Java模式，用于生成和解析流中的数据

Question

I have certain protocol that I need to parse or generate. The parsing takes an InputStream and produce different type of objects depending the byte stream. The generator takes different inputs and spit out an OutputStream that allows writing to a target stream. Before reading / writing to the stream there might be some header variables that needs to be initialized.

For code right now looks something like follows:

// Parser.
DataX parsed = DataX.parse(new ByteInputStream(new byte [] {..}));
// Access short field of DataX.
System.out.println(parsed.getX() + parsed.getY()); // data in the header.
// Access some long field by spitting InputStream.
System.out.println(parsed.buildInputStream().readFully()); // data as bytes.

// Generator.
OutputStream outstream = 
   DataX.Generator(new FileOutputStream('output')).setX(x).setY(y).build();
// Write data.
outstream.write(new byte[] {...});

DataX extends a class Data that implements two methods deserialize and serialize as abstract method which will eventually be called somewhere inside parse() and Generator() .

This is a self-made design pattern, so I would like to ask if this makes sense and whether there is a more Java-ist way to do this kind of thing ?

---

Edit: The reason the stream needs to be incorporate is because the data might be huge (such as a file) and will not be feasible/desirable to store it entirely in the memory.

Answer 1

In general it is a good idea to keep data (header values) and its presentation (streams) separate.

Some component accepts streams ( Factory method pattern) and returns plain objects.

Those objects are serialized to streams via a different component later on.

It shouldn't matter if it is a stream at the moment. If later you want to work with Json objects - the design doesn't need to change dramatically.

Answer 2

I think a synmetrical pattern is easy to understand.

// Parser
DataX header = new DataX();   // uninitialized header
InputStream is = header.input(new FileInputStream(...));
// At this point header is initialized.
// user reads data from is.

// Generator
DataX header = new DataX();   // uninitialized header
header.setX(x).setY(y);       // initialize header
OutputStream os = header.output(new FileOutputStream(...));
// At this point header is written to os.
// user writes data to os.