Spring Boot基础教程10-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

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", newCustomServlet()).addMapping("/roncoo");

servletContext.addFilter("customFilter", new CustomFilter())

.addMappingForServletNames(EnumSet.of(DispatcherType.REQUEST), 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