Usage of CustomEditor with BeanWrapperFieldExtractor just like with BeanWrapperFieldSetMapper - spring-batch

Question

I have written a simple Spring Batch application that reads a CSV file, does some transforming and writes a modified CSV to the disk.
The reading of the file into domain objects works like a charm. I use DelimitedLineTokenizer to tokenize the lines and a BeanWrapperFieldSetMapper to feed the values into a bean:
<bean id="reader" class="org.springframework.batch.item.file.FlatFileItemReader" scope="step">
<property name="resource" value="#{jobParameters['inputResource']}" />
<property name="linesToSkip" value="1" />
<property name="lineMapper">
<bean class="org.springframework.batch.item.file.mapping.DefaultLineMapper">
<property name="lineTokenizer">
<bean class="org.springframework.batch.item.file.transform.DelimitedLineTokenizer">
<property name="delimiter" value=";" />
<property name="names"
value="ID,NAME,DESCRIPTION,PRICE,DATE" />
</bean>
</property>
<property name="fieldSetMapper">
<bean class="org.springframework.batch.item.file.mapping.BeanWrapperFieldSetMapper">
<property name="targetType" value="myapp.MyDomainObject" />
<property name="customEditors">
<map>
<entry key="java.util.Date" value-ref="dateEditor" />
<entry key="java.math.BigDecimal" value-ref="numberEditor" />
</map>
</property>
</bean>
</property>
</bean>
</property>
</bean>
I especially like the features of BeanWrapperFieldSetMapper to "guess" the field names and the possibility to define CustomEditors which I use to define the special date and number formats used in the input file.
Now I would like to write the modified file in the same format like the input file.
I use the following configuration:
<bean id="writer" class="org.springframework.batch.item.file.FlatFileItemWriter" scope="step">
<property name="resource" value="#{jobParameters['outputResource']}" />
<property name="lineAggregator">
<bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator">
<property name="delimiter" value=";" />
<property name="fieldExtractor">
<bean class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor">
<property name="names" value="id,name,description,price,date" />
</bean>
</property>
</bean>
</property>
</bean>
There are two things I miss with this configuration:
BeanWrapperFieldSetMapper allowed me to set CustomEditors, but BeanWrapperFieldExtractor has no such possibility. Is there a way to use these?
Is there a way to define the headings in the first line of the file? I have not found any way to write an initial line that is not a bean... It would be great to use the same names here as in BeanWrapperFieldSetMapper such that BeanWrapperFieldExtractor writes the inital line and guesses the bean property namens as BeanWrapperFieldSetMapper does.
The process to load files is so comfortable in Spring Batch. Why is the writing of files so different? Am I missing something?
I have to use Spring Batch 2.1.x because we are using Spring 3.0.x . Therefor an upgrade to 2.2.x would not be an option.

Answer 1

Which is your need? Extract field property as text? You can
use a FormatterLineAggregator if you needs are not too complicated
write your own CustomEditorsFieldExtractor (better)
Generate a complex domain object composed by original domain object and by text-formatted object and use last one as parameter of writer (but breaks your current processor/writer)
Use FlatFileItemWriter.headerCallback: if setted allow custom header write
Writing - in your case - seems a pain respect read process because spring-batch's reading components fits your needs. Standard components fits more used use-case and they cover a lot of scenario. Let us write a custom FieldExtractor sometimes! :)