【Spring Boot】web应用开发-Servlets, Filters, listeners

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。

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

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/**

 

*自定义servlet

 

*

 

* @author wujing

 

*/

 

publicclass CustomServlet extends HttpServlet {

 

 

 

/**

 

*

 

*/

 

privatestatic final long serialVersionUID = 1L;

 

 

 

@Override

 

protectedvoid doGet(HttpServletRequest request, HttpServletResponse response)

 

throwsServletException, IOException {

 

System.out.println("servlet get method");

 

doPost(request, response);

 

}

 

 

 

@Override

 

protectedvoid doPost(HttpServletRequest request, HttpServletResponse response)

 

throwsServletException, IOException {

 

System.out.println("servlet post method");

 

response.getWriter().write("hello world");

 

}

 

 

 

}

 

 

 

/**

 

*自定义filter

 

*

 

* @author wujing

 

*/

 

publicclass CustomFilter implements Filter {

 

 

 

@Override

 

publicvoid init(FilterConfig filterConfig) throws ServletException {

 

System.out.println("init filter");

 

}

 

 

 

@Override

 

publicvoid doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

 

throwsIOException, ServletException {

 

System.out.println("do filter");

 

chain.doFilter(request, response);

 

}

 

 

 

@Override

 

publicvoid destroy() {

 

System.out.println("destroy filter");

 

}

 

 

 

}

 

 

 

/**

 

*自定义listener

 

*

 

* @author wujing

 

*/

 

publicclass CustomListener implements ServletContextListener {

 

 

 

@Override

 

publicvoid contextInitialized(ServletContextEvent sce) {

 

System.out.println("contextInitialized");

 

}

 

 

 

@Override

 

publicvoid contextDestroyed(ServletContextEvent sce) {

 

System.out.println("contextDestroyed");

 

}

 

 

 

}

 

注册bean

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@Bean

 

publicServletRegistrationBean servletRegistrationBean() {

 

returnnew ServletRegistrationBean(newCustomServlet(), "/roncoo");

 

}

 

 

 

@Bean

 

publicFilterRegistrationBean filterRegistrationBean() {

 

returnnew FilterRegistrationBean(newCustomFilter(), servletRegistrationBean());

 

}

 

 

 

@Bean

 

publicServletListenerRegistrationBean servletListenerRegistrationBean() {

 

returnnew ServletListenerRegistrationBean(newCustomListener());

 

}

 

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

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implementsServletContextInitializer {

 

 

 

@Override

 

publicvoidonStartup(ServletContextservletContext)throwsServletException {

 

servletContext.addServlet("customServlet",newCustomServlet()).addMapping("/roncoo");

 

servletContext.addFilter("customFilter",newCustomFilter())

 

.addMappingForServletNames(EnumSet.of(DispatcherType.REQUEST),true,"customServlet");

 

servletContext.addListener(newCustomListener());

 

}

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