过滤器和拦截器的异同

过滤器（Filter）：当你有一堆东西的时候，你只希望选择符合你要求的某一些东西。定义这些要求的工具，就是过滤器。
拦截器（Interceptor）：在一个流程正在进行的时候，你希望干预它的进展，甚至终止它进行，这是拦截器做的事情。

相同点：都是aop编程思想的体现，可以在程序执行前后做一些操作
不同点：过滤器依赖于servlet容器，拦截器不依赖过滤器的执行由Servlet容器回调完成，而拦截器通常通过动态代理的方式来执行。触发时机不一样，过滤器是在请求进入Tomcat容器后，而进入servlet前进行预处理的；拦截器是在进入servlet之后，而进入controller之前处理的。拦截器可以获取IOC容器中的各个bean，而过滤器就不行，拦截器归Spring管理。

过滤器一

package com.duing.filter;

import javax.servlet.*;
import java.io.IOException;

public class CustomFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println(".............CustomFilter init............");
    }

    @Override
    public void doFilter(ServletRequest servletRequest,
                         ServletResponse servletResponse,
                         FilterChain filterChain)
            throws IOException, ServletException {
        System.out.println(".............CustomFilter doFilter............");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        System.out.println(".............CustomFilter destroy............");
    }
}

过滤器二

package com.duing.filter;


import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@WebFilter(filterName = "customFilter2",urlPatterns = {"/*"})
public class CustomFilter2 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println(".............CustomFilter2 init............");
    }

    @Override
    public void doFilter(ServletRequest servletRequest,
                         ServletResponse servletResponse,
                         FilterChain filterChain)
            throws IOException, ServletException {
        System.out.println(".............CustomFilter2 doFilter............");
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {
        System.out.println(".............CustomFilter2 destroy............");
    }
}

过滤器配置类

FilterConfig

import com.duing.filter.CustomFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;


/**
 * web.xml
 * <filter>
 *     <filter-name>struts2</filter-name>
 *     <filter-class>com.duing.filter.CustomFilter</filter-class>
 * </filter>
 *
 * <filter-mapping>
 *     <filter-name>struts2</filter-name>
 *     <url-pattern>/*</url-pattern>
 * </filter-mapping>
 */
@Configuration
public class FilterConfig {

    @Bean
    public FilterRegistrationBean<CustomFilter> filterRegistrationBean(){
        FilterRegistrationBean<CustomFilter> filterFilterRegistrationBean=
                new FilterRegistrationBean<>();
        filterFilterRegistrationBean.setFilter(new CustomFilter());
        filterFilterRegistrationBean.addUrlPatterns("/*");
//        filterFilterRegistrationBean.setOrder(0); //决定注册的优先级
        return filterFilterRegistrationBean;
    }
}

拦截器

package com.duing.interceptor;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Service;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Service
public class CustomInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request,
                      HttpServletResponse response, Object handler)
            throws Exception {
        System.out.println("...........CustomInterceptor prehandle...........");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request,
                    HttpServletResponse response, Object handler,
                    @Nullable ModelAndView modelAndView) throws Exception {

        System.out.println("...........CustomInterceptor postHandle...........");
    }

    @Override
    public void afterCompletion(HttpServletRequest request,
                                HttpServletResponse response, Object handler,
                                 @Nullable Exception ex) throws Exception {

        System.out.println("...........CustomInterceptor afterCompletion...........");

    }

}

拦截器配置类

import com.duing.interceptor.CustomInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class InterceptorConfig implements WebMvcConfigurer{

    @Autowired
    private CustomInterceptor customInterceptor;


    /**
     * 注册自定义的拦截器，并且定义拦截规则
     * @param registry
     */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(customInterceptor).addPathPatterns("/**");

    }
}

controller

package com.duing.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ServletController {

    @RequestMapping("/servlet")
    public String servlet(){
        System.out.println("ServletController servlet........");
        return "Hello Servlet";
    }
}

springboot启动类

package com.duing;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;

@SpringBootApplication  
@ServletComponentScan   //扫描@WebFilter(filterName = "customFilter2",urlPatterns = {"/*"})过滤器注解
public class ServletApplication {

    public static void main(String[] args) {
        SpringApplication.run(ServletApplication.class, args);
    }

}