Question

How can I “modify” an InputStream? I have a file as input, I would like to modify some variable and forward a new InputStream.

For example, the initial InputStream contains Hello ${var}. Then I want to “modify” this InputStream with var = “world”, resulting an InputStream Hello world.

What’s the best practice to do this? Thanks.

Answer 1

The java.io is one and all decorator pattern. Make use of it and create a class which extends InputStream (maybe DataInputStream or better, some Reader since you’re actually interested in characters, not in bytes, but ala), add a constructor which takes the original InputStream and override the read() methods to read the original stream in, buffer it to a certain degree (e.g. from ${ until with firstnext }) and then determine the key and return the modified data instead.

If you call your new class FormattedInputStream or so, then you could return new FormattedInputStream(originalInputStream) to the enduser instead and have the enduser still just assign and use it as an InputStream.