SpringBoot2.0（过滤器，监听器，拦截器）

一，过滤器
- 1.1，自定义Filter
- 1.2，启动类代码
- 1.2，创建filter类和LoginFilter包
- - 1.2.1，编写loginFilter类过滤器代码
  - 1.2.2，创建二个Controller类
二，监听器
- 2.1，自定义监听器
- 2.2，创建listenter包和MyListenter类
- - 2.2.1，编写MyListenter类监听器代码
三，拦截器
- 3.1，创建自定义拦截器配置类
- 3.2，创建配置包config和配置类MyWebMvcConfigurer
- 3.3，创建拦截器包interceptor和Logininterceptor类
四，按顺序进行拦截，先注册，先被拦截

一，过滤器

1.1，自定义Filter

使用Servlet3.0的注解进行配置
启动类里面增加 @ServletComponentScan ，进行扫描
新建一个Filter类，implements Filter ，并实现对应接口
@WebFilter 标记一个类为Filter，被spring进行扫描
urlPatterns:拦截规则，支持正则
控制chain.doFilter的方法的调用，来实现是否通过放行，
不放行的话，web应用resp.sendRedirect(“/index.html”)
场景：权限控制，用户登录（非前端后端分离场景）等

1.2，启动类代码

package com.demo;import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;@SpringBootApplication
@ServletComponentScan  // 扫描select的注解
public class DemoApplication {public static void main(String[] args) {SpringApplication.run(DemoApplication.class,args);}}

1.2，创建filter类和LoginFilter包

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1.2.1，编写loginFilter类过滤器代码

package com.demo.filter;import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.io.PrintWriter;@WebFilter(urlPatterns = {"/*"})
@Order(Ordered.HIGHEST_PRECEDENCE)    // 设置过滤器的排序,int类型
public class LoginFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("初始化过滤器");}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("doFilter");
//        servletResponse.setCharacterEncoding("UTF-8");// 设置响应的字符编码为UTF-8servletResponse.setCharacterEncoding("UTF-8");// 设置响应的内容类型为text/plain;charset=UTF-8servletResponse.setContentType("text/plain;charset=UTF-8");// 登录过滤器 有两种情况，需要放行// 1，登录请求要放行// 2. 不是登录请求，但是有登录tokenString uri = ((HttpServletRequest)servletRequest).getRequestURI();System.out.println(uri);if (uri.startsWith("/login/")){  // 判断是否以 /login/ 开头// 放行filterChain.doFilter(servletRequest,servletResponse);}else {// 从请求中获取tokenString token = ((HttpServletRequest)servletRequest).getParameter("token");if (token != null && !"".equals(token)){// 其实还需要进行解码，现在是只要有token就放行filterChain.doFilter(servletRequest,servletResponse);}else {PrintWriter pw = servletResponse.getWriter();pw.flush();pw.write("请先登录");pw.close();}}}@Overridepublic void destroy() {System.out.println("销毁过滤器");}
}

1.2.2，创建二个Controller类

看看是不是以login开头的放行

第一个controller类为LoginController

package com.demo.controller;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;@RestController
@RequestMapping("/login")
public class LoginController {@RequestMapping("/doLogin")public Object doLogin(){return "登录接口";}
}

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第二个controller类为HelloController

看看不是以login会不会过滤

package com.demo.controller;import com.demo.bean.Person;
import com.demo.config.BootProperties;
import com.demo.config.SysProperties;
import com.demo.util.ResultUtil;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.env.Environment;
import org.springframework.util.ClassUtils;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;import javax.servlet.http.HttpServletRequest;
import javax.xml.crypto.Data;
import java.io.File;
import java.io.IOException;
import java.util.Date;
import java.util.UUID;@RestController
public class HelloController {@Autowiredprivate BootProperties bootProperties;@RequestMapping("/test6")public Object test6(){return sysProperties.getParam1()+sysProperties.getParam2();}
}
// 整个之前的代码试试

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证明过滤了，试试登录后

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二，监听器

2.1，自定义监听器

自定义Listenter（常用监听器
servletContextListenter，
httpSessionListenter，
HTTPSessionAttributeListenter，
servletRequestListenter）

2.2，创建listenter包和MyListenter类

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2.2.1，编写MyListenter类监听器代码

package com.demo.listener;import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;@WebListener
public class MyListener implements ServletRequestListener {@Overridepublic void requestDestroyed(ServletRequestEvent servletRequestEvent) {System.out.println("请求被销毁");}@Overridepublic void requestInitialized(ServletRequestEvent servletRequestEvent) {System.out.println("请求被初始化创建");}
}

三，拦截器

3.1，创建自定义拦截器配置类

@Configuration
继承WebMvcConfigurationAdapter（SpringBoot2.X之前旧版本）
SpringBoot2.X新版本配置拦截器 implements WebMvcConfigurer

3.2，创建配置包config和配置类MyWebMvcConfigurer

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package com.demo.config;import com.demo.interceptor.Logininterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;@Configuration  // 添加了Configuration的类，我们称之为配置类
public class MyWebMvcConfigurer implements WebMvcConfigurer {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new Logininterceptor()).addPathPatterns("/login/**");WebMvcConfigurer.super.addInterceptors(registry);}
}

3.3，创建拦截器包interceptor和Logininterceptor类

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Logininterceptor类代码

package com.demo.interceptor;import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Logininterceptor implements HandlerInterceptor {// 调用Controller某个方法之前，判断是否要不要处理@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {return false; // false是拦截, true是不拦截}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("postHandle");}@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {System.out.println("afterCompletion");}
}