SpringBoot 中过滤器的简介及使用方式

过滤器简介

• 过滤器依赖Servlet容器，属于Servlet规范的一部分。
• 在实现上基于Servlet容器的函数回调，可以对几乎所有请求进行过滤。
• Filter的生命周期由Servlet容器管理。

过滤器执行流程

过滤器配置使用方式一

@Order(1) // 指定过滤器的执行顺序
@WebFilter(filterName = "CostTimeFilter", urlPatterns = "/*" , initParams = {
        @WebInitParam(name = "URL", value = "http://localhost:8080")})
public class CostTimeFilter implements Filter {
    private String url;
    /**
     * filter对象只会创建一次，init方法也只会执行一次。
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.url = filterConfig.getInitParameter("URL");
        System.out.println("Filter init...");
    }

    /**
     * 主要的业务代码编写方法
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    	long start = System.currentTimeMillis();
        System.out.println(start + " Filter doFilter before...");
        filterChain.doFilter(servletRequest, servletResponse);
    	long end = System.currentTimeMillis();
        System.out.println(end + "Filter doFilter after...");
    }

    /**
     * 在销毁Filter时自动调用。
     */
    @Override
    public void destroy() {
        System.out.println("Filter destroy...");
    }
}

@RestController
public class IndexContoller {
    @RequestMapping("/query")
    public void query() throws Exception {
        System.out.println("IndexContoller query...");
    }
}

@SpringBootApplication
@ServletComponentScan // 扫描 Servlet 相关的组件
public class SpringBootFilterApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootFilterApplication.class, args);
    }
}

过滤器配置方式二

public class CostTimeFilter implements Filter {
    private String url;
    /**
     * filter对象只会创建一次，init方法也只会执行一次。
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.url = filterConfig.getInitParameter("URL");
        System.out.println("Filter init...");
    }

    /**
     * 主要的业务代码编写方法
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    	long start = System.currentTimeMillis();
        System.out.println(start + " Filter doFilter before...");
        filterChain.doFilter(servletRequest, servletResponse);
    	long end = System.currentTimeMillis();
        System.out.println(end + "Filter doFilter after...");
    }

    /**
     * 在销毁Filter时自动调用。
     */
    @Override
    public void destroy() {
        System.out.println("Filter destroy...");
    }
}

@Configuration
public class FilterConfig {
    @Bean
    public FilterRegistrationBean registFilter() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(new CostTimeFilter());
        registration.addUrlPatterns("/*");
        registration.setName("CostTimeFilter");
        registration.setOrder(1);
        return registration;
    }
}