I need to add the aliases defined in the SQL query while generating the CSV file.
I see some example using FlatFileHeaderCallback but there I don't have a way to pass the aliases
is there any way to get the column aliases in write(List<? extends T> items) method of FlatFileItemWriter
For starters, I think you could simply use a custom FlatFileHeaderCallback which takes a String as a parameter and writes it :
public class CustomHeaderWriter implements FlatFileHeaderCallback {
private String header;
@Override
public void writeHeader(Writer writer) throws IOException {
writer.write(header);
}
public void setHeader(String header) {
this.header = header;
}
}
To use it, declare it in your FlatFileItemWriter and give it a String that contains the name of your columns/aliases separated by your flat file delimiter :
<bean class="org.springframework.batch.item.file.FlatFileItemWriter" scope="step">
<property name="headerCallback">
<bean class="xx.xx.xx.CustomHeaderWriter">
<property name="header" value="${columns.or.aliases}"></property>
</bean>
</property>
</bean>
Now, I suppose you don't want to write the columns/aliases a second time for the header, and would like to "extract" them from the SQL query. This could be accomplished for example by fiddling with the CustomHeaderWriter :
SELECT and FROM, split with ,, strip quotes, etc.)FlatFileItemWriter
Create a custom class(assuming 5 csv columns):
public class MyFlatFileWriter implements FlatFileHeaderCallback {
@Override
public void writeHeader(Writer writer) throws IOException {
writer.write("Col1,Col2,Col3,Col4,Col5");
}
}
Add bean & its reference in writer bean:
<bean id="flatFileWriter" class="org.springframework.batch.item.file.FlatFileItemWriter">
<property name="resource" value="file:csv/outputs/name.csv" />
<property name="headerCallback" ref="headerCallback" />
<property name="lineAggregator">
............
</property>
</bean>
<bean id="headerCallback" class="com.whatever.model.MyFlatFileWriter" />
