springBoot的过滤器，监听器，拦截器
概述
在开发中，我们经常要考虑一些问题，对敏感词进行过滤，用户是否已经登录，是否需要对他的请求进行拦截，或者领导问现在在线人数有多少人？我们如何实现这些功能哪
@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("===========拦截器初始化==========");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
servletRequest.setCharacterEncoding("utf-8");
servletResponse.setCharacterEncoding("utf-8");
log.info("doFilter请求处理");
}
@Override
public void destroy() {
log.info("fifter销毁");
}
}
在application类中添加@ServletComponentScan注解
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);
}
}
运行结果
（笔误，应该是过滤器初始化）过滤器已经生效，但若有多个过滤器，无法指定执行顺序，我们可以通过Java类的名称，从A-L，按顺序执行。但这种方式毕竟不大靠谱，所以，有第二种写法，它提供setOrder函数，为filter设置排序值。
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("我执行了。。。。。。。");
registration.setFilter(new CustomFilter());
registration.addUrlPatterns("/*");
registration.setOrder(1);
return registration; } }
我们尝试写个demo，验证一下过滤器是否执行。
用户登录对象
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;
}
登录控制
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 "登录成功";
}
return "密码错误，登录失败";
}
@RequestMapping(value = "test",method = RequestMethod.GET)
public String test()
{
return "test接口";
}
}
过滤器
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("===========过滤器初始化==========");
}
@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("登录成功");
}else {
if (session != null && session.getAttribute("user") != null)
{
filterChain.doFilter(servletRequest,servletResponse);
}else {
System.err.printf("暂时未登录");
}
}
log.info("doFilter请求处理");
}
public boolean isNeedFilter(String uri)
{
for (String include:includes)
{
if (include.equals(uri))
{
return false;
}
}
return true;
}
@Override
public void destroy() {
log.info("fifter销毁");
}
}
过滤器配置
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("我执行了。。。。。。。");
registration.setFilter(new CustomFilter());
registration.addUrlPatterns("/*");
return registration;
}
}
运行测试。。访问 127.0.0.1/test 控制台
访问 http://127.0.0.1:8080/login?user=admin&pwd=admin，可以看到登录成功
在次访问 127.0.0.1/test 页面显示
所以，我们的过滤器成功过滤未登录的用户
监听器
正在你为自己会了过滤用户自鸣得意时，你的组长过来了，小明，你看下我们平台的在线用户有多少人。如果不知道监听器童鞋，是否会在登录接口处每次登录成功都+1，然而这种统计结果是不准确的，因为用户如果反复登录退出，那这个在值就远远大于实际值，最后就面临着，加班在加班的悲惨下场。
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("创建session,统计在线人数");
online ++;
}
@Override
public void sessionDestroyed(HttpSessionEvent sessionEvent)
{
System.out.println("session已经销毁");
}
}
配置监听器配置,在刚才的WebFilterConfig.java添加
@Bean
public ServletListenerRegistrationBean listenerRegistrationBean()
{
ServletListenerRegistrationBean srb = new ServletListenerRegistrationBean();
srb.setListener(new CustomLister());
System.out.println("");
return srb;
}
添加一个访问在线人数的接口
@RequestMapping(value = "onLinePerson",method = RequestMethod.GET)
public String onLinePerson()
{
StringBuffer stringBuffer = new StringBuffer("");
stringBuffer.append(" 在线人数 ");
stringBuffer.append(CustomLister.online);
stringBuffer.append(" 个人 ");
return stringBuffer.toString();
}
访问127.0.0.1/onLinePerson,发现被拦截器拦截了，我们先登录。在查看接口
换个浏览器，调用下login接口，在查看
拦截器
拦截器，个人理解，在web上有些像是过滤器的补充，它能更精确的控制拦截哪些函数或者字段，在拦截之前或之后做一些操作。我们现在做一个敏感词的拦截，其实这个操作放在过滤器操作也是可以的，但lz因为刚才把拦截用户的操作放在过滤器了，在大规模更改，lz觉得没必要，因为都是大同小异。
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("=======拦截器被调用=====");
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 则中断请求");
return true;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
{
log.info("请求后调用");
}
@Override
public void afterCompletion(HttpServletRequest request,HttpServletResponse response,Object handler,Exception e)
{
log.info("视图渲染完回调");
}
}
配置拦截
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("我执行了。。。。。。。");
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)
{
/*拦截规则*/
registry.addInterceptor(new CustomInterceptor()).addPathPatterns("/*");
}
}
现在测试访问127.0.0.1/seqing，被过滤，要求先登录。我们调用登录接口后，再次调用，发现被拦截了
看下日志调用，可以发现，拦截器是在访问接口前被调用的
过滤器，拦截器区别
这里主要说下拦截器和过滤器的区别和使用场景，通过demo可以发现，它们都能实现权限的检查，日志记录这些功能，主要说下它们的区别
- 过滤器和拦截器触发的时机是不同的，在进入servlet之前，过滤器就进行预处理了。而拦截器是在调用Controller之前才触发执行，过滤器的范围较广，对所有的请求都起作用，而拦截起只 对action起作用
2.拦截器可以获取IOC容器的各个bean，而过滤器就不行。因为拦截器是spring提供管理的，也因此拦截器可以使用spring的任何资源。
3.拦截器是利用Java反射机制实现，过滤器是函数的回调。因此实现方式是不同的。
三者使用场景
监听器：常用统计在线用户，统计网站的访问量，记录用户的访问路径
过滤器：过滤敏感词，权限访问控制
拦截器：权限验证，判断用户是否登录等
