springBoot的過濾器，監聽器，攔截器

農碼關山北發表於2019-07-31
Spring Boot過濾器

概述

　　在開發中，我們經常要考慮一些問題，對敏感詞進行過濾，使用者是否已經登入，是否需要對他的請求進行攔截，或者領導問現在線上人數有多少人？我們如何實現這些功能哪

 @WebFilter

package com.xmlxy.firstspringbootproject;


import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;
@WebFilter(filterName = "customFilter",urlPatterns = "/*")
public class CustomFilter implements Filter {

    private static final Logger log = LoggerFactory.getLogger(CustomFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("===========攔截器初始化==========");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        log.info("doFilter請求處理");
    }

    @Override
    public void destroy() {
        log.info("fifter銷燬");
    }
}

在application類中新增@ServletComponentScan註解

package com;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.context.annotation.PropertySource;

@SpringBootApplication
@ServletComponentScan
@PropertySource(value = "classpath:jdbc.properties",encoding = "utf-8")
public class FirstSpringbootProjectApplication {

    public static void main(String[] args) {
        SpringApplication.run(FirstSpringbootProjectApplication.class, args);
    }

}

執行結果

（筆誤，應該是過濾器初始化）過濾器已經生效，但若有多個過濾器，無法指定執行順序，我們可以通過Java類的名稱，從A-L，按順序執行。但這種方式畢竟不大靠譜，所以，有第二種寫法，它提供setOrder函式，為filter設定排序值。

package com.xmlxy.service;

import com.xmlxy.firstspringbootproject.CustomFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class WebFilterConfig
{
    @Bean
    public FilterRegistrationBean someFilterRegistration1()
    {
        FilterRegistrationBean registration = new FilterRegistrationBean<>();
        System.out.println("我執行了。。。。。。。");
        registration.setFilter(new CustomFilter());
        registration.addUrlPatterns("/*");
　　　　 registration.setOrder(1);
　　　　 return registration; } }

我們嘗試寫個demo，驗證一下過濾器是否執行。

使用者登入物件

User.java

package com.xmlxy.bean;

import lombok.Data;
import org.springframework.stereotype.Component;

@Data
@Component
public class User {
    private String user;
    private String pwd;
}

登入控制

LoginController.java

package com.xmlxy.firstspringbootproject;

import com.xmlxy.bean.User;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

@RestController
public class LoginController {

    @RequestMapping(value = "login",method = RequestMethod.GET)
    public String login(HttpServletRequest request)
    {
        String user = request.getParameter("user");
        String pwd = request.getParameter("pwd");
        HttpSession session = request.getSession();
        if ("admin".equals(user) && "admin".equals(pwd))
        {
            User user1 = new User();
            user1.setUser(user);
            user1.setPwd(pwd);
            session.setAttribute("user",user1);
            return "登入成功";
        }
        return "密碼錯誤，登入失敗";
    }
　　@RequestMapping(value = "test",method = RequestMethod.GET)
　　public String test()
　　{
    　　return "test介面";
　　}
}

過濾器

CustomFilter.java

package com.xmlxy.firstspringbootproject;


import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

    private static final Logger log = LoggerFactory.getLogger(CustomFilter.class);

    String includes[] = {"/login","register"};

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        log.info("===========過濾器初始化==========");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
    {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        HttpSession session = request.getSession(false);
        String uri = request.getRequestURI();
        boolean flag = isNeedFilter(uri);
        if (!flag)
        {
            filterChain.doFilter(servletRequest,servletResponse);
            System.err.printf("登入成功");
        }else {
            if (session != null && session.getAttribute("user") != null)
            {
                filterChain.doFilter(servletRequest,servletResponse);
            }else {
                System.err.printf("暫時未登入");
            }
        }

        log.info("doFilter請求處理");
    }
    public boolean isNeedFilter(String uri)
    {
        for (String include:includes)
        {
            if (include.equals(uri))
            {
                return false;
            }
        }
        return true;
    }
    @Override
    public void destroy() {
        log.info("fifter銷燬");
    }
}

過濾器配置

WebFilterConfig

package com.xmlxy.service;

import com.xmlxy.firstspringbootproject.CustomFilter;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class WebFilterConfig
{
    @Bean
    public FilterRegistrationBean someFilterRegistration1()
    {
        FilterRegistrationBean registration = new FilterRegistrationBean<>();
        System.out.println("我執行了。。。。。。。");
        registration.setFilter(new CustomFilter());
        registration.addUrlPatterns("/*");
        return registration;
    }
}

 執行測試。。訪問 127.0.0.1/test  控制檯

訪問  http://127.0.0.1:8080/login?user=admin&pwd=admin，可以看到登入成功

在次訪問 127.0.0.1/test 頁面顯示

所以，我們的過濾器成功過濾未登入的使用者

監聽器

正在你為自己會了過濾使用者自鳴得意時，你的組長過來了，小明，你看下我們平臺的線上使用者有多少人。如果不知道監聽器童鞋，是否會在登入介面處每次登入成功都+1，然而這種統計結果是不準確的，因為使用者如果反覆登入退出，那這個在值就遠遠大於實際值，最後就面臨著，加班在加班的悲慘下場。

