SpringBoot系列——Filter 过滤器

以你之姓@ 2021-10-19 09:56 478阅读 0赞

## 　　前言 ##

本文记录一下在SpringBoot项目中是如何使用Filter过滤器

## 　　代码、测试 ##

Filter过滤器是servlet包下面的东西，因此我们不需要再额外引包

### 　　方法一 ###

直接实现**Filter**接口，并使用**@Component**注解标注为组件自动注入bean

package cn.huanzi.qch.springbootfilter.filter;
    
    import org.springframework.stereotype.Component;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @Component
    public class TestFilter implements Filter {
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
    
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            HttpServletRequest request = (HttpServletRequest) servletRequest;
            HttpServletResponse response = (HttpServletResponse) servletResponse;
    
            System.out.println("TestFilter,"+request.getRequestURI());
    
            //执行
            filterChain.doFilter(servletRequest, servletResponse);
        }
    
        @Override
        public void destroy() {
    
        }
    }

查看日志可以发现，SpringBoot已经帮我们注入了一个filter，拦截路径是/\*，拦截所有，如果我们需要进一步拦截具体的则需要我们自己在代码里控制

![1353055-20190724160708938-936726348.png][]

### 　　方法二 ###

实现Filter接口，用**@WebFilter**注解，指定拦截路径以及一些参数，同时需要在**启动类**使用**@ServletComponentScan**扫描带@WebFilter、@WebServlet、@WebListener并将帮我们注入bean``

请看官网介绍：[https://docs.spring.io/spring-boot/docs/2.1.5.RELEASE/reference/htmlsingle/\#boot-features-embedded-container-servlets-filters-listeners-scanning][https_docs.spring.io_spring-boot_docs_2.1.5.RELEASE_reference_htmlsingle_boot-features-embedded-container-servlets-filters-listeners-scanning]

![1353055-20190724161410617-105739235.png][]

package cn.huanzi.qch.springbootfilter.filter;
    
    import javax.servlet.*;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    //配置拦截路径
    @WebFilter(filterName = "testFilter",urlPatterns = {"/test"})
    public class TestFilter implements Filter {
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
    
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            HttpServletRequest request = (HttpServletRequest) servletRequest;
            HttpServletResponse response = (HttpServletResponse) servletResponse;
    
            System.out.println("TestFilter,"+request.getRequestURI());
    
            //执行
            filterChain.doFilter(servletRequest, servletResponse);
        }
    
        @Override
        public void destroy() {
    
        }
    }

package cn.huanzi.qch.springbootfilter;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.web.servlet.ServletComponentScan;
    
    //自动扫描与当前类的同包以及子包
    @ServletComponentScan
    @SpringBootApplication
    public class SpringbootFilterApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(SpringbootFilterApplication.class, args);
        }
    
    }

查看日志发现，以及帮我们注入了testFilter，拦截路径是/test

![1353055-20190724161654961-357254305.png][]

只指定拦截路径，不设置filterName一样可以注入

//配置拦截路径
    @WebFilter({"/test"})

![1353055-20190724162011592-100950614.png][]

### 　　方法三 ###

当然了，我们也可以既使用**@Component**同时也使用**@WebFilter**

package cn.huanzi.qch.springbootfilter.filter;
    
    import org.springframework.stereotype.Component;
    
    import javax.servlet.*;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    
    //配置拦截路径
    @WebFilter(filterName = "testFilter",urlPatterns = {"/test"})
    @Component
    public class TestFilter implements Filter {
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
    
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            HttpServletRequest request = (HttpServletRequest) servletRequest;
            HttpServletResponse response = (HttpServletResponse) servletResponse;
    
            System.out.println("TestFilter,"+request.getRequestURI());
    
            //执行
            filterChain.doFilter(servletRequest, servletResponse);
        }
    
        @Override
        public void destroy() {
    
        }
    }

但是做会注入两个bean，如果你的@WebFilter没有指定filterName或者指定的名称与类名相同，由于注入两个相同名称的bean，程序启动报错，叫我们修改其中一个的名字，或者启用覆盖bean

![1353055-20190724162834758-1834221605.png][]

这里建议如果你硬要采用第三种方法，最好启用覆盖，因为改名将会注入两个bean，处理逻辑一样但拦截路径不一样，这并不是我们想要的，例如：

![1353055-20190724163237065-758155391.png][]

启用覆盖

#启用覆盖同名bean
    spring.main.allow-bean-definition-overriding=true

![1353055-20190724163414928-2089008365.png][]

PS：这里额外说一点，如果我们采用第三种方法，**@ServletComponentScan**放在**TestFilter**类上**@WebFilter**也会被扫描到，不需要放在启动类，第二种方法如果也这样做就不行，估计是受到了**@Component**注解的影响

//配置拦截路径
    @WebFilter(filterName = "testFilter",urlPatterns = {"/test"})
    @ServletComponentScan
    @Component
    public class TestFilter implements Filter

## 　　后记 ##

Filter过滤器暂时先记录到这，以后再进行补充

## 　　代码开源 ##

代码已经开源、托管到我的GitHub、码云：

GitHub：[https://github.com/huanzi-qch/springBoot][https_github.com_huanzi-qch_springBoot]

码云：[https://gitee.com/huanzi-qch/springBoot][https_gitee.com_huanzi-qch_springBoot]

转载于:https://www.cnblogs.com/huanzi-qch/p/11239167.html

[1353055-20190724160708938-936726348.png]: /images/20211018/69b93ace9cdf4de8a1471cba988448be.png
[https_docs.spring.io_spring-boot_docs_2.1.5.RELEASE_reference_htmlsingle_boot-features-embedded-container-servlets-filters-listeners-scanning]: https://docs.spring.io/spring-boot/docs/2.1.5.RELEASE/reference/htmlsingle/#boot-features-embedded-container-servlets-filters-listeners-scanning
[1353055-20190724161410617-105739235.png]: /images/20211018/938c80a66eaa469d8c5ed7875885530a.png
[1353055-20190724161654961-357254305.png]: /images/20211018/5591e87b862d476aacbd0652b1c1cec4.png
[1353055-20190724162011592-100950614.png]: /images/20211018/3c67d7b34ad24a448fedba19291bd7ee.png
[1353055-20190724162834758-1834221605.png]: /images/20211018/a1ba5a2d3a214348bb0d6783c1a49692.png
[1353055-20190724163237065-758155391.png]: /images/20211018/b2a4a452a92547b7a405e3605fb217bb.png
[1353055-20190724163414928-2089008365.png]: /images/20211018/8979236235894a26974117768f755b2e.png
[https_github.com_huanzi-qch_springBoot]: https://github.com/huanzi-qch/springBoot
[https_gitee.com_huanzi-qch_springBoot]: https://gitee.com/huanzi-qch/springBoot