The use of Filter in Java

I. Overview

Second, the use of Spring

web.xmlThe proxy class of the filter is added in the file, targetBeanNameand the value is the value of the filter id. That is @Component("authFilter")in 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()If there is no parameter, the default value is the first letter of the class name in lowercase.

/**
 * 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();
    }
}

3. Use of SpringBoot

1. Method 1

@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() {
    
    
    }
}

@ServletComponentScanAdd annotations to the startup class

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

@ServletComponentScan works
on SpringBootApplication. After using the @ServletComponentScan annotation on SpringBootApplication,
the Servlet can be automatically registered directly through the @WebServlet annotation.
The Filter can be automatically registered directly through the @WebFilter annotation.
The Listener can be automatically registered directly through the @WebListener annotation.

2. Method 2

Do not use @WebFilterthe way to declare the filter, use FilterRegistrationBeanthe filter to inject in the configuration class

@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. Method 3 (problems)

Do not add annotations to the startup class anymore @ServletComponentScan, use @Componentor @Configurationcause urlPatternsthe specified interception path to fail to take effect, and all interfaces will be intercepted.

@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);
    }
}