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SpringBoot系列——Filter 过滤器

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12/02
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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

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 

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

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"})

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() {

    }

}
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);

    }

}

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

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：

启用覆盖 

#启用覆盖同名bean

spring.main.allow-bean-definition-overriding=true

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

码云：https://gitee.com/huanzi-qch/springBoot

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