ItemReader Code repetition problem in spring batch

Question

Suppose I have two classes implemented in the following manner (Ommiting job and chunk code for the sake of clarity). Each reader will have a delimiter based on the configuration class they are declared.

1) There is clearly code repetition that I would love to generalize in another class, because if I decide to add code in class*ItemReader(), I would have to do it across several files. How can that be accomplished? Not only the "delimiter" is important here, but the class inside <> in the itemReaderBuilder

2) How can I avoid having different names for each of the methods? the are basically the same, they just need a different class inside <> and a different delimiter.

3) How can I avoid the need to save the reader inside the configuration class to calculate the resource path in runtime (using a tasklet) as is date based.

@Configuration
public ClassA{

    @Value("${fileA.delimiter}")
    private String delimiter;

    private ItemReader reader;

    @Bean
    public ItemReader classAItemReader(){

            reader =  FlatFileItemReaderBuilder<ObjectA>
                .get("reader")
                .delimiter(this.delimiter)                
                .blabla()
                .build()

            return reader
    }
}

@Configuration
public ClassB{

    @Value("${fileB.delimiter}")
    private String delimiter;

    private ItemReader reader;

    @Bean
    public ItemReader classBItemReader(){

            reader =  FlatFileItemReaderBuilder<ObjectA>
                .get("reader")
                .delimiter(this.delimiter)                
                .blabla()
                .build()

            return reader
    }
}

Answer 1

One option I see for your use case is to define an abstract generic configuration class in which you define a generic reader. Here is an example:

import org.springframework.batch.item.ItemReader;
import org.springframework.batch.item.file.builder.FlatFileItemReaderBuilder;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;

public abstract class MyReaderConfiguration<T> {

    @Value("${file.delimiter}")
    private String delimiter;

    @Value("${file.columns}") // column1,column2
    private String fields;

    @Bean
    public ItemReader<T> itemReader(){
        return new FlatFileItemReaderBuilder<T>()
                .name("reader")
                .delimited()
                .delimiter(delimiter)
                .names(fields.split(","))
                .build();
    }

}

Other parts of your job definition can go in a subclass with the desired target type (ObjectA or ObjectB).