spring boot中@WebListener、@WebFilter（也就是自定义servlet）不起作用的解决方案

在Spring Boot中，当需要以注解的方式添加session监听器或其他servlet(包括监听器、过滤器、以及自定义的servlet)时，为了让其生效，还需要在配置类上添加@ServletComponentScan注解，该注解的作用是告诉spring boot,让其自动管理servlet，否则注解方式注册的servlet不起作用

1. 定义过滤器

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

/**
 * 使用注解标注过滤器@WebFilter将一个实现了javax.servlet.Filter接口的类定义为过滤器
 * filterName声明过滤器的名称（可选）
 * urlPatterns指定要过滤的URL模式,也可使用属性value来声明.(指定要过滤的URL模式是必选属性)
 * 

 * Created by [email protected] on 2017/2/24.
 */
@WebFilter(filterName = "myFilter", urlPatterns = "/*")
public class MyFilter implements Filter {
    private Logger logger = LoggerFactory.getLogger(MyFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        logger.info("过滤器：myFilter >>>> 初始化");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        logger.info("过滤器：myFilter >>>> 执行过滤操作");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {
        logger.info("过滤器：myFilter >>>> 销毁");
    }
}

2. 定义监听器

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

/**
 * HttpSession监听器
 * 

 * Created by [email protected] on 2017/2/24.
 */
@WebListener
public class MyHttpSessionListener implements HttpSessionListener {
    private Logger logger = LoggerFactory.getLogger(MyHttpSessionListener.class);

    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        logger.info("监听器：Session >>>> 创建");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        logger.info("监听器：Session >>>> 销毁");
    }
}

3. 自定义servlet

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

/**
 * 自定义Servlet
 * 

 * Created by [email protected] on 2017/2/24.
 */
public class MyServlet1 extends HttpServlet {
    private Logger logger = LoggerFactory.getLogger(MyServlet1.class);

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        logger.info("已执行：MyServlet1.doGet()");
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        logger.info("已执行：MyServlet1.doPost()");
        resp.setContentType("text/html");
        resp.setCharacterEncoding("UTF-8"); //  设置编码，解决中文乱码问题

        PrintWriter out = resp.getWriter();
        out.println("");
        out.println("");
        out.println("");
        out.println("");
        out.println("");
        out.println("
这是：MyServlet1
");
        out.println("");
        out.println("");
    }
}

配置@ServletComponentScan以使以上servlet生效

@SpringBootApplication
@ServletComponentScan
public class BasicApp extends WebMvcConfigurerAdapter{

    @Bean
    public ServletRegistrationBean myServlet1() {
        return new ServletRegistrationBean(new MyServlet1(),"/myServlet1/*");
    }

    public static void main(String[] args) {
        SpringApplication.run(BasicApp.class, args);
    }
}