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

0416

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: 

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

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

       <span>@Bean</span><span>(</span><span>name</span> <span>=</span> <span>"tenantA-dataSource"</span><span>)</span>
       <span>public</span> <span>TenantDataSource</span> <span>tenantADataSource</span><span>()</span> <span>{</span>
           <span>return</span> <span>new</span> <span>TenantDataSource</span><span>();</span>
       <span>}</span>

       <span>@Bean</span><span>(</span><span>name</span> <span>=</span> <span>"tenantB-dataSource"</span><span>)</span>
       <span>public</span> <span>TenantDataSource</span> <span>tenantBDataSource</span><span>()</span> <span>{</span>
           <span>return</span> <span>new</span> <span>TenantDataSource</span><span>();</span>
       <span>}</span>
   <span>}</span>
   @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: 

   <span>@Bean</span><span>(</span><span>name</span> <span>=</span> <span>"tenantA-dataSource"</span><span>)</span>
   <span>public</span> <span>TenantDataSource</span> <span>tenantADataSource</span><span>()</span> <span>{</span>
       <span>return</span> <span>new</span> <span>TenantDataSource</span><span>();</span>
   <span>}</span>
   <span>@Bean</span><span>(</span><span>name</span> <span>=</span> <span>"tenantB-dataSource"</span><span>)</span>
   <span>public</span> <span>TenantDataSource</span> <span>tenantBDataSource</span><span>()</span> <span>{</span>
       <span>return</span> <span>new</span> <span>TenantDataSource</span><span>();</span>
   <span>}</span>
   <span>@Bean</span><span>(</span><span>name</span> <span>=</span> <span>"tenantA-dataSource"</span><span>)</span>
   <span>public</span> <span>TenantDataSource</span> <span>tenantADataSource</span><span>()</span> <span>{</span>
       <span>return</span> <span>new</span> <span>TenantDataSource</span><span>();</span>
   <span>}</span>

   <span>@Bean</span><span>(</span><span>name</span> <span>=</span> <span>"tenantB-dataSource"</span><span>)</span>
   <span>public</span> <span>TenantDataSource</span> <span>tenantBDataSource</span><span>()</span> <span>{</span>
       <span>return</span> <span>new</span> <span>TenantDataSource</span><span>();</span>
   <span>}</span>
   @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: 

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

       <span>private</span> <span>String</span> <span>tenantName</span><span>;</span>
       <span>private</span> <span>String</span> <span>databaseUrl</span><span>;</span>

       <span>@Override</span>
       <span>public</span> <span>void</span> <span>setBeanName</span><span>(</span><span>String</span> <span>beanName</span><span>)</span> <span>{</span>
           <span>// Extract tenant name from the bean name</span>
           <span>if</span> <span>(</span><span>beanName</span><span>.</span><span>contains</span><span>(</span><span>"-"</span><span>))</span> <span>{</span>
               <span>this</span><span>.</span><span>tenantName</span> <span>=</span> <span>beanName</span><span>.</span><span>split</span><span>(</span><span>"-"</span><span>)[</span><span>0</span><span>];</span>
           <span>}</span> <span>else</span> <span>{</span>
               <span>throw</span> <span>new</span> <span>IllegalArgumentException</span><span>(</span><span>"Invalid bean naming convention. Expected format: <tenantName>-dataSource"</span><span>);</span>
           <span>}</span>

           <span>// Assign a database URL dynamically based on the tenant name</span>
           <span>this</span><span>.</span><span>databaseUrl</span> <span>=</span> <span>"jdbc:mysql://localhost:3306/"</span> <span>+</span> <span>tenantName</span> <span>+</span> <span>"_db"</span><span>;</span>
       <span>}</span>

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

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

       <span>private</span> <span>final</span> <span>TenantDataSource</span> <span>tenantADataSource</span><span>;</span>
       <span>private</span> <span>final</span> <span>TenantDataSource</span> <span>tenantBDataSource</span><span>;</span>

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

       <span>public</span> <span>void</span> <span>processTenantData</span><span>()</span> <span>{</span>
           <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>"Processing data for all tenants..."</span><span>);</span>
           <span>tenantADataSource</span><span>.</span><span>connect</span><span>();</span>
           <span>tenantBDataSource</span><span>.</span><span>connect</span><span>();</span>
       <span>}</span>
   <span>}</span>
   @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: 

     <span>TenantService</span> <span>tenantService</span> <span>=</span> <span>context</span><span>.</span><span>getBean</span><span>(</span><span>TenantService</span><span>.</span><span>class</span><span>);</span>
     <span>TenantService</span> <span>tenantService</span> <span>=</span> <span>context</span><span>.</span><span>getBean</span><span>(</span><span>TenantService</span><span>.</span><span>class</span><span>);</span>
     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(): 

   <span>tenantService</span><span>.</span><span>processTenantData</span><span>();</span>
   <span>tenantService</span><span>.</span><span>processTenantData</span><span>();</span>
   tenantService.processTenantData();

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Code in TenantService: 

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

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

原文链接：spring-002: setBeanName()-of-BeanNameAware-BeanFactory

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