spring boot-Servlets, Filters, l

一.Web开发使用 Controller 基本上可以完成大部分需求,但是我们还可能会用到 Servlet、 Filter、 Listener 等等
二.在 spring boot 中的三种实现方式
方法一:通过注册 ServletRegistrationBean、 FilterRegistrationBean 和 ServletListenerRegistrationBean 获得控制

/**
* 自定义 servlet *
* @author wujing */
public class CustomServlet extends HttpServlet {
/** *
  */
 private static final long serialVersionUID = 1L;
 @Override
 protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    System.out.println("servlet get method");
    doPost(request, response);
}
 @Override
 protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    System.out.println("servlet post method");
    response.getWriter().write("hello world");
} }
/**
* 自定义 filter *
* @author wujing */
public class CustomFilter implements Filter {
 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
    System.out.println("init filter");
 }
 @Override
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
        throws IOException, ServletException {
    System.out.println("do filter");
    chain.doFilter(request, response);
}
 @Override
 public void destroy() {
    System.out.println("destroy filter");
 }
}
/**
* 自定义 listener *
* @author wujing */
public class CustomListener implements ServletContextListener {
 @Override
 public void contextInitialized(ServletContextEvent sce) {
    System.out.println("contextInitialized");
 }
 @Override
 public void contextDestroyed(ServletContextEvent sce) {
    System.out.println("contextDestroyed");
 }
}

注册 bean

  @Bean
  public ServletRegistrationBean servletRegistrationBean() {
      return new ServletRegistrationBean(new CustomServlet(), "/roncoo");
  }
  @Bean
  public FilterRegistrationBean filterRegistrationBean() {
     return new FilterRegistrationBean(new CustomFilter(), servletRegistrationBean());
  }
  @Bean
  public ServletListenerRegistrationBean<CustomListener> servletListenerRegistrationBean() {
    return new ServletListenerRegistrationBean<CustomListener>(new CustomListener()); 
  }

方法二:通过实现 ServletContextInitializer 接口直接注册

implements ServletContextInitializer {
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
  servletContext.addServlet("customServlet", new CustomServlet()).addMapping("/roncoo");
  servletContext.addFilter("customFilter", new CustomFilter())
.addMappingForServletNames(EnumSet.of(DispatcherType.REQUES T), true, "customServlet");
servletContext.addListener(new CustomListener()); 
}

方法三:在SpringBootApplication 上使用@ServletComponentScan 注解后,直接通过@WebServlet、 @WebFilter、@WebListener 注解自动注册