一文详解Java * 与过滤器的使用

流程图

* vs过滤器

* 是SpringMVC的技术

过滤器的Servlet的技术

先过过滤器，过滤器过完才到DispatcherServlet；

* 归属于SpringMVC，只可能拦SpringMVC的东西；

* 说白了就是为了增强，可以在请求前进行增强，也可以在请求后进行增强，但是不一定同时在前后都增强。

区别

SpringMVC技术架构图

项目Demo

项目地址

依赖

<parent>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-parent</artifactId>
       <version>2.2.7.RELEASE</version>
   </parent>

<dependencies>
       <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-web</artifactId>
       </dependency>
   </dependencies>

Interceptor *

package com.test.filtertest.inter;

import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
* *
*
* @author: zhangzengxiu
* @createDate: 2022/4/22
*/
@Component
public class TestInter1 implements HandlerInterceptor {

@Override
   public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
       System.out.println("TestInter1 preHandle...");
       return true;
   }

@Override
   public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
       System.out.println("TestInter1 postHandle...");
   }

@Override
   public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
       System.out.println("TestInter1 afterCompletion...");
   }
}

Interceptor * 要注册

package com.test.filtertest.config;

import com.test.filtertest.inter.TestInter1;
import com.test.filtertest.inter.TestInter2;
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;

/**
* @author zhangzengxiu
* @date 2022/4/22
*/
@Configuration
public class WebConfig implements WebMvcConfigurer {

@Autowired
   private TestInter1 testInter1;

@Autowired
   private TestInter2 testInter2;

@Override
   public void addInterceptors(InterceptorRegistry registry) {
       //默认/** 拦截所有请求
       registry.addInterceptor(testInter1).addPathPatterns("/**");
       registry.addInterceptor(testInter2);
   }
}

拦截顺序

多 * 拦截顺序取决于registry的注册顺序

Filter过滤器

1、多Filter不指定过滤顺序

package com.test.filtertest.filter;

import org.springframework.core.annotation.Order;

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

/**
* @author zhangzengxiu
* @date 2022/4/22
*/
@WebFilter(filterName = "TestFilter1", urlPatterns = "/*")
//@Order(2) //filter这样定义拦截顺序无效，还是会按照类名去拦截
public class TestFilter1 implements Filter {

@Override
   public void init(FilterConfig filterConfig) throws ServletException {

}

@Override
   public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
       System.out.println("TestFilter1 filter before ...");
       filterChain.doFilter(servletRequest, servletResponse);
       System.out.println("TestFilter1 filter after ...");
   }

@Override
   public void destroy() {

}
}

加了@WebFilter注解的过滤器要生效，需要在启动类上加一个注解@ServletComponentScan

2、多Filter指定过滤顺序

如果要设置过滤顺序的话，在Filter上添加@Order 不会生效，还是会默认根据Filter过滤器的类名去进行过滤。

如果想要指定拦截顺序，需要添加一个配置类，通过设置Order的值去设置过滤顺序，Order数值越小优先级越高

package com.test.config;

import com.test.filter.TestFilter1;
import com.test.filter.TestFilter2;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.servlet.Filter;

/**
* filter过滤器配置
*
* @author: zhangzengxiu
* @createDate: 2022/4/24
*/
@Configuration
public class FilterConfig {

@Bean
   public FilterRegistrationBean testFilter1() {
       FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
       Filter testFilter1 = new TestFilter1();
       filterRegistrationBean.setFilter(testFilter1);
       filterRegistrationBean.addUrlPatterns("/*");
       filterRegistrationBean.setName("testFilter1");
       filterRegistrationBean.setOrder(2);//指定过滤顺序，数值越小优先级越高
       return filterRegistrationBean;
   }

@Bean
   public FilterRegistrationBean testFilter2() {
       FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
       Filter testFilter2 = new TestFilter2();
       filterRegistrationBean.setFilter(testFilter2);
       filterRegistrationBean.setName("testFilter2");
       filterRegistrationBean.addUrlPatterns("/*");
       filterRegistrationBean.setOrder(1);//指定过滤顺序，数值越小优先级越高
       return filterRegistrationBean;
   }
}

1、同时原本Filter过滤器上的@WebFilter(filterName = &ldquo;TestFilter1&rdquo;, urlPatterns = &ldquo;/*&rdquo;)

这个注解最好去掉，否则bean重复会报错，要么bean名称不要重复，换个名称。但是不去掉的话@ServletComponentScan也要被保留，最好统一格式，只使用config配置。

2、启动类上的@ServletComponentScan 注解也不需要了，可以去掉了，因为不用扫描@WebFilter注解了。但是如果@WebFilter还保留了，那么就不能去掉了。不然加了@WebFilter的过滤器就不会生效了，因为没扫到。

来源：https://blog.csdn.net/zhangzengxiu/article/details/124357436