=================6、SpringBoot攔截器實戰和 Servlet3.0自定義Filter、Listener ============

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1、深入SpringBoot2.x過濾器Filter和使用Servlet3.0配置自定義Filter實戰(核心知識)
簡介:講解SpringBoot里面Filter講解和使用Servlet3.0配置自定義Filter實戰

filter簡單理解：人--->檢票員（filter）---> 景點

1、SpringBoot啟動默認加載的Filter
characterEncodingFilter
hiddenHttpMethodFilter
httpPutFormContentFilter
requestContextFilter

2、Filter優先級

Ordered.HIGHEST_PRECEDENCE
Ordered.LOWEST_PRECEDENCE

低位值意味著更高的優先級 Higher values are interpreted as lower priority
自定義Filter，避免和默認的Filter優先級一樣，不然會沖突

注冊Filter的bean FilterRegistrationBean
同模塊里面有相關默認Filter
web->servlet->filter

3、自定義Filter
1）使用Servlet3.0的注解進行配置
2）啟動類里面增加 @ServletComponentScan，進行掃描

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3）新建一個Filter類，implements Filter，并實現對應的接口
4) @WebFilter 標記一個類為filter，被spring進行掃描
urlPatterns：攔截規則，支持正則

6）控制chain.doFilter的方法的調用，來實現是否通過放行
不放行，web應用resp.sendRedirect("/index.html");
場景：權限控制、用戶登錄(非前端后端分離場景)等

1、官網地址：https://docs.spring.io/spring-boot/docs/2.1.0.BUILD-SNAPSHOT/reference/htmlsingle/#boot-features-embedded-container-servlets-filters-listeners

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package net.xdclass.demo.Filter;import java.io.IOException;import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.annotation.WebFilter; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;@WebFilter(urlPatterns = "/api/*", filterName = "loginFilter") public class LoginFilter implements Filter{/*** 容器加載的時候調用*/@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("init loginFilter");}/*** 請求被攔截的時候進行調用*/@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("doFilter loginFilter");HttpServletRequest req = (HttpServletRequest) servletRequest;HttpServletResponse resp = (HttpServletResponse) servletResponse;String username = req.getParameter("username");if ("xdclass".equals(username)) {filterChain.doFilter(servletRequest,servletResponse);} else {resp.sendRedirect("/index.html");return;}}/*** 容器被銷毀的時候被調用*/@Overridepublic void destroy() {System.out.println("destroy loginFilter");}} filter

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2、Servlet3.0的注解自定義原生Servlet實戰
講解：使用 Servlet3.0的注解自定義原生Servlet和Listener
1、自定義原生Servlet

@WebServlet(name = "userServlet",urlPatterns = "/test/customs")
public class UserServlet extends HttpServlet{

@Override
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.getWriter().print("custom sevlet");
resp.getWriter().flush();
resp.getWriter().close();
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
}

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3、Servlet3.0的注解自定義原生Listener監聽器實戰
簡介：監聽器介紹和Servlet3.0的注解自定義原生Listener監聽器實戰

1、自定義Listener(常用的監聽器 servletContextListener、httpSessionListener、servletRequestListener)
@WebListener
public class RequestListener implements ServletRequestListener {

@Override
public void requestDestroyed(ServletRequestEvent sre) {
// TODO Auto-generated method stub
System.out.println("======requestDestroyed========");
}

@Override
public void requestInitialized(ServletRequestEvent sre) {
System.out.println("======requestInitialized========");

}

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4、SpringBoot2.X自定義攔截器實戰及新舊配置對比(核心知識)
簡介: 講解攔截器使用，Spingboot2.x新版本配置攔截攔截器和舊版本SpringBoot配置攔截器區別講解
類似filter，但是不等同。
1、@Configuration
繼承WebMvcConfigurationAdapter(SpringBoot2.X之前舊版本)

package net.xdclass.demo.intecpter;import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;//@Configuration public class CustomOldWebMvcConfigurer extends WebMvcConfigurerAdapter {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new LoginIntercepter()).addPathPatterns("/api/");super.addInterceptors(registry);}} oldconfig

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SpringBoot2.X 新版本配置攔截器 implements WebMvcConfigurer

package net.xdclass.demo.intecpter;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 CustomWebMvcConfigurer implements WebMvcConfigurer {@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(new LoginIntercepter()).addPathPatterns("/api2/*/**");registry.addInterceptor(new TwoIntercepter()).addPathPatterns("/api2/*/**");//.excludePathPatterns("/api2/xxx/**"); //攔截全部 /*/*/** WebMvcConfigurer.super.addInterceptors(registry);}} 2.X新版本confi

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2、自定義攔截器 HandlerInterceptor （分2步驟：1.新建intercept實現接口 2配置類實現接口，注解注冊，添加新建的攔截器到url映射）
preHandle：調用Controller某個方法之前
postHandle：Controller之后調用，視圖渲染之前，如果控制器Controller出現了異常，則不會執行此方法
afterCompletion：不管有沒有異常，這個afterCompletion都會被調用，用于資源清理

package com.atguigu.springboot.interceptor;import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView;public class LoginIntercepter implements HandlerInterceptor{/*** 進入controller方法之前*/@Overridepublic boolean preHandle(HttpServletRequest request,HttpServletResponse response, Object handler) throws Exception {System.out.println("LoginIntercepter------->preHandle");// String token = request.getParameter("access_token"); // // response.getWriter().print("fail");return HandlerInterceptor.super.preHandle(request, response, handler);}/*** 調用完controller之后，視圖渲染之前*/@Overridepublic void postHandle(HttpServletRequest request,HttpServletResponse response, Object handler,ModelAndView modelAndView) throws Exception {System.out.println("LoginIntercepter------->postHandle");HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);}/*** 整個完成之后，通常用于資源清理*/@Overridepublic void afterCompletion(HttpServletRequest request,HttpServletResponse response, Object handler, Exception ex)throws Exception {System.out.println("LoginIntercepter------->afterCompletion");HandlerInterceptor.super.afterCompletion(request, response, handler, ex);}} logininterceptor

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3、按照注冊順序進行攔截，先注冊，先被攔截

攔截器不生效常見問題：
1）是否有加@Configuration
2）攔截路徑是否有問題 ** 和 *
3）攔截器最后路徑一定要 “/**”， 如果是目錄的話則是 /*/

Filter
是基于函數回調 doFilter()，而Interceptor則是基于AOP思想
Filter在只在Servlet前后起作用，而Interceptor夠深入到方法前后、異常拋出前后等

依賴于Servlet容器即web應用中，而Interceptor不依賴于Servlet容器所以可以運行在多種環境。

在接口調用的生命周期里，Interceptor可以被多次調用，而Filter只能在容器初始化時調用一次。

Filter和Interceptor的執行順序

過濾前->攔截前->action執行->攔截后->過濾后

轉載于:https://www.cnblogs.com/hellowq/p/10523407.html

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