I have a Spring batch operation where I have sources file1, file2 and file3 to read from, and want to write to fileA, fileB and fileC like the following:
file1->fileA
file2->fileB
file3->fileC
When I look at an example for MultiResourceItemReader it implies that the [MultiResourceItemReader][2] is useful for combining operations - but not pipelining parallel operations. ie the usage pattern of MultiResourceItemReader is for appending:
file1->file2->file3->fileC
If I want to read a sequence of files as separate operations- is MultiResourceItemReader still the way to go?
You can use multiresourceparitioner, which is parallel and async, please refer spring batch sample programs here
MultiResourceItemReader:Reads items from multiple resources sequentially - resource list is given by setResources(Resource[]), the actual reading is delegated to setDelegate(ResourceAwareItemReaderItemStream). So the job of MultiResourceItemReader is correctly done. The problem is after delegating reading to the actual reader.
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I have written a spring batch program to read/process/write data into a single file. I have a new business requirement wherein from the same data what I am reading, I have to build another list with different data and process/format the data and write it onto a separate file.
I have looked into MultiFormatItemWriter in which I can define separate FlatFileItemWriters & CompositeItemWriter as well, but i am unable to understand how to send different lists to these different filewriters.
Please do suggest some options with sample code if possible.
A combination of ClassifierCompositeItemProcessor and ClassifierCompositeItemWriter is what you are looking for. The classifier allows you to route items to the right processor/writer based on their class.
You can find an example here.
I currently have a Spring Batch job that does the following:
Reads a list of csv files using a MultiResourceItemReader which delegates to a FlatFileItemReader.
Splits each file into chunks and writes each chunk as a JMS message, with each message containing the list of lines in the chunk and the filename of the underlying resource in JSON format.
What I want is for each chunk to only contain lines from a single file resource so that the filename on the JMS message will link up to the corresponding file.
The problem is that when processing of one file resource is complete, the reader will just continue and process the next resource meaning that lines from multiple resource files are being inserted into the same chunk and the filename property will not necessarily match the underlying data in the chunk.
Is there any clean way to prevent the reader from including lines from separate file resources in the same chunk?
EDIT: I believe the solution will require using a custom chunk completion policy to somehow determine if the current item being read is from the same resource as the previous line, not sure how feasible this is though. Any thoughts?.
I changed my implementation to use MultiResourcePartitioner to create a partitioned step per file, everything working now.
When processing a step level using chunk processing(specifying a commit-interval) in Spring Batch,is there a way to know inside the Writer,when all the records in a file have been read and processed.My idea was to pass the collection of records read from the file to the ExecutionContext once all the records have been read.
Please help.
I don't know if the is one of pre-built CompletionPolicy that do what you want, but if none you can write a custom CompletionPolicy that mark a chunk as completed when writer return null; in this way you hold all items read from file.
After that, are you sure this is exactly what you wnat? because store all item in ExecutionContext is not a good pratice; also you will lose chunk processing, restartability, and all other SB features...
I am using MultiResourceItemReader class of Spring Batch. Which uses FlatFileReader bean as delegate.My files contains XML requests, my batch reading requestes from files hit its on to URL and writing response to corresponding output files. I want to define one thread for each file processing to decrease execution time. In my current requirement I have four input files , I want to define four thread to read ,process and write files. I tried with simpleTaskExecuter with
task-executor="simpleTaskExecutor" throttle-limit="20"
But after using this flatfileReader is throwing Exception.
I am beginner, please suggest me how to implement this. Thanks in advance.
There are a couple ways to go here. However, the easiest way would be to partition by file using the MultiResourcePartitioner. That in combination with the TaskExecutorPartitionHandler will give you reliable parallel processing of your input files. You can read more about partitioning in section 7.4 of our documentation here: http://docs.spring.io/spring-batch/trunk/reference/html/scalability.html
Hi I am doing POC/base for design on reading database and writing into flat files. I am struggling on couple of issues here but first I will tell you the output format of flat file
Please let me know how do design the input writer where I need to read the transactions from different tables, process records , figure out the summary fields and then how should I design the Item Writer which has such a complex design. Please advice. I am successfully able to read from single table and write to file but the above task looks complex.
Extend the FlatFileItemWriter to only open a file once and append to it instead of overwriting it. Then pass that same filewriter into multiple readers in the order you would like them to appear. (Make sure that each object read by the readers are extensible by something that the writer understands! Maybe interface BatchWriteable would be a good name.)
Some back-of-the-envelope pseudocode:
Before everything starts:
Open file.
Write file headers.
Start Batch step
implement as many times as necessary
Read Batch section
Process Batch section
A Write Batch section
when done:
Write file footer
Close file