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"); } }