CustomLister.java

package com.xmlxy.firstspringbootproject;


import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

@WebFilter
public class CustomLister implements HttpSessionListener
{
    public static int online = 0;

    @Override
    public void sessionCreated(HttpSessionEvent sessionEvent)
    {
        System.out.println("建立session,統計線上人數");
        online ++;
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent sessionEvent)
    {
        System.out.println("session已經銷燬");
    }
}

配置監聽器配置,在剛才的WebFilterConfig.java新增

@Bean
    public ServletListenerRegistrationBean listenerRegistrationBean()
    {
        ServletListenerRegistrationBean srb = new ServletListenerRegistrationBean();
        srb.setListener(new CustomLister());
        System.out.println("");
        return srb;
    }

新增一個訪問線上人數的介面

@RequestMapping(value = "onLinePerson",method = RequestMethod.GET)
    public String onLinePerson()
    {
        StringBuffer stringBuffer = new StringBuffer("");
        stringBuffer.append(" 線上人數 ");
        stringBuffer.append(CustomLister.online);
        stringBuffer.append(" 個人 ");
        return stringBuffer.toString();
    }

訪問127.0.0.1/onLinePerson,發現被攔截器攔截了，我們先登入。在檢視介面

換個瀏覽器，呼叫下login介面，在檢視

攔截器

攔截器，個人理解，在web上有些像是過濾器的補充，它能更精確的控制攔截哪些函式或者欄位，在攔截之前或之後做一些操作。我們現在做一個敏感詞的攔截，其實這個操作放在過濾器操作也是可以的，但lz因為剛才把攔截使用者的操作放在過濾器了，在大規模更改，lz覺得沒必要，因為都是大同小異。

CustomInterceptor.java

package com.xmlxy.firstspringbootproject;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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;

public class CustomInterceptor implements HandlerInterceptor
{
    private static final Logger log = LoggerFactory.getLogger(CustomInterceptor.class);
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response,Object handler) throws Exception {
        log.info("=======攔截器被呼叫=====");
        String url = request.getRequestURI();
        if (url != null && url.indexOf("seqing") != -1)
        {
            PrintWriter printWriter = response.getWriter();
            printWriter.write("ming gan ci");
            return false;
        }
        log.info("返回false 則中斷請求");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
    {
        log.info("請求後呼叫");
    }

    @Override
    public void afterCompletion(HttpServletRequest request,HttpServletResponse response,Object handler,Exception e)
    {
        log.info("檢視渲染完回撥");
    }
}

配置攔截

package com.xmlxy.service;

import com.xmlxy.firstspringbootproject.CustomFilter;
import com.xmlxy.firstspringbootproject.CustomInterceptor;
import com.xmlxy.firstspringbootproject.CustomLister;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebFilterConfig implements WebMvcConfigurer
{
    @Bean
    public FilterRegistrationBean someFilterRegistration1()
    {
        FilterRegistrationBean registration = new FilterRegistrationBean<>();
        System.out.println("我執行了。。。。。。。");
        registration.setFilter(new CustomFilter());
        registration.addUrlPatterns("/*");
        return registration;
    }

    @Bean
    public ServletListenerRegistrationBean listenerRegistrationBean()
    {
        ServletListenerRegistrationBean srb = new ServletListenerRegistrationBean();
        srb.setListener(new CustomLister());
        return srb;
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry)
    {
        /*攔截規則*/
        registry.addInterceptor(new CustomInterceptor()).addPathPatterns("/*");
    }

}

現在測試訪問127.0.0.1/seqing，被過濾，要求先登入。我們呼叫登入介面後，再次呼叫，發現被攔截了

看下日誌呼叫，可以發現，攔截器是在訪問介面前被呼叫的

過濾器，攔截器區別

這裡主要說下攔截器和過濾器的區別和使用場景，通過demo可以發現，它們都能實現許可權的檢查，日誌記錄這些功能，主要說下它們的區別

  1. 過濾器和攔截器觸發的時機是不同的，在進入servlet之前，過濾器就進行預處理了。而攔截器是在呼叫Controller之前才觸發執行，過濾器的範圍較廣，對所有的請求都起作用，而攔截起只 對action起作用

　　2.攔截器可以獲取IOC容器的各個bean，而過濾器就不行。因為攔截器是spring提供管理的，也因此攔截器可以使用spring的任何資源。

　　3.攔截器是利用Java反射機制實現，過濾器是函式的回撥。因此實現方式是不同的。

三者使用場景

　　監聽器：常用統計線上使用者，統計網站的訪問量，記錄使用者的訪問路徑

　　過濾器：過濾敏感詞，許可權訪問控制

　　攔截器：許可權驗證，判斷使用者是否登入等

 

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