Springboot 2.x 使用过滤器(Filter) ,拦截器(Intercepter),监听器(Listener)

spring 执行过程时 过滤器先执行，拦截器后执行

1. 过滤器 Filter 的使用。

package cn.waimaolang.demo.middleware;

import cn.waimaolang.demo.utils.HttpResultUtils;
import com.alibaba.fastjson.JSON;
import org.springframework.beans.factory.annotation.Autowired;

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

/**
 * @title 过滤器 根据 urlPatterns 的路径 进行过滤请求
 */
@WebFilter(urlPatterns = {"/home/*"},filterName = "IndexFilter")
public class IndexFilter implements Filter
{
    @Autowired
    HttpResultUtils httpResultUtils;
    /**
     * 框架启动的时候执行
     * 容器加载的时候调用
     */
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("init IndexMiddleware");
    }

    /**
     * 请求被拦截的时候进行调用
     * @param servletRequest
     * @param servletResponse
     * @param filterChain
     * @throws IOException
     * @throws ServletException
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        request.setAttribute("name","wangjun");
        if(true){
            System.out.println("我是过滤器 xxx");
            // 允许继续执行 -> 走控制器
            filterChain.doFilter(servletRequest,servletResponse);
        }else{
            // 返回错误 ,禁止进入控制器
            response.setContentType("application/json;charset=utf-8");//指定返回的格式为JSON格式
            response.setCharacterEncoding("UTF-8");
            PrintWriter out = response.getWriter();
            String json = JSON.toJSONString(httpResultUtils.fail("过滤器阻止你进入xxx"));
            out.write(json);
            out.close();
        }
    }

    /**
     * 容器被销毁的时候被调用
     */
    @Override
    public void destroy() {
        System.out.println("destroy loginFilter");
    }
}

2. 拦截器的使用
   (两步 1.自定义一个Interceptor 2. 注册）

// 定义一个拦截器
package cn.waimaolang.demo.middleware;

import cn.waimaolang.demo.utils.HttpResultUtils;
import com.alibaba.fastjson.JSON;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;

/**
 * 拦截器
 */
public class IndexIntercepter implements HandlerInterceptor
{

    @Autowired
    HttpResultUtils httpResultUtils;

    /**
     * 进入controller方法之前执行
     */
    @Override
    public boolean preHandle(
        HttpServletRequest request,
        HttpServletResponse response,
        Object handler
    ) throws Exception {

       // 权限验证
        String Secret = request.getHeader("Secret");
        if( StringUtils.isEmpty(Secret) || !Secret.equals("xxxxx")){
            // 权限验证失败
            response.setContentType("application/json; charset=UTF-8");
            response.setCharacterEncoding("UTF-8");
            response.setStatus(403);
            PrintWriter out = response.getWriter();// 这一句一定要在前面三句的后面，否则会导致设置ContentType无效
            out.write(JSONObject.toJSONString(new ApiResultResponse(403,"禁止访问，退出登陆")));
            out.close();
            return false;// 权限验证失败，不允许进入控制器
        }
        
        return true; // 进入控制器
    }

    /**
     * 调用完controller之后，视图渲染之前
     */
    @Override
    public void postHandle(
        HttpServletRequest request,
        HttpServletResponse response,
        Object handler,
        ModelAndView modelAndView
    ) throws Exception {
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    /**
     * 一个请求完成之后，通常用于资源清理
     */
    @Override
    public void afterCompletion(
        HttpServletRequest request,
        HttpServletResponse response,
        Object handler,
        Exception ex
    ) throws Exception {
        System.out.println("执行完成 xxxx....");
        HandlerInterceptor.super.afterCompletion(request,response,handler,ex);
    }
}

//注册拦截器

package cn.waimaolang.demo.configura;

import cn.waimaolang.demo.middleware.IndexIntercepter;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * web mvc 模式的 拦截器配置
 */
@Configuration
public class WebMvcConfiguration implements WebMvcConfigurer
{
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //注册多个Interceptor  注意路径的写法
        registry.addInterceptor(new IndexIntercepter()).addPathPatterns("/home/*");
        //registry.addInterceptor(new TwoIntercepter()).addPathPatterns("/api2/*/**");
        //注册某个拦截器的时候，同时排除某些不拦截的路径
        //registry.addInterceptor(new TwoIntercepter()).addPathPatterns("/api2/*/**").excludePathPatterns("/api2/xxx/**");
        WebMvcConfigurer.super.addInterceptors(registry);
    }
}

3.springboot 监听器教程
http://note.youdao.com/noteshare?id=c5df28a39ba57038089a20aad5011369&sub=ACDF29C77E04421298903C2BE6C7E822