#Bean works without #Configuration. How can it still work without #Configuration? - spring

Question

The bottom code is my Spring Batch program code. when you see the bottom, you can see the code's problem. there is no #Configuration. originally, it was impossible to inject to dependency classes, but it was injected.
The first image is my project explorer.
I will inject dataSource to dataSource in BatchJob but it can't work because I didn't add #Configuration at BatchConfiguration. class but it still work even no #Configuration. so I wonder How can#Bean DataSource inject without #Configuration? you can check second image what this project works.
so plz I wanna solve my wondering and you can see that full source in my github address and my English skill is not good
package com.bootbatch.job;
import org.springframework.batch.core.configuration.annotation.EnableBatchProcessing;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.core.io.ClassPathResource;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.jdbc.datasource.init.DataSourceInitializer;
import org.springframework.jdbc.datasource.init.ResourceDatabasePopulator;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import javax.sql.DataSource;
#ComponentScan("com.bootbatch")
#PropertySource("classpath:/database.properties")
#EnableBatchProcessing
public class BatchConfiguration {
#Autowired
private Environment env;
#Bean
public DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setUrl(env.getRequiredProperty("jdbc.url"));
dataSource.setUsername(env.getProperty("jdbc.username"));
dataSource.setPassword(env.getProperty("jdbc.password"));
return dataSource;
}
#Bean
public DataSourceInitializer databasePopulator() {
System.out.println("===>databasePopulator에 접속!!");
ResourceDatabasePopulator populator = new ResourceDatabasePopulator();
populator.addScript(new ClassPathResource("org/springframework/batch/core/schema-oracle10g.sql"));
// populator.addScript(new ClassPathResource("truncate_secondjob.sql"));
populator.setContinueOnError(true);
populator.setIgnoreFailedDrops(true);
DataSourceInitializer initializer = new DataSourceInitializer();
initializer.setDatabasePopulator(populator);
initializer.setDataSource(dataSource());
return initializer;
}
}

Answer 1

The "problem" is your own code in your main method (which you hapilly forgot to include in your question!).
#SpringBootApplication
public class SpringBootBatch06Application {
public static void main(String[] args) throws JobExecutionAlreadyRunningException, JobRestartException, JobInstanceAlreadyCompleteException, JobParametersInvalidException, InterruptedException {
SpringApplication.run(SpringBootBatch06Application.class, args);
ApplicationContext context = new AnnotationConfigApplicationContext(BatchConfiguration.class, BatchJob.class);
// Other code removed
}
}
You are creating a new AnnotationConfigApplicationContext for those 2 classes. Which will make those 2 classes components automatically (regardless of a #Component or #Configuration annotation). So you are basically working around Spring Boot and its auto-configuration (probably because it didn't work).
It is also allowed for #Components to have #Bean methods, they will operate in so called "lite #Bean Mode" (see this section of the Spring Reference Guide).
So because they are now first of all components (or beans) and have #Bean methods they will produce new beans (although not as you think they do, read the aformentioned documentation).