Develop Reference

Encode to UTF-8. Encode character eg. ö to ö

I want to encode a string in Android to UTF-8. For example this string:
Grüne Ähren beißen Flöhe
to
Grüne Ãhren beiÃen Flöhe
But no matter what I do I encode ü to ü or ü to %C3%BC (online often called 'raw URL encode').
Found solutions to convert to byte[] or URI.toASCIIString(). But non of them work for me.
UPDATE
I am participating in the eBay partner network and try to concat a searchword to my partner url.
The people of eBay must use a wrong character set, as UTF-8 URL encoded string don't work.
A searchword with UTF-8 URL encoding
(Grüne Ähren beißen Flöhe
to
Gr%C3%BCne%20%C3%84hren%20bei%C3%9Fen%20Fl%C3%B6he)
comes out to this result in the eBay searchbox:
If I encode my searchword with ISO_8859_1 it works (Grüne Ãhren beiÃen Flöhe):
Thank you very much community

What you essentially want is to convert a String to it's byte representation according to UTF-8 and interpret these bytes using a different Charset, such as ISO-8859-1.
This is usually the cause of many problems. You want to intentionally do what most developers do incorrectly (or they simply ignore the problems of charsets).
Since you just need this to work, use this piece of code:
byte[] bytes = "Grüne Ähren beißen Flöhe".getBytes("UTF-8");
String result = new String(bytes, "ISO-8859-1");
see it at work here.

Why do I have to encode a utf-8 parameter String to iso-Latin and then decode as utf-8 to get Java utf-8 String?

I have a Java servlet that takes a parameter String (inputString) that may contain Greek letters from a web page marked up as utf-8. Before I send it to a database I have to convert it to a new String (utf8String) as follows:
String utf8String = new String(inputString.getBytes("8859_1"), "UTF-8");
This works, but, as I hope will be appreciated, I hate doing something I don't understand, even if it works.
From the method description in the Java doc the getBytes() method "Encodes this String into a sequence of bytes using the named charset, storing the result into a new byte array" i.e. I am encoding it in 8859_1 — isoLatin. And from the Constructor description "Constructs a new String by decoding the specified array of bytes using the specified charset" i.e. decodes the byte array to utf-8.
Can someone explain to me why this is necessary?

My question is based on a misconception regarding the character set used for the HTTP request. I had assumed that because I marked up the web page from which the request was sent as UTF-8 the request would be sent as UTF-8, and so the Greek characters in the parameter sent to the servlet would be read as a UTF-8 String (‘inputString’ in my line of code) by the HttpRequest.getParameter() method. This is not the case.
HTTP requests are sent as ISO-8859-1 (POST) or ASCII (GET), which are generally the same. This is part of the URI Syntax specification — thanks to Andreas for pointing me to http://wiki.apache.org/tomcat/FAQ/CharacterEncoding where this is explained.
I had also forgotten that the encoding of Greek letters such as α for the request is URL-encoding, which produces %CE%B1. The getParameter() handles this by decoding it as two ISO-8859-1 characters, %CE and %B1 — Î and ± (I checked this).
I now understand why this needs to be turned into a byte array and the bytes interpreted as UTF-8. 0xCE does not represent a one-byte character in UTF-8 and hence it is addressed with the next byte, 0xB1, to be interpretted as α. (Î is 0xC3 0x8E and ± is 0xC2 0xB1 in UTF-8.)

When decoding, could you not create a class with a decoder method that takes the bytes [] as a parameter and
return it as a string? here is an example that i have used before.
public class Decoder
{
public String decode(byte[] bytes)
{
//Turns the bytes array into a string
String decodedString = new String(bytes);
return decodedString;
}
}
Try use this instead of .getBytes(). hope this works.

Converting string to byte[] returns wrong value (encoding?)

I read a byte[] from a file and convert it to a String:
byte[] bytesFromFile = Files.readAllBytes(...);
String stringFromFile = new String(bytesFromFile, "UTF-8");
I want to compare this to another byte[] I get from a web service:
String stringFromWebService = webService.getMyByteString();
byte[] bytesFromWebService = stringFromWebService.getBytes("UTF-8");
So I read a byte[] from a file and convert it to a String and I get a String from my web service and convert it to a byte[]. Then I do the following tests:
// works!
org.junit.Assert.assertEquals(stringFromFile, stringFromWebService);
// fails!
org.junit.Assert.assertArrayEquals(bytesFromFile, bytesFromWebService);
Why does the second assertion fail?

