Filter生命周期

過濾器要重寫3個(gè)方法

init(FilterConfig filterConfig)：?jiǎn)?dòng)項(xiàng)目的時(shí)候執(zhí)行

doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)：資源攔截的時(shí)候執(zhí)行

destroy()：正常關(guān)閉項(xiàng)目的時(shí)候執(zhí)行

來(lái)看下面例子，準(zhǔn)備2個(gè)Filter過濾器，都攔截所有的路徑

過濾器demo2代碼

package com.lingaolu.filter; 
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException; 
/**
 * @author 林高祿
 * @create 2020-08-04-9:42
 */
@WebFilter("/*")    
public class Demo2 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("demo2過濾器初始化了......");
    } 
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("demo2過濾器進(jìn)來(lái)了......");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("demo2過濾回來(lái)了......");
    } 
    @Override
    public void destroy() {
        System.out.println("demo2過濾器摧毀了......");
    }
}

過濾器demo3代碼

package com.lingaolu.filter; 
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException; 
/**
 * @author 林高祿
 * @create 2020-08-04-9:42
 */
@WebFilter("/*")
public class Demo3 implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("demo3過濾器初始化了......");
    } 
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("demo3過濾器進(jìn)來(lái)了......");
        filterChain.doFilter(servletRequest,servletResponse);
        System.out.println("demo3過濾回來(lái)了......");
    } 
    @Override
    public void destroy() {
        System.out.println("demo3過濾器摧毀了......");
    }
}

index.jsp代碼 ,里面學(xué)了一句輸出語(yǔ)句

啟動(dòng)項(xiàng)目，執(zhí)行了init方法，且每個(gè)過濾器的init都只執(zhí)行一次

訪問index.jsp，每次訪問都執(zhí)行，并且先執(zhí)行的過濾器，最后回來(lái)，有點(diǎn)先進(jìn)后出的感覺

正常關(guān)閉項(xiàng)目，每個(gè)過濾器的destrpy方法都只執(zhí)行一次

通過上述相信大家對(duì)Filter生命周期已經(jīng)有所了解，大家如果想學(xué)習(xí)更多相關(guān)知識(shí)，可以來(lái)關(guān)注一下動(dòng)力節(jié)點(diǎn)的Java在線學(xué)習(xí)，里面的課程內(nèi)容豐富，細(xì)致全面，從入門到精通，適合沒有基礎(chǔ)的小伙伴學(xué)習(xí)，希望對(duì)大家能夠有所幫助。