ServletRegistrationBean的源码摘要

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));
    }