Spring Batch : PassThroughFieldExtractor with BigDecimal formatting - spring-batch

Question

I'm using Spring Batch to extract a CSV file from a DB table which has a mix of column types. The sample table SQL schema is
[product] [varchar](16) NOT NULL,
[version] [varchar](16) NOT NULL,
[life_1_dob] [date] NOT NULL,
[first_itm_ratio] [decimal](9,6) NOT NULL,
the sample Database column value for the 'first_itm_ration' field are
first_itm_ratio
1.050750
0.920000
but I would like my CSV to drop the trailing zero's from values.
first_itm_ratio
1.05075
0.92
I'd prefer not to have to define the formatting for each specific field in the table, but rather have a global object specific formatting for all columns of that data type.
My csvFileWriter bean
<bean id="csvFileWriter" class="org.springframework.batch.item.file.FlatFileItemWriter" scope="step">
<property name="resource" ref="fileResource"/>
<property name="lineAggregator">
<bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
<property name="delimiter">
<util:constant static-field="org.springframework.batch.item.file.transform.DelimitedLineTokenizer.DELIMITER_COMMA"/>
</property>
<property name="fieldExtractor">
<bean class="org.springframework.batch.item.file.transform.PassThroughFieldExtractor" />
</property>
</bean>
</property>
</bean>

Answer 1

You can
Write your own BigDecimalToStringConverter implements Converter<BigDecimal, String> to format big decimal without trailing 0's
Create a new ConversionService (MyConversionService) and register into the custom converter
Extends DelimitedLineAggregator, inject MyConversionService, override doAggregate() to format fields using injected conversion service
public class MyConversionService extends DefaultConversionService {
public MyConversionService() {
super();
addConverter(new BigDecimalToStringConverter());
}
}
public class MyFieldLineAggregator<T> extends DelimitedLineAggregator<T> {
private ConversionService cs = new MyConversionService();
public String doAggregate(Object[] fields) {
for(int i = 0;i < fields.length;i++) {
final Object o = fields[i];
if(cs.canConvert(o.getClass(), String.class)) {
fields[i] = cs.convert(o, String.class);
}
}
return super.doAggregate(fields);
}
}