2021-09-27

• Filter实现
• • 定义
  • 注册过滤器

过滤器是一个对象，它对资源（servlet 或静态内容）的请求或来自资源的响应执行过滤任务。
过滤器在doFilter方法中执行过滤。 每个过滤器都可以访问一个 FilterConfig 对象，它可以从中获取其初始化参数，
一个对 ServletContext 的引用，它可以使用它来加载过滤任务所需的资源

1、使用 @Configuration 注解添加到过滤器链中，此方式适用于使用第三方的过滤器。将过滤器写到 FilterConfig 类中，如下：

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.ArrayList;
import java.util.List;

@Configuration
public class FilterConfig {

   @Bean
   public FilterRegistrationBean filterLoginBean() {
      FilterRegistrationBean registrationBean = new FilterRegistrationBean();
      String excludeUrl = ".html,.js";
      registrationBean.setFilter(new LoginFilter());
      //设置过滤器拦截请求
      List urls = new ArrayList<>();
      //需要拦截的请求路径
      registrationBean.addUrlPatterns("/*");
      //注册拦截器名称，不定义则为Bean对象name
      registrationBean.setName("loginFilter");
      //此次可以初始化数据传递给其他的filter
      registrationBean.addInitParameter("excludeUrl",excludeUrl);
      //优先级
      registrationBean.setOrder(1);
      return registrationBean;
   }
   //可以定义多个bean
}

2、@Component注解注册filter

@Component
public class LoginFilter implements Filter  {
  @Override
    public void init(FilterConfig filterConfig) throws ServletException
    {
    	//获取FilterConfig传递的数据
    	String excludedUrls = filterConfig.getInitParameter("excludeUrl");
    }
        @Override
    public void destroy() {
    }
    
     @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
            
        HttpServletRequest request = (HttpServletRequest) req;
		HttpServletResponse response = (HttpServletResponse) res;
		//获取url，包括服务器、端口、服务器路径和协议，不包含参数
		StringBuffer url = request.getRequestURL();
		//返回服务器路径
		String servletPath = request.getServletPath();
		
    }

}

3、使用@WebFilter

@WebFilter(urlPatterns = "/*",filterName = "XssFilter")
public class XssFilter implements Filter {

    static Logger log = LoggerFactory.getLogger(XssFilter.class);

    private List urlExclusion =   new linkedList<>();

    @Override
    public void init(javax.servlet.FilterConfig filterConfig) throws ServletException 
    {
    }

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