Reading Records From a Database in Spring Batch - spring-batch

Question

I'm trying to read some records from a database using loops then do some calculations on the records (updating a field called total).
But i'm new to spring batch so please can anyone provide me with some tips.

Answer 1

this sounds like something the chunk pattern would address. you can use re-use existing Spring Batch components to read from the database, compose your own processor, then pass back to a Spring Batch component to store.
say the use case is like this;
- read a record
- record.setTotalColumn(record.getColumn2() + record.getColumn3())
- update
this configuration might look like this
<batch:job id="recordProcessor">
<batch:step id="recordProcessor.step1">
<batch:tasklet>
<batch:chunk reader="jdbcReader" processor="calculator" writer="jdbcWriter" commit-interval="10"/>
</batch:tasklet>
</batch:step>
</batch:job>
<bean id="jdbcReader" class="org.springframework.batch.item.database.JdbcCursorItemReader">
<property name="dataSource" ref="dataSource"/>
<property name="sql" value="select idColumn,column1,column2,totalColumn from my_table"/>
<property name="rowMapper" ref="myRowMapper"/>
</bean>
<bean id="jdbcWriter" class="org.springframework.batch.item.database.JdbcBatchItemWriter">
<property name="dataSource" ref="dataSource"/>
<property name="sql" value="update my_table set totalColumn = :value where idColumn = :id"/>
</bean>
<bean id="calculator" class="de.incompleteco.spring.batch.step.item.CalculationProcessor"/>
this means that the only thing you have to 'write' from scratch would be the calculator processor which could e something like this;
package de.incompleteco.spring.batch.step.item;
import org.springframework.batch.item.ItemProcessor;
public class CalculationProcessor implements ItemProcessor<MyObject, MyObject> {
#Override
public MyObject process(MyObject item) throws Exception {
//do the math
item.setTotalColumn(item.getColumn1() + item.getColumn2());
//return
return item;
}
}