Java中Filter的使用

一、概述

二、Spring使用

web.xml文件中加入过滤器的代理类，targetBeanName 的值为过滤器的id值。也就是@Component("authFilter") 中的authFilter。

	<!-- 统一认证过滤器的代理 -->
	<filter>
		<filter-name>DelegatingFilterProxy</filter-name>
		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
		<init-param>
			<param-name>targetBeanName</param-name>
			<param-value>authFilter</param-value>
		</init-param>
		<init-param>
			<param-name>targetFilterLifecycle</param-name>
			<param-value>true</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>DelegatingFilterProxy</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>

@Component() 如果不带参数，默认值为类名首字母小写。

/**
 * 统一认证过滤器
 */
@Component("authFilter")
public class AuthFilter implements Filter {
    
    
    protected static final Logger logger = LoggerFactory.getLogger(AuthFilter.class);
 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
    
    
 
        HttpServletRequest httpRequest = (HttpServletRequest)request;
        HttpServletResponse httpResponse = (HttpServletResponse)response;
        HttpSession session = httpRequest.getSession();
    }
}

三、SpringBoot使用

1、方法一

@WebFilter(filterName = "dataFilter", urlPatterns = "/api/*")
@Order(1)
public class DataFilter implements Filter {
    
    
    @Override
    public void init(FilterConfig filterConfig) {
    
    
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    
    
        chain.doFilter(request, response);
    }

    @Override
    public void destroy() {
    
    
    }
}

在启动类上添加@ServletComponentScan注解

//@ServletComponentScan({"com.scy.frame", "com.scy.app"})
@ServletComponentScan
@SpringBootApplication
public class Application {
    
    
    public static void main(String[] args) {
    
    
        SpringApplication.run(VideoScreenApplication.class, args);
    }
}

@ServletComponentScan作用
SpringBootApplication 上使用@ServletComponentScan 注解后
Servlet可以直接通过@WebServlet注解自动注册
Filter可以直接通过@WebFilter注解自动注册
Listener可以直接通过@WebListener 注解自动注册

2、方法二

不使用@WebFilter方式声明过滤器，使用FilterRegistrationBean在配置类中注入Filter

@Configuration
public class FilterConfiguration {
    
    
    @Bean
    public FilterRegistrationBean dataFilter(){
    
    
        FilterRegistrationBean bean = new FilterRegistrationBean();
        bean.setFilter(new DataFilter());
        bean.setUrlPatterns(Arrays.asList("/api/*"));
        bean.setOrder(6);//优先级，越低越优先
        return bean;
    }
}

3、方法三（有问题）

不再启动类添加@ServletComponentScan注解，使用 @Component 或 @Configuration 导致urlPatterns指定的拦截路径无法生效，出现拦截所有接口情况。

@Component 
@WebFilter(filterName = "dataFilter", urlPatterns = "/api/*")
@Order(1)
public class DataFilter implements Filter {
    
    
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    
    
        chain.doFilter(request, response);
    }
}