幾個參數(shù)

order(number) :過濾器的順序
filterName : 過濾器名稱
urlPatterns : 需要過濾的路徑
initParams : 初始化參數(shù)，存于FilterConfig中

注意

• order 越小越先被經(jīng)過，即：通過filter的順序是根據(jù)order從小到大依次通過
• 在doFilter（）方法中，chain.doFilter()前的一般是對request執(zhí)行的過濾操作，chain.doFilter()后面的代碼一般是對response執(zhí)行的操作
• 傳入的路徑參數(shù)沒有 ’/’ 的含義：沒有斜杠表示是相對于當前 Servlet 的路徑

例如：請求路徑為  http://127.0.0.1/fdemo/filter/test  (/fdemo 是上下文)
request.getRequestDispatcher("/page").forward(request,response); // 跳轉(zhuǎn)路徑為 http://127.0.0.1/fdemo/page
request.getRequestDispatcher("page").forward(request,response);  // 跳轉(zhuǎn)路徑為 http://127.0.0.1/fdemo/filter/page

• .forward()方法會直接跳到對應(yīng)的controller，而不會走后面的Filter

Springboot項目中創(chuàng)建一個Filter

import lombok.extern.slf4j.Slf4j;
import org.springframework.core.annotation.Order;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@Order(1)
@WebFilter(filterName = "Filter4", urlPatterns = "/*")
@Slf4j
public class Filter4 implements Filter {
    /**
     * 可以初始化Filter在web.xml里面配置的初始化參數(shù)
     * filter對象只會創(chuàng)建一次，init方法也只會執(zhí)行一次。
     */
    @Override
    public void init(FilterConfig filterConfig) {
        log.info("---過濾器的初始化方法！---");
    }
    /**
     * 主要的業(yè)務(wù)代碼編寫方法
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        String contextPath = request.getContextPath();
        String requestURI = request.getRequestURI();
        StringBuffer requestURL = request.getRequestURL();
        String method = request.getMethod();
        String queryString = request.getQueryString();
        String servletPath = request.getServletPath();
        HttpSession session = request.getSession();
        if ("/index".equals(servletPath)){
            request.getRequestDispatcher("/page").forward(request,response);
        }
        log.info("doFilter 之前");
//        filterChain.doFilter(servletRequest, servletResponse);
        log.info("doFilter 之后");
    }
    /**
     * 在銷毀Filter時自動調(diào)用。
     */
    @Override
    public void destroy() {
        log.info("---銷毀Filter---");
    }
}