将字符串转换为字节数组而不进行编码？

Question

So I have a string with Binary Data like this:

String lob = "ÿØÿà...";

I really have no control over this so I have to take it as it is. So I need to convert this as an InputStream without changing it, if I just do:

getBytes()

It will use the default encoding, how do I do this without any encoding or modification?

EdIT:

I can't fix this from the source. I do know the original data is a image loaded from HTML GET, but I don't know how it was encoded during transfer . All I have right now is a really long string and I need to convert it back and save it into a database.

Answer 1

There's no such concept as a conversion like that without encoding. You're converting between characters and bytes - those aren't the same thing, so a conversion is required, and the form of the conversion is precisely the encoding. Anything which claims to be converting without using an encoding is just assuming some specific encoding without necessarily knowing they're doing so.

If you want to get the original binary data, you need to find out what encoding was used to convert the bytes into a string to start with. You may find that ISO-8859-1 will work, but you really need to check.

At the same time, you should try very hard to change it to use something like base64. Converting arbitrary binary data to text and back like this is a recipe for disaster.

Answer 2

If it really is that your String contains binary data that was just erroneously put into a string instead of a byte-array, then there is quite a simple method of conversion:

byte[] target = new byte[lob.length()];
for(int i = 0; i < lob.length(); i++)
    target[i] = (byte)lob.charAt(i);

If this data is somehow textual, however, then Jon Skeet's answer is the right one.

(This is, by the way, the same as ISO-8859-1 encoding.)

Answer 3

Strings use UTF-16 encoding and to avoid conversion you can use this encoding and each 16-bit character is basic sent as is.

Assuming you are in a Little-Endian environment

out.write(lob.getBytes(StandardCharset.UTF_16LE));

All valid characters will be send without further encoding.

Note: binary data should not be stored in Strings unless you really know it safe to do this as not all 16-bit values are valid characters. A better way to store binary data is to use bytes.

Answer 4

I agree 100% with Jon Skeet. I'll add that Java does an implicit conversion of any String data to UTF-16, however that implicit conversion comes on top of an explicit conversion which was done by whoever is passing you that data (wether they know it or not), so using getBytes("UTF-16") isn't automatically going to work either, unless they state otherwise or you've checked so by yourself.

Knowing where that data comes from and what encoding it is in is the only way to convert it back properly.