Is this a good case for the Strategy Pattern - csv

Question

I have the following inputs:
A CSV File
An array of grammar rules. The grammar rules are
basically metadata that tells me what which each column datatype
should be.
The output would return back to me a list of records that had any errors. So if column should be a date but I'm given the wrong format. I would return those rows.
The csv file would be something like this:
first_name,last_name,dob,age,
john,doe,2001/05/02
mary,jane,1968/04/01
Metadata:
column:first_name
type:string
column:dob
type:date
I was wondering if the strategy pattern would be the right choice. I was thinking of injecting the proper grammar (metadata) depending upon the file. I have multiple files I want to validate.

Answer 1

This problem needs the Validation Handlers (for your grammar rule). Looking at lower complexity level and expected extensions, I do not feel the need of any specific design pattern. I would suggest following simple OO approach. Alternatively depending upon expected dynamic behavior, COR can be incorporated by putting each Concrete Handler in a chain (COR). Pass each token in a chain so as to give opportunity to handlers in a chain till it gets handled.
public class Extractor {
public static void main(String[] args) {
// PREPARE TEMP_MAP_HANDLERS<Type,Handler>
Map<String, Handler> handlers = new HashMap<>();
handlers.put("FIRST_NAME",new NAMEHandler());
handlers.put("LAST_NAME",new NAMEHandler());
handlers.put("DOB",new DOBHandler());
handlers.put("AGE",new AGEHandler());
// READ THE HEADER
String header = "first_name,last_name,dob,age";// SAMPLE READ HEADER
// PREPARE LOOKUP<COL_INDEX, TYPE_HANDLER>
Map<Integer, Handler> metaHandlers = new HashMap<>();
String[] headerTokens = header.split(",");
for (int i = 0; i < headerTokens.length; i++) {
metaHandlers.put(i, handlers.get(headerTokens[i].toUpperCase()));
}
// DONE WITH TEMP HANDLER LOOKUP
// READ ACTUAL ROWS
// FOR EACH ROW IN FILE
String row = "joh*n,doe,2001/05/02";
String[] rowTokens = row.split(",");
for (int i = 0; i < rowTokens.length;i++) {
System.out.println(rowTokens[i]);
Handler handler = metaHandlers.get(i);
if (!handler.validate(rowTokens[i])){
// REPORT WRONG DATA
System.out.println("Wrong Token" + rowTokens[i]);
}
}
}
}
abstract class Handler {
abstract boolean validate (String field);
}
class NAMEHandler extends Handler{
#Override
boolean validate(String field) {
// Arbitrary rule - name should not contain *
return !field.contains("*");
}
}
class DOBHandler extends Handler{
#Override
boolean validate(String field) {
// Arbitrary rule - contains /
return field.contains("/");
}
}
class AGEHandler extends Handler{
#Override
boolean validate(String field) {
// TODO validate AGE
return true;
}
}