Question

In one app, I have a task to create files that will be used by a third party. Actually there are three distinct types of content in the files:

1. List of employee cards to send data to the third party app;
2. List of employee cards to collect biometry;
3. Interval of numbers.

For now I have just one class called FileGenerator (generic, bad name I think) that receives the data and creates a file with some name convention (code of clock, type of file, date and hour).

There’s a good design pattern to ensure that the file name convention will remains and to split the generation of files in specific classes for each type of file?

There’s a good way to reuse the code that generates the file (don’t repeating myself in the specific classes)?

This is part of the existing class:

class FileGenerator {
    private List<String> contentOfFile;
    private String fileName;

    //I - include employees
    //C - change employees
    //R - remove employees
    //B - collect biometry
    //N - interval of numbers
    private String option;

    private void getFileName(){ ... } //this assure the file name convention
    public void generate(){ ... } //this generate the file with content

}

---

What I think so far:

1. Create one abstract class to hold the name convention. And to write the content to a file.
2. Create a factory class that will know all the types of files (factory is a good pattern to use here?).
3. Implement concrete classes to the types of files to define which content will be written.

Answer 1

More or less what you said:

1-The template method pattern for writing the file. I am thinking something like this:

public abstract class EmployeeCardFileGenerator {
   /**
   * @return the generated file name
   */
   public abstract String getFileName(/*any params you need to get the file name*/);

   /**
   * @return the line corresponding to the given data record
   */
   public abstract String getLine(EmployeeCardData data);

   /**
   * @return the header to be appended at the beginning of the file
   */      
   public abstract String getHeader(/*any header params*/);

   /**
   * @return the footer to be appended at the end of the file
   */
   public abstract String getFooter(/*any footer params*/);

   public void generateFile(/*any params*/) {
      List<EmployeeCardData> data = queryData();

      File f = createFile();
      PrintWriter pw = getWriter(f);
      pw.println(getHeader());

      for(EmployeeCardData ec : data) {
          pw.println(getLine(ec));
      }

      pw.println(getFooter());

      cleanup();
   }
}

2- You would have different implementations of these, dispensed by a factory.