感觉ServletRegistrationBean在Springboot中是一个可以看懂的类，好像作用就相当于@Controoller注解，
package org.springframework.boot.web.servlet; /**
* A {@link ServletContextInitializer} to register {@link Servlet}s in a Servlet 3.0+
* container. Similar to the {@link ServletContext#addServlet(String, Servlet)
* registration} features provided by {@link ServletContext} but with a Spring Bean
* friendly design.
* <p>
* The {@link #setServlet(Servlet) servlet} must be specified before calling
* {@link #onStartup}. URL mapping can be configured used {@link #setUrlMappings} or
* omitted when mapping to '/*' (unless
* {@link #ServletRegistrationBean(Servlet, boolean, String...) alwaysMapUrl} is set to
* {@code false}). The servlet name will be deduced if not specified.
*
* @param <T> the type of the {@link Servlet} to register
* @author Phillip Webb
* @since 1.4.0
* @see ServletContextInitializer
* @see ServletContext#addServlet(String, Servlet)
*/
public class ServletRegistrationBean<T extends Servlet>
extends DynamicRegistrationBean<ServletRegistration.Dynamic> { private static final String[] DEFAULT_MAPPINGS = { "/*" }; private T servlet; private Set<String> urlMappings = new LinkedHashSet<>(); private boolean alwaysMapUrl = true; private int loadOnStartup = -1; private MultipartConfigElement multipartConfig; /**
* Create a new {@link ServletRegistrationBean} instance.
*/
public ServletRegistrationBean() {
} /**
* Create a new {@link ServletRegistrationBean} instance with the specified
* {@link Servlet} and URL mappings.
* @param servlet the servlet being mapped
* @param urlMappings the URLs being mapped
*/
public ServletRegistrationBean(T servlet, String... urlMappings) {
this(servlet, true, urlMappings);
} /**
* Create a new {@link ServletRegistrationBean} instance with the specified
* {@link Servlet} and URL mappings.
* @param servlet the servlet being mapped
* @param alwaysMapUrl if omitted URL mappings should be replaced with '/*'
* @param urlMappings the URLs being mapped
*/
public ServletRegistrationBean(T servlet, boolean alwaysMapUrl,
String... urlMappings) {
Assert.notNull(servlet, "Servlet must not be null");
Assert.notNull(urlMappings, "UrlMappings must not be null");
this.servlet = servlet;
this.alwaysMapUrl = alwaysMapUrl;
this.urlMappings.addAll(Arrays.asList(urlMappings));
}
很多这样的bean最后交给了Spring管理。