[Spring Boot] Complex Scope Scenarios of a Spring Bean - Mix Prototype and Singleton, ScopeProxy

We have the following example:

@SpringBootApplication
public class In28minutesScopeApplication {

    private static Logger LOGGER = LoggerFactory.getLogger(In28minutesScopeApplication.class);

    public static void main(String[] args) {
        // Application Context
        ApplicationContext applicationContext =
                SpringApplication.run(In28minutesScopeApplication.class, args);
        PersonDAO personDAO = applicationContext.getBean(PersonDAO.class);
        PersonDAO personDAO1 = applicationContext.getBean(PersonDAO.class);

        LOGGER.info("{}", personDAO);
        LOGGER.info("{}", personDAO.getJdbcConnection());

        LOGGER.info("{}", personDAO1);
        LOGGER.info("{}", personDAO1.getJdbcConnection());

    }
}

@Component
public class PersonDAO {

    @Autowired
    JDBCConnection jdbcConnection;

    public JDBCConnection getJdbcConnection() {
        return jdbcConnection;
    }

    public void setJdbcConnection(JDBCConnection jdbcConnection) {
        this.jdbcConnection = jdbcConnection;
    }
}


@Component
public class JDBCConnection {
    public JDBCConnection () {
        System.out.println("JDBC Connection");
    }
}

 

The idea is to understand in different cases, how those instanse are created.

Currently when running the application, we got:

com.example.in28minutes.scope.PersonDAO@6c61a903
com.example.in28minutes.scope.JDBCConnection@59d4cd39

com.example.in28minutes.scope.PersonDAO@6c61a903
com.example.in28minutes.scope.JDBCConnection@59d4cd39

Each class share the same instanse.

 

What if we want that 'PersonDAO' using Singleton but JDBCConnection use 'Prototype'?

@Component
@Scope(ConfigurableBeanFactory.SCOPE_SINGLETON)
public class PersonDAO {

    @Autowired
    JDBCConnection jdbcConnection;

    public JDBCConnection getJdbcConnection() {
        return jdbcConnection;
    }

    public void setJdbcConnection(JDBCConnection jdbcConnection) {
        this.jdbcConnection = jdbcConnection;
    }
}

@Component
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class JDBCConnection {
    public JDBCConnection () {
        System.out.println("JDBC Connection");
    }
}

 

In the end, we got the same result:

com.example.in28minutes.scope.PersonDAO@14008db3
com.example.in28minutes.scope.JDBCConnection@16aa8654
com.example.in28minutes.scope.PersonDAO@14008db3
com.example.in28minutes.scope.JDBCConnection@16aa8654

 

If we really want JDBCConnection use a different instance, we can add Proxy to it:

@Component
@Scope(value = ConfigurableBeanFactory.SCOPE_PROTOTYPE, proxyMode = ScopedProxyMode.TARGET_CLASS)
public class JDBCConnection {
    public JDBCConnection () {
        System.out.println("JDBC Connection");
    }
}