package javax.servlet;

import java.util.EventListener;

public interface ServletContextListener extends EventListener {

    public void contextInitialized(ServletContextEvent sce);

    public void contextDestroyed(ServletContextEvent sce);
}

package javax.servlet;

import java.io.IOException;

public interface Filter {

    public void init(FilterConfig filterConfig) throws ServletException;
    
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException;

    public void destroy();
}

package javax.servlet;

import java.io.IOException;

public interface Servlet {

    public void init(ServletConfig config) throws ServletException;

    public ServletConfig getServletConfig();
    
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException;

    public String getServletInfo();
   
    public void destroy();
}

@WebListener
public class MyListener implements ServletContextListener {

    private Logger logger = LoggerFactory.getLogger(this.getClass());

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        logger.info("<<<<<<<<<<<<<< My listener start <<<<<<<<<<<<<<<<<<<<<<<");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        logger.info(">>>>>>>>>>>>>>> My lister end  >>>>>>>>>>>>>>>>>>>>>>>");
    }
}

@WebFilter(filterName = "myFilter", urlPatterns = "/*")
public class MyFilter implements Filter {

    private Logger logger = LoggerFactory.getLogger(this.getClass());

    @Override
    public void init(FilterConfig filterConfig) {
        logger.info("<<<<<<<<<<<<< MyFilter 初始化, config={}", filterConfig);
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        logger.info("=================== do filter ===============");
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() {
        logger.info(">>>>>>>>>>>>>>> destroy my filter >>>>>>>>>>>>>>>>>>>>>>>");
    }
}

@WebServlet(name = "showTime", urlPatterns = "/time")
public class ShowTimeServlet extends HttpServlet {

	private final Logger logger = LoggerFactory.getLogger(ShowTimeServlet.class);

	public ShowTimeServlet() {
		logger.info("ShowTimeServlet constructed!");
	}

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
		logger.info("show time servlet receive request,uri:{}", req.getRequestURI());
		resp.getWriter().write("ShowTime,现在时刻： " + new Date());
	}

	@Override
	public void init(ServletConfig config) throws ServletException {
		logger.info("ShowTime servlet 开始 init...");
		super.init(config);
	}

	@Override
	public void destroy() {
		logger.info("ShowTime servlet 开始 destroy...");
		super.destroy();
	}
}

package com.gpengtao.java.spi;

public interface SayHelloable {
    void say();
}

package com.gpengtao.java.spi;

public class SayChineseHello implements SayHelloable {
    @Override
    public void say() {
        System.out.println("哈喽");
    }
}

package com.gpengtao.java.spi;

public class SayEnglishHello implements SayHelloable {
    @Override
    public void say() {
        System.out.println("hello");
    }
}

package com.gpengtao.java.spi;

import org.junit.Test;

import java.util.ServiceLoader;

public class SPITest {

    @Test
    public void test() {
        ServiceLoader<SayHelloable> loader = ServiceLoader.load(SayHelloable.class);

        for (SayHelloable hello : loader) {
            System.out.println(hello);
            hello.say();
        }
    }
}

package javax.servlet;

import java.util.Set;

/**
 * Interface which allows a library/runtime to be notified of a web
 * application's startup phase and perform any required programmatic
 * registration of servlets, filters, and listeners in response to it.
 * 
 * <p>Implementations of this interface may be annotated with
 * {@link javax.servlet.annotation.HandlesTypes HandlesTypes}, in order to
 * receive (at their {@link #onStartup} method) the Set of application
 * classes that implement, extend, or have been annotated with the class
 * types specified by the annotation.
 * 
 * ......
 * 
 * @since Servlet 3.0
 */
public interface ServletContainerInitializer {

    public void onStartup(Set<Class<?>> c, ServletContext ctx) throws ServletException; 
}

/**
 * Servlet 3.0 {@link ServletContainerInitializer} designed to support code-based
 * configuration of the servlet container using Spring's {@link WebApplicationInitializer}
 * SPI as opposed to (or possibly in combination with) the traditional
 * {@code web.xml}-based approach.
 *
 * ......
 * 
 * @since 3.1
 */
@HandlesTypes(WebApplicationInitializer.class)
public class SpringServletContainerInitializer implements ServletContainerInitializer {

