springboot如何使用过滤器（SpringBoot系列Filter）

　　本文记录一下在SpringBoot项目中是如何使用Filter过滤器

　　Filter过滤器是servlet包下面的东西，因此我们不需要再额外引包

　　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

　　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"})

　　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

　　Filter过滤器暂时先记录到这，以后再进行补充

　　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

作者：huanzi-qch

出处：https://www.cnblogs.com/huanzi-qch

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