1. Filter

import javax.servlet.*;
import java.io.IOException;

public class MyFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("MyFilter process...");
        chain.doFilter(request,response);

    }

    @Override
    public void destroy() {

    }
}

2. listener

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce) {
        System.out.println("contextInitialized...web应用启动");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        System.out.println("contextDestroyed...当前web项目销毁");
    }
}

3. servlet

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class MyServlet extends HttpServlet {

    //处理get请求
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.getWriter().write("Hello MyServlet");
    }
}

4. 配置三大组件

@Configuration
public class MyServerConfig {

    //注册三大组件
    @Bean
    public ServletRegistrationBean myServlet(){
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(),"/myServlet");
        registrationBean.setLoadOnStartup(1);
        return registrationBean;
    }

    @Bean
    public FilterRegistrationBean myFilter(){
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new MyFilter());
        registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
        return registrationBean;
    }

    @Bean
    public ServletListenerRegistrationBean myListener(){
        ServletListenerRegistrationBean<MyListener> registrationBean = new ServletListenerRegistrationBean<>(new MyListener());
        return registrationBean;
    }


    //配置嵌入式的Servlet容器
    @Bean
    public EmbeddedServletContainerCustomizer embeddedServletContainerCustomizer(){
        return new EmbeddedServletContainerCustomizer() {

            //定制嵌入式的Servlet容器相关的规则
            @Override
            public void customize(ConfigurableEmbeddedServletContainer container) {
                container.setPort(8083);
            }
        };
    }

}

5. WebMvcConfigurer

初学者会把webmvcconfigurer里面的某些配置跟Javaweb三大组件搞混。

***（Interceptor）和过滤器（Filter）的区别

Spring的Interceptor(***)与Servlet的Filter有相似之处，比如二者都是AOP编程思想的体现，都能实现权限检查、日志记录等。不同的是：