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。1、自定义servlet
/*** 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"); }} 2、自定义filter
/** * 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"); }} 3、自定义listener
/** * 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"); }} 4、在启动类里面注册bean
@Beanpublic ServletRegistrationBean servletRegistrationBean() { return new ServletRegistrationBean(new CustomServlet(), "/roncoo");}@Beanpublic FilterRegistrationBean filterRegistrationBean() { //return new FilterRegistrationBean(new CustomFilter(), servletRegistrationBean());表示仅对/roncoo进行拦截；return new FilterRegistrationBean(new CustomFilter());表示对所有请求进行拦截 return new FilterRegistrationBean(new CustomFilter(), servletRegistrationBean());}@Beanpublic ServletListenerRegistrationBean servletListenerRegistrationBean() { return new ServletListenerRegistrationBean (new CustomListener());} 方法二：启动类通过实现 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.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 1、自定义servlet
import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 自定义servlet * * @author wujing */@WebServlet(name = "customServlet", urlPatterns = "/roncoo")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"); response.flushBuffer(); }} 2、自定义filter
import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.annotation.WebFilter;/** * @author wujing */// /*表示对所有请求进行拦截 /roncoo 表示仅对该请求拦截@WebFilter(filterName = "customFilter", urlPatterns = "/*")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"); }} 3、自定义listener
import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener;/** * @author wujing */@WebListenerpublic class CustomListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent sce) { System.out.println("contextInitialized"); } @Override public void contextDestroyed(ServletContextEvent sce) { System.out.println("contextDestroyed"); }} 4、启动类
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.boot.web.servlet.ServletComponentScan;@ServletComponentScan@SpringBootApplicationpublic class SpringBootDemo103Application { public static void main(String[] args) { SpringApplication.run(SpringBootDemo103Application.class, args); }}