Implementations of this SPI will be detected automatically by {@link * SpringServletContainerInitializer}, which itself is bootstrapped automatically * by any Servlet 3.0 container. See {@linkplain SpringServletContainerInitializer its * Javadoc} for details on this bootstrapping mechanism. * *
* {@code
*
* dispatcher
*
* org.springframework.web.servlet.DispatcherServlet
*
*
* contextConfigLocation
* /WEB-INF/spring/dispatcher-config.xml
*
* 1
*
*
*
* dispatcher
* /
* }
*
*
* public class MyWebAppInitializer implements WebApplicationInitializer {
*
* @Override
* public void onStartup(ServletContext container) {
* XmlWebApplicationContext appContext = new XmlWebApplicationContext();
* appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
*
* ServletRegistration.Dynamic dispatcher =
* container.addServlet("dispatcher", new DispatcherServlet(appContext));
* dispatcher.setLoadOnStartup(1);
* dispatcher.addMapping("/");
* }
*
* }
*
* As an alternative to the above, you can also extend from {@link
* org.springframework.web.servlet.support.AbstractDispatcherServletInitializer}.
*
* As you can see, thanks to Servlet 3.0's new {@link ServletContext#addServlet} method
* we're actually registering an instance of the {@code DispatcherServlet}, and
* this means that the {@code DispatcherServlet} can now be treated like any other object
* -- receiving constructor injection of its application context in this case.
*
* This style is both simpler and more concise. There is no concern for dealing with * init-params, etc, just normal JavaBean-style properties and constructor arguments. You * are free to create and work with your Spring application contexts as necessary before * injecting them into the {@code DispatcherServlet}. * *
Most major Spring Web components have been updated to support this style of * registration. You'll find that {@code DispatcherServlet}, {@code FrameworkServlet}, * {@code ContextLoaderListener} and {@code DelegatingFilterProxy} all now support * constructor arguments. Even if a component (e.g. non-Spring, other third party) has not * been specifically updated for use within {@code WebApplicationInitializers}, they still * may be used in any case. The Servlet 3.0 {@code ServletContext} API allows for setting * init-params, context-params, etc programmatically. * *
* public class MyWebAppInitializer implements WebApplicationInitializer {
*
* @Override
* public void onStartup(ServletContext container) {
* // Create the 'root' Spring application context
* AnnotationConfigWebApplicationContext rootContext =
* new AnnotationConfigWebApplicationContext();
* rootContext.register(AppConfig.class);
*
* // Manage the lifecycle of the root application context
* container.addListener(new ContextLoaderListener(rootContext));
*
* // Create the dispatcher servlet's Spring application context
* AnnotationConfigWebApplicationContext dispatcherContext =
* new AnnotationConfigWebApplicationContext();
* dispatcherContext.register(DispatcherConfig.class);
*
* // Register and map the dispatcher servlet
* ServletRegistration.Dynamic dispatcher =
* container.addServlet("dispatcher", new DispatcherServlet(dispatcherContext));
* dispatcher.setLoadOnStartup(1);
* dispatcher.addMapping("/");
* }
*
* }
*
* As an alternative to the above, you can also extend from {@link
* org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer}.
*
* Remember that {@code WebApplicationInitializer} implementations are detected
* automatically -- so you are free to package them within your application as you
* see fit.
*
* {@code WEB-INF/web.xml} and {@code WebApplicationInitializer} use are not mutually * exclusive; for example, web.xml can register one servlet, and a {@code * WebApplicationInitializer} can register another. An initializer can even * modify registrations performed in {@code web.xml} through methods such as * {@link ServletContext#getServletRegistration(String)}. However, if * {@code WEB-INF/web.xml} is present in the application, its {@code version} attribute * must be set to "3.0" or greater, otherwise {@code ServletContainerInitializer} * bootstrapping will be ignored by the servlet container. * *
Apache Tomcat maps its internal {@code DefaultServlet} to "/", and on Tomcat versions * <= 7.0.14, this servlet mapping cannot be overridden programmatically. * 7.0.15 fixes this issue. Overriding the "/" servlet mapping has also been tested * successfully under GlassFish 3.1.
* * @author Chris Beams * @since 3.1 * @see SpringServletContainerInitializer * @see org.springframework.web.context.AbstractContextLoaderInitializer * @see org.springframework.web.servlet.support.AbstractDispatcherServletInitializer * @see org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer */ public interface WebApplicationInitializer { /** * Configure the given {@link ServletContext} with any servlets, filters, listeners * context-params and attributes necessary for initializing this web application. See * examples {@linkplain WebApplicationInitializer above}. * @param servletContext the {@code ServletContext} to initialize * @throws ServletException if any call against the given {@code ServletContext} * throws a {@code ServletException} */ void onStartup(ServletContext servletContext) throws ServletException; }