I'm using Apache BCEL to dynamically create java classes that will each have its own associated image. These generated class implement the following interface:
interface ImageOwner {
byte[] getImage();
}
When dynamically implementing the 'getImage' method, I could generate bytecodes to create/return the byte array when the method is invoked, but I would rather just return a reference to the byte array if possible. Is it possible to store raw data inside a java class file?
I'm really not sure here, because it seems too simple a question, but for completeness, this will do what I think you want to do:
public class ImageOwnerImpl implements ImageOwner {
// A literal byte array. Tedious, but you could write code
// to auto-generate this source from a file
private byte[] imageByteArray = new byte[] { -128, 127, ...etc };
public byte[] getImage() {
return imageByteArray;
}
}
This is a literal byte array, which answers your question of "how to store the bytes in the class file".
Most folks would load the image bytes from a file at runtime in the constructor, however you may have some special need that warrants this approach
After some research, the best way I found to achieve my needs was to base64 encode the image data and use the constant pool to store the resulting String. Even with the =~ 30% loss, it seems better than using the constructor or other methods to initialize a byte array field.
The only constants you can store in the constant pool are Ints, Floats, Longs, Doubles, Strings, and Classes. You're best bet is to just store it as a string and convert it to a Byte[] at run time. There is no need to base64 encode them, as strings can handle null characters, as long as you apply the proper modified unicode encoding.
Just define an Impl class that has a static initialiser that loads the raw data from a file that is included in your jar and loaded via the classloader.
You could just store it as a byte array the syntax for array in BCEL is
[B
for byte array
[java.lang.String
for a string array etc.
