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Spring Batch 
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=> Spring Batch is a lightweight and powerful framework for processing large volumes of data.

=> It is robust framework designed for building batch processing applications in Java.

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What Is Batch Processing?
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Batch processing involves executing a series of automated jobs, it involves:

	1) Reading large amounts of data.

	2) Processing data in chunks.

	3) Writing the processed data somewhere (like a database, file, etc.).

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Batch Processing Real-time Usecases
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	- bulk msg
	- bulk email
	- processing file with millions of records
	- sending salaries for the emps (payroll systems)
	- sending bank acc stmt to acc holders
	- sending post paid bill reports
	- sending payment reminder notifications
	- Generating reports
	- Data migration between databases.

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Spring Batch Module Key Concepts
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	1) ItemReader

	2) ItemProcessor

	3) ItemWriter	

	4) Step

	5) JOB

	6) JobRepository

	7) JobLauncher

ItemReader : It is used to read data from the source 

ItemProcessor : It is used to process the data

ItemWriter : It is used to write the data to destination

Step : It represents sequence of our batch execution (reader + processor + writer)

Job : It is used to represents set of steps for batch processing

JobRepository : To maintains job execution history and steps info

JobLauncher: It is used to start the job exeuction.


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Batch Flow
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Request ==> RestController  ===> Job Launcher ==> Job ==> Step ==> (reader + processor + wrriter)

Note-1: Once job is executed we can csv file data inserted into DB table.

Note-2: Batch Execution details and Step execution details also we can find in DB tables.

// sql quries

show tables;

select * from people;

select * from batch_job_execution;

select * from batch_step_execution;

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Spring Batch Tutorial : https://youtu.be/2sdY-fKaR2o 

Spring Doc: https://spring.io/guides/gs/batch-processing

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