OpenCSV - How to map selected columns to Java Bean regardless of order?

Question

I have a CSV file with the following columns: id, fname, telephone, lname, address.

I have a P

Answer 1

Use @CsvIgnore annotation above the field which need not to be written to csv file.

Answer 2

Recent versions of OpenCSV deprecate the method parse(X, Y) and it's recommenced to use BeanBuilder instead, so the top answer is out of date.

try {
    CsvToBeanBuilder<PersonCSV> beanBuilder = new CsvToBeanBuilder<>(new InputStreamReader(new FileInputStream("your.csv")));

    beanBuilder.withType(PersonCSV.class);
    // build methods returns a list of Beans
    beanBuilder.build().parse().forEach(e -> log.error(e.toString()));

} catch (FileNotFoundException e) {
    log.error(e.getMessage(), e);
}

This methods allows you to clean up the code and remove MappingStrategy (you can still use it if you like spaghetti), so you can annotate your CSV class as follows:

@CsvDate("dd/MM/yyyy hh:mm:ss")
@CsvBindByName(column = "Time Born", required = true)
private Date birthDate;

Answer 3

SimpleFlatMapper can do that easily see Getting Started csv using the headers of the csv or by manually specifying which columns map to what property.

CsvParser
    .mapTo(MyObject.class)
    .forEach(file, System.out::println);

Answer 4

With opencsv, you can create a generic function like :

public static <T> void csvWriterUtil(Class<T> beanClass, List<T> data, String outputFile, String[] columMapping){
    try{
        Writer writer = new BufferedWriter(new FileWriter(outputFile));
        ColumnPositionMappingStrategy<T> strategy = new ColumnPositionMappingStrategy<>();
        strategy.setType(beanClass);
        strategy.setColumnMapping(columMapping);
        StatefulBeanToCsv<T> statefulBeanToCsv =new StatefulBeanToCsvBuilder<T>(writer)
                .withMappingStrategy(strategy)
                .build();
        writer.write(String.join(",",columMapping)+"\n");
        statefulBeanToCsv.write(data);
        writer.close();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (CsvRequiredFieldEmptyException e) {
        e.printStackTrace();
    } catch (CsvDataTypeMismatchException e) {
        e.printStackTrace();
    }
}

Here you can pass only required columns through columMapping parameter. Code example is available in https://github.com/soumya-kole/JavaUtils/tree/master/CsvUtil

Answer 5

Here is a nice way to do use OpenCSV to do the mapping to POJO generically:

protected <T> List<T> mapToCSV(String csvContent, Class<T> mapToClass) {
    CsvToBean<T> csvToBean = new CsvToBean<T>();

    Map<String, String> columnMapping = new HashMap<>();
    Arrays.stream(mapToClass.getDeclaredFields()).forEach(field -> {
        columnMapping.put(field.getName(), field.getName()); 
    });

    HeaderColumnNameTranslateMappingStrategy<T> strategy = new HeaderColumnNameTranslateMappingStrategy<T>();
    strategy.setType(mapToClass);
    strategy.setColumnMapping(columnMapping);

    CSVReader reader = new CSVReader(new StringReader(csvContent));
    return csvToBean.parse(strategy, reader);
}


public static class MyPojo {
    private String foo, bar;

    public void setFoo(String foo) {
        this.foo = foo;
    }

    public void setBar(String bar) {
        this.bar = bar;
    }
}

Then from your test you can use:

List<MyPojo> list = mapToCSV(csvContent, MyPojo.class);

Answer 6

Have a look at jcsvdao, https://github.com/eric-mckinley/jcsvdao/ , uses hibernate style mapping files and can handle 1to1 and 1toMany relations. Good if you dont own the csv files as has flexible matching strategies.