Add a Servlet, Filter, or Listener to an Application
In a servlet stack application, that is with the spring-boot-starter-web, there are two ways to add Servlet, Filter, ServletContextListener, and the other listeners supported by the Servlet API to your application:
Add a Servlet, Filter, or Listener by Using a Spring Bean
To add a Servlet, Filter, or servlet *Listener by using a Spring bean, you must provide a @Bean definition for it.
Doing so can be very useful when you want to inject configuration or dependencies.
However, you must be very careful that they do not cause eager initialization of too many other beans, because they have to be installed in the container very early in the application lifecycle.
(For example, it is not a good idea to have them depend on your DataSource or JPA configuration.)
You can work around such restrictions by initializing the beans lazily when first used instead of on initialization.
In the case of filters and servlets, you can also add mappings and init parameters by adding a FilterRegistrationBean or a ServletRegistrationBean instead of or in addition to the underlying component.
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Like any other Spring bean, you can define the order of servlet filter beans; please make sure to check the “Registering Servlets, Filters, and Listeners as Spring Beans” section.
Disable Registration of a Servlet or Filter
As described earlier, any Servlet or Filter beans are registered with the servlet container automatically.
To disable registration of a particular Filter or Servlet bean, create a registration bean for it and mark it as disabled, as shown in the following example:
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Java
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Kotlin
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration(proxyBeanMethods = false)
public class MyFilterConfiguration {
@Bean
public FilterRegistrationBean<MyFilter> registration(MyFilter filter) {
FilterRegistrationBean<MyFilter> registration = new FilterRegistrationBean<>(filter);
registration.setEnabled(false);
return registration;
}
}import org.springframework.boot.web.servlet.FilterRegistrationBean
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
@Configuration(proxyBeanMethods = false)
class MyFilterConfiguration {
@Bean
fun registration(filter: MyFilter): FilterRegistrationBean<MyFilter> {
val registration = FilterRegistrationBean(filter)
registration.isEnabled = false
return registration
}
}Add Servlets, Filters, and Listeners by Using Classpath Scanning
@WebServlet, @WebFilter, and @WebListener annotated classes can be automatically registered with an embedded servlet container by annotating a @Configuration class with @ServletComponentScan and specifying the package(s) containing the components that you want to register.
By default, @ServletComponentScan scans from the package of the annotated class.