Servlet3.0

1：ServletContainerInitializer

ServletContainerInitializer是Servlet3.0提供的用于注册Servlet、Filter、Listener三大组件的控件。在初始化是可以操作感兴趣的类，功能强大。
具体示例如下：

//ServletContainerInitializer注册Servlet、Filter、Listener
@HandlesTypes(value = {HelloService.class})
public class MyServletContainerInitalizer implements ServletContainerInitializer {
    @Override
    public void onStartup(Set<Class<?>> set, ServletContext servletContext) throws ServletException {
        System.out.println("感兴趣的类型。。。");
        for(Class<?> cls : set) {
            System.out.println(cls);
        }

        ServletRegistration.Dynamic servlet = servletContext.addServlet("helloServlet", HelloServlet.class);
        servlet.addMapping("/user");

        servletContext.addListener(HelloListener.class);

        FilterRegistration.Dynamic dFilter = servletContext.addFilter("userFilter", EncodingFilter.class);
        dFilter.addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST),true,"/*");
    }
}

HelloServlet.class、HelloListener.class、EncodingFilter.class分别为简单的示例，就不一一列出。
新建ServletContainerInitializer需要编写META-INF\services\javax.servlet.ServletContainerInitializer文件。

 具体项目目录如下：

├─.idea
│ ├─artifacts
│ └─libraries
├─src
│ └─main
│ ├─java
│ │ └─com
│ │ └─itranswarp
│ │ └─learnjava
│ │ ├─filter
│ │ ├─listener
│ │ ├─service
│ │ └─servlet
│ ├─resources
│ │ └─META-INF
│ │ └─services
│ └─webapp
│ └─WEB-INF

2：ServletContainerInitializer和Spring MVC

通过ServletContainerInitializer可以整合注释的MVC。

主要代码如下：

MyWebAppInitializer 类：

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

//Web容器启动的时候创建对象；调用容器来初始化配置和前端控制器
public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    //获取根容器的配置文件（Spring配置文件） 父容器
    protected Class<?>[] getRootConfigClasses() {
        return new Class[] {RootConfig.class};
    }

    //获取web容器配置信息，子容器
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{AppConfig.class};
    }

    //获取DispatchServlet的映射信息
    // /:拦截所有静态请求，但不包括*.jsp
    protected String[] getServletMappings() {
        return new String[] {"/"};
    }
}

AppConfig类：

//只扫描Controller，子容器
//useDefaultFilters = false
@ComponentScan(value = "com.itranswarp.learnjava.mvc",includeFilters = {
        @ComponentScan.Filter(type= FilterType.ANNOTATION,classes={Controller.class})},useDefaultFilters = false)
@EnableWebMvc
public class AppConfig extends WebMvcConfigurerAdapter {
    //资源配置器
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        registry.jsp("/WEB-INF/views/",".jsp");
    }

    //静态资源访问
    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }

//    //拦截器
//    @Override
//    public void addInterceptors(InterceptorRegistry registry) {
//        //super.addInterceptors(registry);
//        registry.addInterceptor(new MyFristInterceptor()).addPathPatterns("/**");
//    }
}

RootConfig 类：

//根容器，扫描出Controller外的其他注解，父容器
@ComponentScan(value = "com.itranswarp.learnjava.mvc",excludeFilters = {
        @ComponentScan.Filter(type= FilterType.ANNOTATION,classes={Controller.class})
})
public class RootConfig {

}

3：异步操作
Servlet通过asyncSupported = true开始异步操作。
具体测试代码

@WebServlet(value = "/asyc",asyncSupported = true)
public class HelloAsycServlet extends HttpServlet {
    protected void doGet(final HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        final AsyncContext asyncContext = request.startAsync();
        System.out.println("主线程开始：" + Thread.currentThread());
        asyncContext.start(new Runnable() {
            public void run() {
                System.out.println("副线程开始：" + Thread.currentThread());
                try {
                   sayHello();
                   asyncContext.complete();
                   AsyncContext asyncContext1 = request.getAsyncContext();
                    ServletResponse servletResponse = asyncContext1.getResponse();
                    PrintWriter pw = servletResponse.getWriter();
                    pw.write("hello asyc...");
                    System.out.println("副线程结束：" + Thread.currentThread());
                    pw.flush();
                } catch (Exception e) {

                }
            }
        });

        System.out.println("主线程结束：" + Thread.currentThread());
    }

    private void sayHello() throws InterruptedException {
        System.out.println("proceeding...");
        Thread.sleep(3000);
    }

}

Spring MVC也基于Servlet3.0提供了相关异步操作。

Callable比较简单，具体如下：

@ResponseBody
@RequestMapping("/asyc01")
public Callable<String> asyc01() {
    System.out.println("主线程开始：" + Thread.currentThread());
    Callable<String> callable = new Callable<String>() {
        public String call() throws Exception {
            System.out.println("副线程开始：" + Thread.currentThread());
            Thread.sleep(2000);
            System.out.println("副线程结束：" + Thread.currentThread());
            return "allable<String> asyc01()";
        }
    };

    System.out.println("主线程结束：" + Thread.currentThread());
    return callable;
}

DeferredResult为另一种方式：

@ResponseBody
@RequestMapping("/createOrder")
public DeferredResult<Object> createOrder() {

    DeferredResult<Object> deferredResult = new DeferredResult<Object>((long)3000,"create fail...");
    DeferedResultQueue.save(deferredResult);
    return deferredResult;
}

@ResponseBody
@RequestMapping("/create")
public String create() {
    String order = UUID.randomUUID().toString();
    DeferredResult<Object> deferredResult = DeferedResultQueue.get();
    deferredResult.setResult(order);
    return "success===>" + order;
}

public class DeferedResultQueue {
    private static Queue<DeferredResult<Object>> queue = new ConcurrentLinkedDeque<DeferredResult<Object>>();

    public static void save(DeferredResult<Object> deferredResult) {
        queue.add(deferredResult);
    }

    public static DeferredResult<Object> get() {
       return queue.poll();
    }
}




以上内容来自网上视频教程，再次表示感谢。