How to write this method in a generic way in java

Question

Currently, I have this method implemented for five different class to configure FlatFileReader for five different text files and load into DB table.

I would like to know is there a way to implement this method in a common place So that my each file will call this method to configure my reader to read their corresponding files..

Every file will send different entity class to load their file. like Primary Entity, ChildEntity1, ChildEntity2, ChildEntity3, ChildEntity4.

private void flatFileItemReaderConfig(FlatFileItemReader<PrimaryEntity> flatFileReader,
        String fileName, String incomingHeader)
{
    // set delimiter as '|'
    DefaultLineMapper<PrimaryEntity> defaultLineMapper = new DefaultLineMapper<>();

    DelimitedLineTokenizer delimitedLineTokenizer = new DelimitedLineTokenizer("|");
    delimitedLineTokenizer.setNames(convertHeaderToEntityAttrib(fileName, incomingHeader));
    defaultLineMapper.setLineTokenizer(delimitedLineTokenizer);

    // convert each record into primaryentity
    BeanWrapperFieldSetMapper<PrimaryEntity> beanWrapperFieldSetMapper = new BeanWrapperFieldSetMapper<>();
    beanWrapperFieldSetMapper.setTargetType(PrimaryEntity.class);
    beanWrapperFieldSetMapper.setCustomEditors(getCustomFormatters());

    defaultLineMapper.setFieldSetMapper(beanWrapperFieldSetMapper);

    flatFileReader.setLineMapper(defaultLineMapper);
}

Which classes have the shared functionality? is this method the one that is duplicated? — cameron1024, Aug 13 '19 at 10:31
@cameron1024 yes this method only...FlatFileItemReader> it will have different entity class as i mentioned in the question.. — Saravanan, Aug 13 '19 at 10:33
This already seems to be generic. If you replace `FlatFileItemReader` with `FlatFileItemReader`, do you get errors? If so, what are those errors. — cameron1024, Aug 13 '19 at 10:35

score 4 · Accepted Answer · edited Dec 14 '20 at 17:12

Add generics to the method

private <T> void flatFileItemReaderConfig(FlatFileItemReader<T> flatFileReader, String fileName, String incomingHeader, Class<T> clazz) {

    // set delimiter as '|'
    DefaultLineMapper<T> defaultLineMapper = new DefaultLineMapper<>();

    DelimitedLineTokenizer delimitedLineTokenizer = new DelimitedLineTokenizer("|");
    delimitedLineTokenizer.setNames(convertHeaderToEntityAttrib(fileName, incomingHeader));
    defaultLineMapper.setLineTokenizer(delimitedLineTokenizer);

    // convert each record into primary entity
    BeanWrapperFieldSetMapper<T> beanWrapperFieldSetMapper = new BeanWrapperFieldSetMapper<>();
    beanWrapperFieldSetMapper.setTargetType(clazz);
    beanWrapperFieldSetMapper.setCustomEditors(getCustomFormatters());
    defaultLineMapper.setFieldSetMapper(beanWrapperFieldSetMapper);
    flatFileReader.setLineMapper(defaultLineMapper);
}

If you want to limit the usage only to the listed entities, create a common interface Entity that is implemented by all concrete entities (PrimaryEntity, ChildEntity1, ChildEntity2, ChildEntity3, ChildEntity4) and change the signature to

private <T extends Entity> void flatFileItemReaderConfig(...)

I'd avoid making the method static because it complicates testing. — Jardo, Aug 13 '19 at 15:29
@Jardo removing my comment about static since it's irrelevant for the question. — Eyal, Aug 13 '19 at 15:39

How to write this method in a generic way in java

1 Answers1