Other answers have covered the likely fact that the file is not UTF-8 encoded giving rise to the symptoms described.
However, I think the most interesting aspect of this is not that the byte[] assert fails, but that the assert that the string values are the same passes. I'm not 100% sure why this is, but I think the following trawl through the source code might give us the answer:
Looking at how new String(bytesFromFile, "UTF-8"); works - we see that the constructor calls through to StringCoding.decode()
This in turn, if supplied with tht UTF-8 character set, calls through to StringDecoder.decode()
This calls through to CharsetDecoder.decode() which decides what to do if the character is unmappable (which I guess will be the case if a non-UTF-8 character is presented)
In this case it uses an action defined by
private CodingErrorAction unmappableCharacterAction
= CodingErrorAction.REPORT;
Which means that it still reports the character it has decoded, even though it's technically unmappable.
I think this means that even when the code gets an umappable character, it substitutes its best guess - so I'm guessing that its best guess is correct and hence the String representations are the same under comparison, but the byte[] are no longer the same.
This hypothesis is kind of supported by the fact that the catch block for CharacterCodingException in StringCoding.decode() says:
} catch (CharacterCodingException x) {
// Substitution is always enabled,
// so this shouldn't happen

I don't understand it fully, but here's what I get so fare:
The problem is that the data contains some bytes which are not valid UTF-8 bytes as I know by the following check:
// returns false for my data!
public static boolean isValidUTF8(byte[] input) {
CharsetDecoder cs = Charset.forName("UTF-8").newDecoder();
try {
cs.decode(ByteBuffer.wrap(input));
return true;
}
catch(CharacterCodingException e){
return false;
}
}
When I change the encoding to ISO-8859-1 everything works fine. The strange thing (which a don't understand yet) is why my conversion (new String(bytesFromFile, "UTF-8");) doesn't throw any exception (like my isValidUTF8 method), although the data is not valid UTF-8.
However, I think I will go another and encode my byte[] in a Base64 string as I don't want more trouble with encoding.

The real problem in your code is that you don't know what the real file encoding.
When you read the string from the web service you get a sequence of chars; when you convert the string from chars to bytes the conversion is made right because you specify how to transform char in bytes with a specific encoding ("UFT-8"). when you read a text file you face a different problem. You have a sequence of bytes that needs to be converted to chars. In order to do it properly you must know how the chars where converted to bytes i.e. what is the file encoding. For files (unless specified) it's a platform constants; on windows the file are encoded in win1252 (which is very close to ISO-8859-1); on linux/unix it depends, I think UTF8 is the default.
By the way the web service call did a decond operation under the hood; the http call use an header taht defins how chars are encoded, i.e. how to read the bytes form the socket and transform then to chars. So calling a SOAP web service gives you back an xml (which can be marshalled into a Java object) with all the encoding operations done properly.
So if you must read chars from a File you must face the encoding issue; you can use BASE64 as you stated but you lose one of the main benefits of text files: the are human readable, easing debugging and developing.

Long string convert to UTF-8 throws exception

I am using GWT, and have a very long string from RichTextArea and I want to convert it to UTF-8 before sending to the server:
String content = new String(rta.getText().getBytes(), "UTF-8");
However this one throws an exception saying:
[Range Error]: Maximum call stack size exceeded
Is this a bug?

RichTextArea.getText returns a String. The operation you are doing to "convert to utf-8" is not correct. There is no need to convert a java String to any character encoding. The code you have is getting the bytes in the default character encoding of the platform and then interpreting them as utf-8. At best this is a lot of work to get back to the exact same String. At worst (say platform encoding of utf-16le) you mangle your String data completely.

Java Servlet Repsonse Set Content Lenght For CSV

Requirements
Downlading a CSV File
Code
I have a csvFormattedString like
String csvFormattedString = "\"Column_One\",\"Column_Two\"\n\"Row_Col1\",\"Row_Col2\"\n";
This CSV String is written to the reponse print writer using
response.getWriter().write(csvFormattedString);
I have set the headers as application-force-download and have set the charcter encoding to UTF-8.
I would like to send the response length back to the user as well.
The csvFormattedString.length() does not seem to be correct as some my characters get truncated

csvFormattedString.length() counts the characters.
Use s.getBytes("UTF-8").length to get the number of bytes used for that string represented as UTF-8.
You have to catch UnsupportedEncodingException in order to use getBytes(String encoding).