I have some questions about spring’s initialization in different environment.
1. In web container context, such as tomcat.
I knew that spring can be initialized by declaring
org.springframework.web.context.ContextLoaderListener in <listener-class> field.
It will be initialized automatically when tomcat is started. (I think this is right :-） )
2. In JUnit context
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:appContext.xml")
annotations can be used to initialize the Spring context.
Under these two cases, we can use such as
@Autowired
private ServiceDao serviceDao;
to use the serviceDao, and we almost never used the ApplicationContext.getBean() method.
3. In a common J2SE environment
Should I must initialize the spring context manually,
ApplicationContext appContext = new FileSystemXmlApplicationContext(xx.xml)
and then use appContext.getBean(XX) to get the bean?
in this case, can @Autowired be used?
How to do this?
Updated:
I try the spring-boot, I think the variable can be autowired, because the class is annotated with @Component， and with the @ComponentScan in main class, the variable can be autowired.
But I used spring xml before, and I have some injection like this, I don’t know how to autowire the variable.
<bean id="XXXMap" class="com.xx">
<property name="handlerMap">
<map>
<entry key="XXX" value="YYY"/>
</map>
</property>
</bean>
use the @component, I believe XXXMap can be autowired, but how the map is initialized?
Yes, you can use @Autowired no matter how you create the application context.
There are several ways to create an application context in a standalone application. You can of course still use the traditional XML configuration files but an alternative option worth considering is spring-boot. It allows you to create completely annotation driven applications that mostly rely on conventions over configuration. Bootstrapping a simple standalone application reduces to:
@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Main implements CommandLineRunner {
@Autowired
private UserService userService;
public void run(String... args) throws Exception {
System.out.println(userService.findUser(42L));
}
public static void main(String[] args) {
SpringApplication.run(Main.class, args);
}
}
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