How to convert a regular string format (ascii?) to UTF-7 in JavaScript or Java?

Question

So I'm trying to understand how a special character normally seen as '<' could be converted to '+ADw-' in UTF-7.

Is there an online tool or a built in library in JavaScript or Java that can do this?

What is the math behind this? I know that UTF-7 uses 7bits to store the character, so I am guessing that the '+ADw-' is just the numerical representation of '<' in ASCII? Meaning, if you converted to '<' to a number, that would be equal to '+ADw-' as a number?

Thanks!

No, UTF-7 uses one byte to store a 7-bit value, which is either the entire codepoint or some of its 21 bits, depending on the codepoint being encoded. — Tom Blodget
– Tom Blodget, Commented Sep 8, 2015 at 22:42

wero · Accepted Answer · 2015-09-08 15:35:25Z

2

Java itself does not have UTF-7 support.

But that library provides a UTF-7 charset implementation and when you add its jar to your Java application you can simply write:

OutputStreamWriter out = new OutputStreamWriter(System.out, "UTF-7");
out.write("<");

to see how a string is translated into UTF-7.

answered Sep 8, 2015 at 15:35

wero

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6 Comments

eternalminerals.com Over a year ago

Hey I tried using that but when I looked in the source of the jutf7 library it doesn't have a OutputStreamWriter, it uses java.io.OutputStreamWriter: Using this code I get no result, but I didnt just include the jar though, I copied all the src into my Test project in eclipse:

eternalminerals.com Over a year ago

import java.io.IOException; import java.io.OutputStreamWriter; import java.io.UnsupportedEncodingException; public class Test { public static void main(String[] args) { OutputStreamWriter out; try { out = new OutputStreamWriter(System.out, "UTF-7"); out.write("<"); } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }

wero Over a year ago

Yes the OutputStreamWriter in my example is java.io.OutputStreamWriter. Copying the sources to your project might not be enough. If you look into the jutf7-1.0.0.jar there is also a file META-INF/services/java.nio.charset.spi.CharsetProvider which is needed to register the UTF-7 charset. Therefore include this file as resource to your project or simply use the jar.

eternalminerals.com Over a year ago

Following the usage info in the src, I get bad results too: java -jar jutf7-1.0.0.jar encode < The syntax of the command is incorrect. java -jar jutf7-1.0.0.jar encode a a C:\Downloads\jutf7-1.0.0\jutf7-1.0.0>java -jar jutf7-1.0.0.jar enc de b b C:\Downloads\jutf7-1.0.0\jutf7-1.0.0>java -jar jutf7-1.0.0.jar enc de ss ss C:\Downloads\jutf7-1.0.0\jutf7-1.0.0>java -jar jutf7-1.0.0.jar enc de 1 1 C:\Downloads\jutf7-1.0.0\jutf7-1.0.0>java -jar jutf7-1.0.0.jar enc de < The syntax of the command is incorrect.

eternalminerals.com Over a year ago

wero, thank you so much for your guidance. I added the jar AND the src to the build path of the sample project in eclipse but its still not displaying anything. I will continue to tinker around with this and keep you posted.

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