I trying to write a spring batch using SpringBoot. At first the program will read data from database, then write it to .csv file format.

This is the code I have tried

Reader

     @Bean
        public ItemReader<A> Reader() throws Exception {
            List list = new ArrayList<>();
            JdbcCursorItemReader<A> reader = new JdbcCursorItemReader<A>();
            JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);

            String sql = "SELECT ID AS id FROM TABLE_A ";
            list = jdbcTemplate.query(sql, new Mapper()); // store all retrieved data to list
            reader.setSql(sql);
            reader.setDataSource(dataSource);
            reader.setRowMapper(new Mapper());

            if (list != null) {
                for (A c : (List<A>) list) {
                    c.setId("123");  // overwrite the id
                    c.setState("Active");             
                }
            }
            return reader;
        }

Mapper

           public class Mapper implements RowMapper<A> {

                @Override
                public A mapRow(ResultSet rs, int rowNum) throws SQLException {

                    A c = new A();
                    c.setId(rs.getString("id"));

        }

Writer

    @Bean
        public ItemWriter<A> Writer() {
            FlatFileItemWriter<A> csvFileWriter = new FlatFileItemWriter<>();
            String exportFileHeader = "ID" + delimiter + "State";
            StringHeaderWriter headerWriter = new StringHeaderWriter(exportFileHeader);
            csvFileWriter.setHeaderCallback(headerWriter);
            headerWriter.checkRepository();

            String exportFilePath = "/home/xxx/Desktop/outputs/" + fileName + time() + ".csv";
            csvFileWriter.setResource(new FileSystemResource(exportFilePath));
            LineAggregator<A> lineAggregator = createStudentLineAggregator();
            csvFileWriter.setLineAggregator(lineAggregator);
            return csvFileWriter;
        }

When I check the generated file, I can see the value id from database, but not 123. Value for the State is also empty . How can I overwrite the mapping value ?

To solve this, I need to move the data that need to be inserted to Processor.

 public class Processor implements ItemProcessor<A, A> {
            @Override
            public A process(A i) throws Exception {
                System.out.println("Processing..." + i);
                i.setId("123");
                i.setStatus("Active");
                return i;
            }       
     }