Java Reference
In-Depth Information
Listing 9-6.
Output Configuration for Format Job
…
<beans:bean id="outputFile"
class="org.springframework.core.io.FileSystemResource" scope="step">
<beans:constructor-arg value="#{jobParameters[outputFile]}"/>
</beans:bean>
<beans:bean id="flatFileOutputWriter"
class="org.springframework.batch.item.file.FlatFileItemWriter">
<beans:property name="resource" ref="outputFile"/>
<beans:property name="lineAggregator" ref="formattedLineAggregator"/>
</beans:bean>
<beans:bean id="formattedLineAggregator"
class="org.springframework.batch.item.file.transform.
FormatterLineAggregator">
<beans:property name="fieldExtractor">
<beans:bean class="org.springframework.batch.item.file.transform.
BeanWrapperFieldExtractor">
<beans:property name="names"
value="firstName,lastName,address,city,state,zip"/>
</beans:bean>
</beans:property>
<beans:property name="format" value="%s %s lives at %s %s in %s, %s."/>
</beans:bean>
…
As Listing 9-6 shows, the configuration for the output side of this step is actually smaller than the
input. You begin by configuring of the output file; again, the name of the file is passed in as a job
parameter. Next you have the configuration of the
FlatFileItemWriter
.
flatFileOutputWriter
takes two
dependencies: a resource (the file to write to) and the
LineAggregator
implementation. The last piece of
the output puzzle is the
LineAggregator
implementation:
FormatterLineAggregator
in this case. It takes
two dependencies: a
FieldExtractor
implementation and a format.
The
org.springframework.batch.item.file.transform.FieldExtractor
interface is intended to
abstract the process of taking the fields of an object tree and convert them into an
Object
array. With the
objects to be written into an array, the
FormatterLineAggregator
uses Java's
String.format()
method in
conjunction with the string provided in the format dependency to generate the formatted
String
to be
written to the file. In this case,
BeanWrapperFieldExtractor
uses the getters for each of the properties
defined and returns the results, in order, in an
Object
array to be formatted according to the format
string. In the case of Listing 9-6, you're extracting the
firstName
,
lastName
,
address
,
city
,
state
, and
zip
from each item. It's important to note that there is no key/value pairing during the formatting process. If
you want a bean property to appear twice in the formatted
String
, you need to include it twice, in order,
in the names list.
With all of the input and output configured, all you need to do to complete the job is configure the
step and job. Listing 9-7 shows the complete configuration of
formatJob
including the previous input
and output.
