TargetConverter Base Class (Extends Converter)

Overview

The TargetConverter, derived from the Converter class, is the base class for the CSV, flat file, and EDI target converter classes developed in the next three chapters. The lists below summarize the major attributes and methods.

Attributes:

• RecordWriter Object

Methods:

• Constructor

• processDocument (virtual)

• processGroup

The processGroup method is listed here for completeness but will be developed in Chapter 8.

Method

Constructor

Similar to the SourceConverter's constructor, the TargetConverter's constructor is very basic.

Logic for the TargetConverter Constructor Method

Arguments:
  String File Description Document Name

Call base class constructor
Call loadFileDescriptionDocument from passed document

You will note that in this constructor, unlike the SourceConverter constructor, we load the file description document. This is because of differences in how we will process EDI files in Chapter 9. An EDI interchange that we read may have several different documents in it and may need several different file description documents. So, we don't want to load the file description document in the base class constructor. However, when we write an EDI interchange we'll just accept one document type as input. This is the same model we follow for CSV and flat files. We'll load the file description document in the base class target converter.

Derived Class Method

processDocument

As with the processFile method in the SourceConverter, this method is declared as a virtual method in the base class and implemented separately in each of the derived classes for our legacy formats. The general processing model is to read from multiple XML documents in multiple files and create a single output file in the legacy format. We'll also make our life somewhat easier by reading the files from a single directory rather than multiple directories. The listing below shows the general logic.

Logic for the TargetConverter processDocument Method

Arguments:
  DOM Document Input Document
Root Element <- Call Input Document's getDocumentElement method
Root Element Name <- Call Root Element's getTagName
IF (Root Element Name != Root Element Name from Grammar Element)
  Return Error
ENDIF
Child Element <- Get Root Element's firstChild, skipping over
    non-Element Nodes
DO for all Record Elements, starting with first child of Root
  Record Grammar Element <- Get Record Grammar Element from
      Document Grammar Element
  Call RecordWriter's parseRecord method, passing Record Element
      and Record Grammar Element
  Call RecordWriter's writeRecord method
ENDDO

That's the basic setup. Pretty simple, huh? Simple is good. Simple is robust, maintainable, and extensible.