springboot系列教程（九）——Servlet、Filter、Listener

小咪咪 2022-06-01 23:17 194阅读 0赞

## 方式一 ##

**新建servlet**

/** * @author :小虎 * @date :2017/12/27 */
    
    @WebServlet(name = "IndexServlet",urlPatterns = "/hello")
    public class IndexServlet extends HttpServlet{ 
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            resp.getWriter().print("hello word");
            resp.getWriter().flush();
            resp.getWriter().close();
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            super.doPost(req, resp);
        }
    }

**新建IndexFilter**

package com.example.demo.filter;
    
    import javax.servlet.*;
    import javax.servlet.annotation.WebFilter;
    import java.io.IOException;
    
    /** * @author :小虎 * @date :2017/12/27 */
    
    
    @WebFilter(urlPatterns = "/*", filterName = "indexFilter")
    public class IndexFilter implements Filter { 
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            System.out.println("init IndexFilter");
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            System.out.println("doFilter IndexFilter");
            filterChain.doFilter(servletRequest,servletResponse);
    
        }
    
        @Override
        public void destroy() {
    
        }
    }

**新建IndexListener**

package com.example.demo.filter;
    
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    import javax.servlet.annotation.WebListener;
    
    /** * @author :小虎 * @date :2017/12/27 */
    
    
    @WebListener
    public class IndexListener implements ServletContextListener { 
    
        @Override
        public void contextInitialized(ServletContextEvent servletContextEvent) {
            System.out.println("IndexListener contextInitialized");
        }
    
        @Override
        public void contextDestroyed(ServletContextEvent servletContextEvent) {
    
        }
    }

**上面配置完了，需要配置一个核心的注解@ServletComponentScan,具体配置项如下，可以配置扫描的路径**

## 方式二 ##

**新建IndexFilter1**

package com.example.demo.config;
    
    import javax.servlet.*;
    import java.io.IOException;
    
    /** * @author :小虎 * @date :2017/12/27 */
    
    
    public class IndexFilter1 implements Filter { 
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            System.out.println("init IndexFilter111");
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            System.out.println("doFilter IndexFilter111");
            filterChain.doFilter(servletRequest,servletResponse);
    
        }
    
        @Override
        public void destroy() {
    
        }
    }

**新建IndexListener1**

package com.example.demo.config;
    
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    
    /** * @author :小虎 * @date :2017/12/27 */
    
    
    public class IndexListener1 implements ServletContextListener { 
    
        @Override
        public void contextInitialized(ServletContextEvent servletContextEvent) {
            System.out.println("IndexListener1111 contextInitialized");
        }
    
        @Override
        public void contextDestroyed(ServletContextEvent servletContextEvent) {
    
        }
    }

**新建IndexServlet1**

package com.example.demo.config;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    /** * @author :小虎 * @date :2017/12/27 */
    
    public class IndexServlet1 extends HttpServlet{ 
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            resp.getWriter().print("hello word11111");
            resp.getWriter().flush();
            resp.getWriter().close();
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            super.doPost(req, resp);
        }
    }

**新建WebConfig**

package com.example.demo.config;
    
    import org.springframework.boot.web.servlet.FilterRegistrationBean;
    import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
    import org.springframework.boot.web.servlet.ServletRegistrationBean;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    /** * @author :小虎 * @date :2017/12/27 */
    
    @Configuration
    public class WebConfig { 
        @Bean
        public ServletRegistrationBean indexServletRegistration() {
            ServletRegistrationBean registration = new ServletRegistrationBean(new IndexServlet1());
            registration.addUrlMappings("/hello1");
            return registration;
        }
    
        @Bean
        public FilterRegistrationBean indexFilterRegistration() {
            FilterRegistrationBean registration = new FilterRegistrationBean(new IndexFilter1());
            registration.addUrlPatterns("/");
            return registration;
        }
        @Bean
        public ServletListenerRegistrationBean servletListenerRegistrationBean(){
            ServletListenerRegistrationBean servletListenerRegistrationBean = new ServletListenerRegistrationBean();
            servletListenerRegistrationBean.setListener(new IndexListener1());
            return servletListenerRegistrationBean;
        }
    }

### 总结 ###

> 两种方案在使用上有差别，但是在内部SpringBoot的实现上是无差别的，即使使用的是Servlet3.0注解，也是通过扫描注解  
> 转换成这三种bean的FilterRegistrationBean、ServletRegistrationBean、ServletListenerRegistrationBean

### 扩展 ###

> 大家在使用的时候有没有发觉，其实SpringBoot在使用SpringMvc的时候不需要配置DispatcherServlet的，因为已经自动配置了， 但是如果想要加一些初始配置参数如何解决，方案如下：

@Bean
        public ServletRegistrationBean dispatcherRegistration(DispatcherServlet dispatcherServlet) {
            ServletRegistrationBean registration = new ServletRegistrationBean(dispatcherServlet);
            registration.addUrlMappings("*.do");
            registration.addUrlMappings("*.json");
            return registration;
        }

**可以通过注入DispatcherServlet 然后用ServletRegistrationBean包裹一层 动态的加上一些初始参数**