www.mysite.com", "/bla/blabla/abc[1].txt",null);
System.out.println(uri.toASCIIString());

Encoding an URL sent to a server (not in query)

I need to be testing my server for several URLs daily since these URLs are updated by my users - and this will be dine in Java. However, these URLs contains strange characters (like the german umlaut). Basicly what I am doing is:
for every URL in the list to check
URL u = new URL(the_url);
u.openConnection(..);
// read the content and handle it
Now, what Ive found is that org.apache.commons.codec.net.URLCodec is fine for encoding string to paste into the QueryString, it is not as suitable to encode strange URLs into their hex counterparts. Here are some examples of URLs:
http:// www.example com/u/überraum-03/
http:// www.example com/u/são-paulo-dude/
http:// www.example com/u/håkon-hellström/
The desired result for the first would be;
http:// www.example com/u/%c3%9berraum-03/
Are there any library in the Apache Commons or java itself, to convert special character in the ACTUAL url (not querystring - and therefore not replace the same kind of characters) ?
Thank you for your time.
Edited
Firefox translates "yr.no/place/Norway/Nordland/Moskenes/Å/data.html"; into "yr.no/place/Norway/Nordland/Moskenes/%C3%85/data.html" (try this by entering the first URL, press enter, then copy the url into a document). It is this effect that I am looking for - since this is the actual translation. What is most likely happening is either FF knows Å is a bad thing, it tries multiple versions or it accepts the servers "Location" header; either way - there is a tranformation from "Å" to "%C3%85" on only a subset of the URL. This is the function we need.
Edited
I just verified that the code given by commentor does not work sadly. As an example, try this:
try{
String urlStr = "http://www.yr.no/place/Norway/Nordland/Moskenes/Å/data.html";
URL u=new URL(urlStr);
URI uri = new URI(u.getProtocol(),
u.getUserInfo(), u.getHost(), u.getPort(),
u.getPath(), u.getQuery(),
null); // removing ref
URL urlObj = uri.toURL();
HttpURLConnection connection = (HttpURLConnection) urlObj.openConnection();
connection.setInstanceFollowRedirects(false);
connection.connect();
for (int i=0;i<connection.getHeaderFields().size();i++)
System.out.println(connection.getHeaderFieldKey(i)+": "+connection.getHeaderField(i));
System.exit(0);
}catch(Exception e){e.printStackTrace();};
Will yield a 404 error - strangely enough the encoded part does also not work.

If you need a URL that is a valid URI (RFC 2396 compliant) you can create one like this in Java
String urlString = "http://www.example.com/u/håkon-hellström/";
URL url = new URL(urlString);
URI uri = new URI(url.getProtocol(),url.getAuthority(), url.getPath(), url.getQuery(), url.getRef());
url = new URL(uri.toASCIIString());
That being said all three sample strings you provided are RFC 2396 compliant and do not need to be encoded. I am assuming the spaces in the authority part of the URLs you provided are typos.
EDIT:
I updated the code block above. By using URI.toASCIIString() you can limit the resulting URI to only US-ASCII characters (other characters are encoded). The resulting string can then be used to create a new, valid URL.
http://www.example.com/u/håkon-hellström/
changes to
http://www.example.com/u/h%C3%A5kon-hellstr%C3%B6m/

Invalid URI with Chinese characters (Java)

Having trouble setting up a URL connection with Chinese characters in the URL. It works with Latin characters:
String xstr = "维也纳恩斯特哈佩尔球场" ;
URI uri = new URI("http","ajax.googleapis.com","/ajax/services/language/detect","v=1.0&q="+xstr,null);
URL url = uri.toURL();
URLConnection connection = url.openConnection();
InputStream is = connection.getInputStream() ;
The getInputStream() call results in:
java.lang.IllegalArgumentException: Invalid uri 'http://ajax.googleapis.com/ajax/services/language/detect?v=1.0&q=???????????': Invalid query

The problem is caused by the fact that URI.toURL() doesn't percent-encode non-ASCII characters. Use the following instead:
URL url = new URL(uri.toASCIIString());

axtavt's answer above saved me from insanity, thanks! Just one comment (I could not figure out how to comment below the answer:)
If you start with a URL, you need to encode quotes before you build the URI:
String s = "your_url?with=\"quotes\"";
URI su = new URI (s.replaceAll("\"", "%22");
URL ur = new URL( su.toASCIIString());

I think it is related to the "UTF-8" charset. Have a look at this topic to learn more and also this chinese in java

Per the URI RFC (see section 2.4), non-US-ASCII characters aren't valid in a URI. You must encode them.