[Spring Batch][Mongo] Cannot read jobParameters in ItemReader read() - mongodb

Question

I have set a step configuration and ItemReader to read data from mongoDB in same file like this...
#Bean("STEP_FETCH_DATA")
public Step fetchDatabaseStep(
ItemReader<ExampleDao> dataReader,
DataProcessor dataProcessor,
DataWriter dataWriter,
#Qualifier("TASK_EXECUTOR") TaskExecutor taskExecutor
) {
log.info("Initialize step: {}", "STEP_FETCH_DATA");
return stepBuilderFactory.get("STEP_FETCH_DATA")
.<ExampleDao, ExampleDao>chunk(chunkSize)
.processor(dataProcessor)
.reader(dataReader)
.writer(dataWriter)
.taskExecutor(taskExecutor)
.build();
}
#Bean("dataReader")
#StepScope
public ItemReader<ExampleDao> read(#Value("#{jobParameters.get(\"batchRunDate\")}") String batchRunDate) throws UnexpectedInputException, ParseException, NonTransientResourceException {
log.info("Reading start... batchRunDate : {}", batchRunDate);
MongoItemReader<ExampleDao> reader = new MongoItemReader<>();
reader.setTemplate(mongoTemplate);
reader.setSort(new HashMap<String, Sort.Direction>() {{
put("_id", Sort.Direction.DESC);
}});
reader.setTargetType(ExampleDao.class);
reader.setQuery("{}");
return reader;
}
From above code, it can access my jobParameter and working as expected.
However, if I create a class to contain my mongo ItemReader like this
#Component
#Slf4j
public class DataReaderExample {
#Autowired
private MongoTemplate mongoTemplate;
#Bean
#StepScope
public ItemReader<ExampleDao> read(#Value("#{jobParameters.get(\"batchRunDate\")}") String
batchRunDate) throws UnexpectedInputException, ParseException, NonTransientResourceException {
log.info("Reading start... batchRunDate : {}", batchRunDate);
MongoItemReader<ExampleDao> reader = new MongoItemReader<>();
reader.setTemplate(mongoTemplate);
reader.setSort(new HashMap<String, Sort.Direction>() {{
put("_id", Sort.Direction.DESC);
}});
reader.setTargetType(ExampleDao.class);
reader.setQuery("{}");
return reader;
}
}
Then set a step configuration like this. (Notice the .reader(dataReadExample.read(null)). I expected #Value("#{jobParameters.get("batchRunDate") in read() argument will overide the null value)
#Bean("STEP_FETCH_DATA")
public Step fetchDatabaseStep(
DataReaderExample dataReadExample ,
DataProcessor dataProcessor,
DataWriter dataWriter,
#Qualifier("TASK_EXECUTOR") TaskExecutor taskExecutor
) {
log.info("Initialize step: {}", "STEP_FETCH_DATA");
return stepBuilderFactory.get("STEP_FETCH_DATA")
.<ExampleDao, ExampleDao>chunk(chunkSize)
.processor(dataProcessor)
.reader(dataReadExample.read(null))
.writer(dataWriter)
.taskExecutor(taskExecutor)
.build();
}
My log.info("Reading start... batchRunDate : {}", batchRunDate); the batch will always print out as null value and the #Value("#{jobParameters.get("batchRunDate") is not working. Seem like I cannot access the jobParameters.
Have anyone could explain me about this behavior and how to move the ItemReader to another class. My goal is to seperate ItemReader into another class. Thanks!

Answer 1

Your DataReaderExample is declared as a #Component, it should rather be a #Configuration class in which you declare bean definitions.
I suggest to change the read method to itemReader or something similar because its purpose is to define the item reader bean and not actually read the data.
Once that done, you can import your DataReaderExample configuration class in your application context and autowire the item reader in your step:
#Bean("STEP_FETCH_DATA")
public Step fetchDatabaseStep(
ItemReader<ExampleDao> itemReader ,
DataProcessor dataProcessor,
DataWriter dataWriter,
#Qualifier("TASK_EXECUTOR") TaskExecutor taskExecutor
) {
log.info("Initialize step: {}", "STEP_FETCH_DATA");
return stepBuilderFactory.get("STEP_FETCH_DATA")
.<ExampleDao, ExampleDao>chunk(chunkSize)
.processor(dataProcessor)
.reader(itemReader)
.writer(dataWriter)
.taskExecutor(taskExecutor)
.build();
}