spring-boot中servlet，过滤器，定时器，监听器使用

逃离我推掉我的手 2022-05-30 11:41 174阅读 0赞

*  [springBoot目录][springBoot]

--------------------

这一节介绍一下在spring-boot中怎么使用servlet,过滤器，监听器，拦截器。使用的方法有很几种，这里仅介绍我学会的一两种方法。  
目录结构：  
![这里写图片描述][70]

一、servlet  
采用注解的方式配置servlet,首先在入口类ServletApplication中添加注解`@ServletComponentScan`这样才会去扫描servlet的注解。  
其次创建MyServlet类,添加注解`@WebServlet`

import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet(name = "myServlet", urlPatterns = "/servlet")
    public class MyServlet extends HttpServlet {
    
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            System.out.println("test Servlet");
            doPost(request, response);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.getWriter().write("Hello World!");
            response.flushBuffer();
        }
    }

二、过滤器  
首先同样需要在入口程序中加入配置`@ServletComponentScan`  
其次创建过滤器类MyFilter ,`@WebFilter`中urlPatterns 参数的含义是匹配所有路径。

package com.example.sprintboot.servlet.util.filter;
    
    
    import javax.servlet.*;
    import javax.servlet.annotation.WebFilter;
    import java.io.IOException;
    
    @WebFilter(urlPatterns = "/*")
    public class MyFilter implements Filter {
    
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            System.out.println("init Myfilter");
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            System.out.println("do Myfilter ");
            filterChain.doFilter(servletRequest, servletResponse);
        }
    
        @Override
        public void destroy() {
            System.out.println("destroy Myfilter ");
        }
    }

如果需要配置多个过滤器时，采用注解配置的过滤器无法设置过滤器的优先级，想要配置过滤器的顺序需要采用另一种配置方式。  
首先MyFilter 类中去掉注解  
其次在入口类中添加接口ServletContextInitializer ，重写方法onStartup，便可以配置过滤器，以添加的先后顺序为过滤器的顺序。

package com.example.sprintboot.servlet;
    
    import com.example.sprintboot.servlet.util.filter.MyFilter;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.web.servlet.ServletComponentScan;
    import org.springframework.boot.web.servlet.ServletContextInitializer;
    
    import javax.servlet.DispatcherType;
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import java.util.EnumSet;
    
    @SpringBootApplication
    public class ServletApplication implements ServletContextInitializer {
    
        @Override
        public void onStartup(ServletContext servletContext) throws ServletException {
    
            servletContext.addFilter("myFilter", new MyFilter())
                    .addMappingForUrlPatterns(EnumSet.of(DispatcherType.REQUEST), true, "/*");
    
    
        }
    
        public static void main(String[] args) {
            SpringApplication.run(ServletApplication.class, args);
        }
    }

同样可以使用这种方法配置servlet及监听器（去掉MyServlet与MyListener的注解）

servletContext.addServlet("myServlet", new MyServlet()).addMapping("/roncoo");
    
    servletContext.addListener(new MyListener());

三、监听器  
首先同样需要在入口程序中加入配置`@ServletComponentScan`  
其次创建过滤器类MyFilter ,添加注解`@WebListener`

package com.example.sprintboot.servlet.util.listerner;
    
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    import javax.servlet.annotation.WebListener;
    
    @WebListener
    public class MyListerner implements ServletContextListener {
        @Override
        public void contextInitialized(ServletContextEvent servletContextEvent) {
            System.out.println("init Listerner");
        }
    
        @Override
        public void contextDestroyed(ServletContextEvent servletContextEvent) {
            System.out.println("init destroyListerner");
        }
    }

四、拦截器  
拦截器与servlet无关,无需在入口程序中添加注解`@ServletComponentScan`  
首先第一步创建拦截器类,MyInterceptor 继承接口HandlerInterceptor

package com.example.sprintboot.servlet.util.Interceptor;
    
    import org.springframework.web.servlet.HandlerInterceptor;
    import org.springframework.web.servlet.ModelAndView;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class MyInterceptor implements HandlerInterceptor {
        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
                throws Exception {
            System.out.println("MyInterceptor1>>>>>>>在请求处理之前被调用调用");
    
            return true;// 只有返回true才会继续向下执行，返回false取消当前请求
        }
    
        @Override
        public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
                               ModelAndView modelAndView) throws Exception {
            System.out.println("MyInterceptor1>>>>>>>请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）");
        }
    
        @Override
        public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
                throws Exception {
            System.out.println("MyInterceptor1>>>>>>>在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）");
        }
    }

第二步配置拦截器到服务中,添加@Configuration的作用是使得该配置类被扫描到，有多个拦截器时使用registry.addInterceptor()方法依次添加，添加顺序即为拦截器被调用的顺序。

package com.example.sprintboot.servlet.util.configuration;
    
    import com.example.sprintboot.servlet.util.Interceptor.MyInterceptor;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
    
    @Configuration
    public class MyWebMvcConfigurerAdapter extends WebMvcConfigurerAdapter {
        @Override
        public void addInterceptors(InterceptorRegistry registry) {
            System.out.println("Configuration 配置成功");
    
            registry.addInterceptor(new MyInterceptor()).addPathPatterns("/web/**");  //对来自/web/** 这个链接来的请求进行拦截
        }
    }

[springBoot]: https://blog.csdn.net/u014296316/article/details/85483174
[70]: /images/20220530/863d52eb639b4ecab0b1534fb88e0791.png