过滤器

1.工作原理

2.创建Filter

2.1通过注解的方式实现

//创建一个类，实现Filter接口
@WebFilter(urlPatterns = "/myfilter") //urlPatterns表示需要拦截的路径
public class MyFilter implements Filter {@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("---------您已进入过滤器----------");filterChain.doFilter(servletRequest,servletResponse);}
}

//启动类上定义一个过滤器扫描器
@SpringBootApplication
@ServletComponentScan(basePackages = "com.liuhaiyang.springboot.filter")  //filter类的地址
public class SpringbootTest14Application {public static void main(String[] args) {SpringApplication.run(SpringbootTest14Application.class, args);}

2.2 springboot的配置类实现

//写一个过滤器，不使用注解
public class MyFilter implements Filter {@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("---------您已进入过滤器222----------");filterChain.doFilter(servletRequest,servletResponse);}
}

//定义一个配置类，用于设定filter
@Configuration 
public class FilterConfig {@Beanpublic FilterRegistrationBean myFilterRegistrationBean(){FilterRegistrationBean filterRegistrationBean=new FilterRegistrationBean(new MyFilter());//构造函数中传入的是自定义的filter对象//添加过滤路径filterRegistrationBean.addUrlPatterns("/user/*");//拦截路径return filterRegistrationBean;}

如果想要实现重定向可以这么做

@Slf4j
@WebFilter(filterName = "first" , urlPatterns = "/*")
@Order(1)
public class Filter implements javax.servlet.Filter{@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("---------您已进入过滤器---------");HttpServletRequest request= (HttpServletRequest) servletRequest;HttpServletResponse response= (HttpServletResponse) servletResponse;String url = request.getRequestURI();if(url.contains("login")){filterChain.doFilter(servletRequest,servletResponse);log.info("放行！！！");}else{//过滤器触发，进行重定向跳转，跳转到对应的控制器String destination = "/user/error"; // 跳转目标RequestDispatcher dispatcher = request.getRequestDispatcher(destination);dispatcher.forward(request, response);}}
}```