SpringBoot 中過濾器的簡介及使用方式

過濾器簡介

• 過濾器依賴Servlet容器，屬於Servlet規范的一部分。
• 在實現上基於Servlet容器的函數回調，可以對幾乎所有請求進行過濾。
• Filter的生命周期由Servlet容器管理。

過濾器執行流程

過濾器配置使用方式一

@Order(1) // 指定過濾器的執行順序
@WebFilter(filterName = "CostTimeFilter", urlPatterns = "/*" , initParams = {
        @WebInitParam(name = "URL", value = "http://localhost:8080")})
public class CostTimeFilter implements Filter {
    private String url;
    /**
     * filter對象只會創建一次，init方法也只會執行一次。
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.url = filterConfig.getInitParameter("URL");
        System.out.println("Filter init...");
    }

    /**
     * 主要的業務代碼編寫方法
     */
    @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...");
    }

    /**
     * 在銷毀Filter時自動調用。
     */
    @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 // 掃描 Servlet 相關的組件
public class SpringBootFilterApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootFilterApplication.class, args);
    }
}

過濾器配置方式二

public class CostTimeFilter implements Filter {
    private String url;
    /**
     * filter對象只會創建一次，init方法也只會執行一次。
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.url = filterConfig.getInitParameter("URL");
        System.out.println("Filter init...");
    }

    /**
     * 主要的業務代碼編寫方法
     */
    @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...");
    }

    /**
     * 在銷毀Filter時自動調用。
     */
    @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;
    }
}