	/**
	 * Delegate the {@code ServletContext} to any {@link WebApplicationInitializer}
	 * implementations present on the application classpath.
	 * <p>Because this class declares @{@code HandlesTypes(WebApplicationInitializer.class)},
	 * Servlet 3.0+ containers will automatically scan the classpath for implementations
	 * of Spring's {@code WebApplicationInitializer} interface and provide the set of all
	 * such types to the {@code webAppInitializerClasses} parameter of this method.
	 * <p>If no {@code WebApplicationInitializer} implementations are found on the classpath,
	 * this method is effectively a no-op. An INFO-level log message will be issued notifying
	 * the user that the {@code ServletContainerInitializer} has indeed been invoked but that
	 * no {@code WebApplicationInitializer} implementations were found.
	 * <p>Assuming that one or more {@code WebApplicationInitializer} types are detected,
	 * they will be instantiated (and <em>sorted</em> if the @{@link
	 * org.springframework.core.annotation.Order @Order} annotation is present or
	 * the {@link org.springframework.core.Ordered Ordered} interface has been
	 * implemented). Then the {@link WebApplicationInitializer#onStartup(ServletContext)}
	 * method will be invoked on each instance, delegating the {@code ServletContext} such
	 * that each instance may register and configure servlets such as Spring's
	 * {@code DispatcherServlet}, listeners such as Spring's {@code ContextLoaderListener},
	 * or any other Servlet API componentry such as filters.
	 * @param webAppInitializerClasses all implementations of
	 * {@link WebApplicationInitializer} found on the application classpath
	 * @param servletContext the servlet context to be initialized
	 * @see WebApplicationInitializer#onStartup(ServletContext)
	 * @see AnnotationAwareOrderComparator
	 */
	@Override
	public void onStartup(Set<Class<?>> webAppInitializerClasses, ServletContext servletContext)
			throws ServletException {

		List<WebApplicationInitializer> initializers = new LinkedList<WebApplicationInitializer>();

		if (webAppInitializerClasses != null) {
			for (Class<?> waiClass : webAppInitializerClasses) {
				// Be defensive: Some servlet containers provide us with invalid classes,
				// no matter what @HandlesTypes says...
				if (!waiClass.isInterface() && !Modifier.isAbstract(waiClass.getModifiers()) &&
						WebApplicationInitializer.class.isAssignableFrom(waiClass)) {
					try {
						initializers.add((WebApplicationInitializer) waiClass.newInstance());
					}
					catch (Throwable ex) {
						throw new ServletException("Failed to instantiate WebApplicationInitializer class", ex);
					}
				}
			}
		}

		if (initializers.isEmpty()) {
			servletContext.log("No Spring WebApplicationInitializer types detected on classpath");
			return;
		}

		servletContext.log(initializers.size() + " Spring WebApplicationInitializers detected on classpath");
		AnnotationAwareOrderComparator.sort(initializers);
		for (WebApplicationInitializer initializer : initializers) {
			initializer.onStartup(servletContext);
		}
	}

}

import org.springframework.web.WebApplicationInitializer;

public class MyWebApplicationInitializer implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext container) {
        XmlWebApplicationContext appContext = new XmlWebApplicationContext();
        appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");

        ServletRegistration.Dynamic registration = container.addServlet("dispatcher", new DispatcherServlet(appContext));
        registration.setLoadOnStartup(1);
        registration.addMapping("/");
    }
}

public class MyWebApplicationInitializer implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext servletCxt) {

        // Load Spring web application configuration
        AnnotationConfigWebApplicationContext ac = new AnnotationConfigWebApplicationContext();
        ac.register(AppConfig.class);
        ac.refresh();

        // Create and register the DispatcherServlet
        DispatcherServlet servlet = new DispatcherServlet(ac);
        ServletRegistration.Dynamic registration = servletCxt.addServlet("app", servlet);
        registration.setLoadOnStartup(1);
        registration.addMapping("/app/*");
    }
}

public class MyWebAppInitializer extends AbstractDispatcherServletInitializer {

    @Override
    protected WebApplicationContext createRootApplicationContext() {
        return null;
    }

    @Override
    protected WebApplicationContext createServletApplicationContext() {
        XmlWebApplicationContext cxt = new XmlWebApplicationContext();
        cxt.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
        return cxt;
    }

    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    }
}

public class MyWebAppInitializer extends AbstractDispatcherServletInitializer {

    // ...

    @Override
    protected Filter[] getServletFilters() {
        return new Filter[] {
            new HiddenHttpMethodFilter(), new CharacterEncodingFilter() };
    }
}

public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class<?>[] { MyWebConfig.class };
    }

    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    }
}