spring-: setBeanName()-of-BeanNameAware-BeanFactory

This detailed walkthrough illustrates the BeanNameAware interface's setBeanName() method within a simple Java Spring application. Let's explore the execution flow step-by-step.

1. Program Execution Begins (main())

The program starts in the main() method. A Spring context is initialized using AnnotationConfigApplicationContext, loading configuration from TenantConfig.class. The TenantService bean is then retrieved.

public static void main(String[] args) {
    AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(TenantConfig.class);
    TenantService tenantService = context.getBean(TenantService.class);
    tenantService.processTenantData();
}

2. Spring Context Initialization

AnnotationConfigApplicationContext processes the @Configuration-annotated TenantConfig class. It scans the specified package (adjust basePackages as needed) for Spring-managed beans (@Service, etc.).

@Configuration
@ComponentScan(basePackages = "org.example4")
public class TenantConfig {
    @Bean(name = "tenantA-dataSource")
    public TenantDataSource tenantADataSource() { return new TenantDataSource(); }

    @Bean(name = "tenantB-dataSource")
    public TenantDataSource tenantBDataSource() { return new TenantDataSource(); }
}

3. Bean Creation (TenantConfig)

Spring calls the @Bean methods (tenantADataSource() and tenantBDataSource()) to create two TenantDataSource beans: "tenantA-dataSource" and "tenantB-dataSource".

4. TenantDataSource Initialization

TenantDataSource implements BeanNameAware. During bean initialization, Spring calls setBeanName(String beanName). This method extracts the tenant name ("tenantA" or "tenantB") from the bean name and sets the database URL accordingly.

public class TenantDataSource implements BeanNameAware {
    private String tenantName;
    private String databaseUrl;

    @Override
    public void setBeanName(String beanName) {
        this.tenantName = beanName.split("-")[0];
        this.databaseUrl = "jdbc:mysql://localhost:3306/" + tenantName + "_db";
    }

    public void connect() {
        System.out.println("Connecting to database for tenant: " + tenantName);
        System.out.println("Database URL: " + databaseUrl);
    }
}

5. TenantService Bean Creation

Spring finds TenantService (@Service). The constructor uses @Qualifier to specify which TenantDataSource beans to inject.

@Service
public class TenantService {
    private final TenantDataSource tenantADataSource;
    private final TenantDataSource tenantBDataSource;

    @Autowired
    public TenantService(@Qualifier("tenantA-dataSource") TenantDataSource tenantA,
                         @Qualifier("tenantB-dataSource") TenantDataSource tenantB) {
        this.tenantADataSource = tenantA;
        this.tenantBDataSource = tenantB;
    }

    public void processTenantData() {
        System.out.println("Processing data for all tenants...");
        tenantADataSource.connect();
        tenantBDataSource.connect();
    }
}

6. Retrieving TenantService

In main(), TenantService is retrieved from the context (context.getBean(TenantService.class)). It's fully initialized with its dependencies.

7. Calling processTenantData()

tenantService.processTenantData() is called.

8. Database Connection

tenantADataSource.connect() and tenantBDataSource.connect() are called, printing connection details.

9. Program Termination

The program finishes after processing tenant data.

Complete Console Output:

<code>Processing data for all tenants...
Connecting to database for tenant: tenantA
Database URL: jdbc:mysql://localhost:3306/tenantA_db
Connecting to database for tenant: tenantB
Database URL: jdbc:mysql://localhost:3306/tenantB_db</code>

For more details on BeanFactory, refer to the Spring Framework documentation. This example showcases how BeanNameAware allows beans to be aware of their assigned names within the Spring container, enabling dynamic configuration based on these names.

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