How to Create a CSV File with Custom Column Headers and Positions Using OpenCSV and POJO?

How can I generate a CSV file from a POJO using OpenCSV while specifying both custom column headers and their positions?

public class MappingsBean {
    @CsvBindByName(column = "TradeID")
    @CsvBindByPosition(position = 0)
    private String tradeId;

    @CsvBindByName(column = "GWML GUID", required = true)
    @CsvBindByPosition(position = 1)
    private String gwmlGUID;

    // Additional fields...
}

Generating a CSV file in Java using OpenCSV can involve two aspects: custom column headers and specific column positions. By effectively leveraging annotations from OpenCSV, such as `@CsvBindByName` and `@CsvBindByPosition`, you can achieve this functionality seamlessly with your POJO (Plain Old Java Object). Here’s how to correctly implement this.

File reportFile = new File(reportOutputDir + "/" + REPORT_FILENAME);
Writer writer = new PrintWriter(reportFile);
StatefulBeanToCsv<MappingsBean> beanToCsv = new 
                                  StatefulBeanToCsvBuilder<MappingsBean>(writer)
                                      .withSeparator(',')
                                      .withEscapechar('"')
                                      .withOrderedResults(true)
                                      .build();
beanToCsv.write(makeFinalMappingBeanList());
writer.close();

// Use the additional functionality of OpenCSV to define headers:  
String[] headers = {"TradeID", "GWML GUID", "MXML GUID", "GWML File", "MxML File", "MxML Counterparty", "GWML Counterparty"};
// Write headers to the CSV before beans.

Causes

• The annotations `@CsvBindByPosition` and `@CsvBindByName` serve different purposes, which can lead to conflicts if not used correctly.
• The requirement to have both custom headers and specified positions may lead to challenges since certain OpenCSV functionalities are not designed to work together intuitively.

Solutions

• To use both annotations effectively, you can use `StatefulBeanToCsv` in conjunction with a custom `HeaderColumnNameMapping` to ensure that both custom headers and positions are retained in the generated CSV file.
• Make sure to include a configuration step where you define the header order explicitly or use a utility method to prepare your `List<MappingsBean>` accordingly.

Mistake: Omitting to define headers explicitly when combining both common annotations.

Solution: Always specify headers as a separate write step when using `StatefulBeanToCsv`.

Mistake: Not closing the writer properly which can lead to incomplete CSV files.

Solution: Ensure `writer.close()` is called within a finally block or use try-with-resources.