Spring Boot - Web 应用开发 - Servlet, Filter, Listener

1. 在 Spring Boot 中的三种实现方式

(1) 方法一：通过注册

ServletRegistrationBean

、

FilterRegistrationBean

和

ServletListenerRegistrationBean

获得控制

public class CustomerServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("Servlet get method");
doPost(req, resp);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("Servlet post method");
resp.getWriter().write("hello world");
}
}

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");
}

}

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");
}

}

@Bean
public ServletRegistrationBean servletRegistrationBean() {
return new ServletRegistrationBean(new CustomerServlet(), "/oktfolio");
}

@Bean
public FilterRegistrationBean filterRegistrationBean() {
return new FilterRegistrationBean(new CustomFilter()/*, servletRegistrationBean()*/);
}

@Bean
public ServletListenerRegistrationBean<CustomListener> servletListenerRegistrationBean() {
return new ServletListenerRegistrationBean<CustomListener>(new CustomListener());
}

(2) 方法二：通过实现

ServletContextInitializer

接口直接注册

@Override
public void onStartup(ServletContext servletContext) throws ServletException {
servletContext.addServlet("customServlet", new CustomerServlet()).addMapping("/oktfolio");
servletContext.addFilter("customFilter", new CustomFilter()).addMappingForServletNames(EnumSet.of
(DispatcherType.REQUEST), true, "customServlet");
servletContext.addListener(new CustomListener());
}

(3) 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