Ancient Programming

I am working on a project where we need to manipulate fixed formatted text files. The fixed formatted files are used as protocol for interchanging data between some legacy mainframe systems. I have been looking for some already existing api for manipulating these fixed formatted data but couldn’t find any.

So this weekend I started implementing a solution based on some of the idea´s we got along the way.

Basics

I have a few goals for the api:

1. A line of text should be easily manipulated as a java object.
2. Should require a minimum of own code to manipulate the text string.
3. Use annotations to define attributes like:
   • Offset in text
   • The fixed length of the text
   • padding direction and padding character

The api usage could look something like this:

public interface Record {

  // use if you need a reference to the manipulated string - could be a constructor
  void initialize(StringBuffer buffer);

  // use if you don't need a reference to the manipulated string - could be a constructor
  void initialize(String string);

  String export(); //export string
}
...
public abstract class MyRecord implements Record {

  @FixedFormatField(offset = 10, length=20, paddingChar='0')
  public abstract void setMyInteger(Integer myInteger);

  @FixedFormatField(offset = 10, length=20, paddingChar='0')
  public abstract Integer getMyInteger();
}

And then a factory to create instances of the Record. Maybe annotations on fields would be nice as well as dublicating annotations for setter/getter is waste and could be error-prone.

This is the part I am working on at the moment and getting some hands-on experience with javassist. I will get back to that in another post.

Fixedformat4j

I have named the api fixedformat4j and I will opensource it as soon as I have something worth for others to use. Hopefully it won’t end up as one of my numerous 23% finished projects…