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simple-data-processing-framework

A simple framework for easy line-by-line data processing.

Introduction

Main interface of this framework is DataProcessor. Data processors are input-output machines which read input from same InputStream or Reader and write output to an OutputStream or a Writer. The framework contains some abstract classes for the most common scenarios (AbstractLineByLineDataProcessor, AbstractLinePatternDataProcessor etc.).

Simplest usage of a data processor is to read data from standard input and write to standard output:

new YourDataProcessor().process(System.in, System.out);

Also, this is the way how you can "standardize" your solution for Google Code Jam (see https://code.google.com/codejam/resources/quickstart-guide).

Process line by line

Simplest way to process a text file is to handle each line separately. Extend AbstractLineByLineDataProcessor for this:

public class AddLineNumbers extends AbstractLineByLineDataProcessor {
    
    @Override
    protected String processLine(int lineIndex, String inputLine) {
        return (lineIndex + 1) + ": " + inputLine;
    }

}

This data processor will insert line number before each line:

String input = "some line\nan other line\nthird line";
StringWriter outputWriter = new StringWriter();
new AddLineNumbers().process(new StringReader(input), outputWriter);;
System.out.println(outputWriter.toString());

Output:

1: some line
2: an other line
3: third line

When your input and output are String, no need to use any reader and writer, because StringDataProcessorWrapper performs the work with the boilerplate code in the background. This is especially useful for testing.

So the latest code snippet could be replaced with this:

String input = "some line\nan other line\nthird line";
System.out.println(new StringDataProcessorWrapper(new AddLineNumbers()).process(input));

This produces exactly the same output.

Process header and multiline input items

TODO

Parse numeric and other values

TODO

Process binary file

You can process binary files too:

class DigestDataProcessor extends AbstractDataProcessor {

    private final String algorithm;

    public DigestDataProcessor(String algorithm) {
        this.algorithm = algorithm;
    }

    @Override
    public void process(InputStream inputStream, OutputStream outputStream) throws IOException {
        MessageDigest messageDigest;
        try {
            messageDigest = MessageDigest.getInstance(algorithm);
        } catch (NoSuchAlgorithmException e) {
            throw new IOException(algorithm + " not supported!", e);
        }

        DigestInputStream digestInputStream = new DigestInputStream(inputStream, messageDigest);
        while (digestInputStream.read(new byte[1024]) >= 0);
        byte[] bytes = messageDigest.digest();

        char[] characters = new char[bytes.length * 2];
        char[] charArray = "0123456789abcdef".toCharArray();
        for (int i = 0; i < bytes.length; i++) {
            byte b = bytes[i];
            int byteValue = b & 0xFF;
            characters[i * 2] = charArray[byteValue >>> 4];
            characters[i * 2 + 1] = charArray[byteValue & 0x0F];
        }

        outputStream.write(new String(characters).getBytes(StandardCharsets.ISO_8859_1));
    }

}

For example, when you need the SHA1-sum of a file:

ByteArrayOutputStream out = new ByteArrayOutputStream();
new DigestDataProcessor("SHA1").process(new FileInputStream("/path/to/a-file"), out);
System.out.println(out.toString());

Using the GUI

TODO