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Hunor Vadasz-Perhat
Hunor Vadasz-Perhat

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spring-002: setBeanName()-of-BeanNameAware-BeanFactory

#spring #java #programming

Here’s the detailed explanation of the execution flow with the actual code from a simple Java program to demonstrate BeanNameAware's setBeanName() lifecycle interface method.
Buckle up! It will be a long ride 🎢

1. Execution Starts in main()

  • The program begins execution in the main() method. The Spring context is initialized using the AnnotationConfigApplicationContext class with TenantConfig.class as its configuration.

Code:

 public static void main(String[] args) { // Initialize Spring context AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(TenantConfig.class); TenantService tenantService = context.getBean(TenantService.class); // Process tenant data tenantService.processTenantData(); }
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2. Spring Context Initialization

  • The AnnotationConfigApplicationContext processes the TenantConfig class annotated with @Configuration. It scans the package "org.example4" for components like @Service and other Spring-managed beans.

Code:

 @Configuration @ComponentScan(basePackages = "org.example4") // Adjust to your package structure public class TenantConfig { @Bean(name = "tenantA-dataSource") public TenantDataSource tenantADataSource() { return new TenantDataSource(); } @Bean(name = "tenantB-dataSource") public TenantDataSource tenantBDataSource() { return new TenantDataSource(); } }
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3. Bean Creation in TenantConfig

  • Spring invokes the two @Bean methods (tenantADataSource() and tenantBDataSource()) to create two beans of type TenantDataSource:
    • "tenantA-dataSource"
    • "tenantB-dataSource"

Code for @Bean definitions:

 @Bean(name = "tenantA-dataSource") public TenantDataSource tenantADataSource() { return new TenantDataSource(); } @Bean(name = "tenantB-dataSource") public TenantDataSource tenantBDataSource() { return new TenantDataSource(); }
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4. TenantDataSource Bean Initialization

  • The TenantDataSource class implements BeanNameAware, allowing the Spring container to call the setBeanName(String beanName) method during bean initialization.
  • The setBeanName method extracts the tenant name (tenantA or tenantB) from the bean name and assigns a corresponding database URL.

Code:

 public class TenantDataSource implements BeanNameAware { private String tenantName; private String databaseUrl; @Override public void setBeanName(String beanName) { // Extract tenant name from the bean name if (beanName.contains("-")) { this.tenantName = beanName.split("-")[0]; } else { throw new IllegalArgumentException("Invalid bean naming convention. Expected format: <tenantName>-dataSource"); } // Assign a database URL dynamically based on the tenant name this.databaseUrl = "jdbc:mysql://localhost:3306/" + tenantName + "_db"; } public void connect() { System.out.println("Connecting to database for tenant: " + tenantName); System.out.println("Using database URL: " + databaseUrl); // Simulate connection logic here } }
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5. TenantService Bean Creation

  • Spring scans the package "org.example4" and finds the TenantService class annotated with @Service.
  • The TenantService constructor has dependencies annotated with @Qualifier, which specifies which TenantDataSource beans to inject:
    • "tenantA-dataSource"
    • "tenantB-dataSource"

Code:

 @Service public class TenantService { private final TenantDataSource tenantADataSource; private final TenantDataSource tenantBDataSource; @Autowired public TenantService( @Qualifier("tenantA-dataSource") TenantDataSource tenantADataSource, @Qualifier("tenantB-dataSource") TenantDataSource tenantBDataSource ) { this.tenantADataSource = tenantADataSource; this.tenantBDataSource = tenantBDataSource; } public void processTenantData() { System.out.println("Processing data for all tenants..."); tenantADataSource.connect(); tenantBDataSource.connect(); } }
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6. Retrieving TenantService from Context

  • Back in the main() method, the TenantService bean is retrieved from the Spring context:

     TenantService tenantService = context.getBean(TenantService.class);

  • This bean is fully initialized, with its dependencies injected.

7. Calling processTenantData()

  • The processTenantData() method is invoked on the TenantService bean.
  • Inside the method:
    • A message is printed: "Processing data for all tenants...".
    • The connect() method is called on both tenantADataSource and tenantBDataSource.

Code in main():

 tenantService.processTenantData();
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Code in TenantService:

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

  • For each TenantDataSource bean, the connect() method:

    • Prints the tenantName and databaseUrl: 
     Connecting to database for tenant: tenantA Using database URL: jdbc:mysql://localhost:3306/tenantA_db Connecting to database for tenant: tenantB Using database URL: jdbc:mysql://localhost:3306/tenantB_db

Code in TenantDataSource:

 public void connect() { System.out.println("Connecting to database for tenant: " + tenantName); System.out.println("Using database URL: " + databaseUrl); // Simulate connection logic here }
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9. Program Completion

  • After processing data for both tenants, the program completes execution.

Complete Output: 

Processing data for all tenants... Connecting to database for tenant: tenantA Using database URL: jdbc:mysql://localhost:3306/tenantA_db Connecting to database for tenant: tenantB Using database URL: jdbc:mysql://localhost:3306/tenantB_db
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More info at https://docs.spring.io/spring-framework/docs/6.2.2/javadoc-api/org/springframework/beans/factory/BeanFactory.html

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