1. 自定义拦截器

在springboot中，使用自定义拦截器，只需要将类实现HandlerIntercepter接口(与原生的filter也基本差不多)。

HandlerIntercepeter源码：


package org.springframework.web.servlet;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.lang.Nullable;
import org.springframework.web.method.HandlerMethod;

public interface HandlerInterceptor {

	default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		return true;
	}
	
	default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
			@Nullable ModelAndView modelAndView) throws Exception {
	}

	default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler,
			@Nullable Exception ex) throws Exception {
	}

}

preHandle()：当某个 url 已经匹配到对应的 Controller 中的某个方法，且在这个方法执行之前去执行。返回 true 则放行，返回 false 则不会向后执行。

postHandle()：当某个 url 已经匹配到对应的 Controller 中的某个方法，且在执行完了该方法，但是在 DispatcherServlet视图渲染之前。所以在这个方法中有个 ModelAndView 参数，可以在此做一些修改动作。

afterCompletion()：在整个请求处理完成后（包括视图渲染）执行，这时做一些资源的清理工作，这个方法只有在 preHandle(……) 被成功执行后并且返回 true才会被执行。

2. 拦截器登录验证的小demo

只有当用户正确登录以后，才允许用户去访问网站的其他页面和资源，即初始时拦截掉所有请求，除了登录页面的请求，登录成功以后放行访问其他页面。

目录结构如下：

在这里插入图片描述

2.1 配置pom.xml

配置pom.xml

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

2.2 创建User的bean组件

使用lombok，来快速生成有参无参构造器，以及get ,set方法和toString()方法

package com.robin.boot.bean;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

@ToString
@NoArgsConstructor
@AllArgsConstructor
@Data
public class User {
    private String userName;
    private String password;
}

2.3 创建需要的表单页面以及登录成功的页面

index.html:

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>登录页面</title>
</head>
<body>
    <h3 th:text="${msg}">title</h3>
    <form action="/login" method="post">
        <input type="text" name="userName"><br>
        <input type="password" name="password"><br>
        <input type="submit" value="登录">
    </form>
</body>
</html>

show.html:

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>显示页面</title>
</head>
<body>
    <h3 th:text="${msg}">title</h3>
    账号:<p th:text="${loginUser.userName}">账号xxx</p>
    密码:<p th:text="${loginUser.password}">密码xxx</p>
</body>
</html>

2.4 编写controller映射关系

package com.robin.boot.controller;

import com.robin.boot.bean.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;

@Controller
public class LoginController {

    @PostMapping("/login")
    public String login(User user, Model model){
        System.out.println(user);
        if ("robin".equals(user.getUserName())&&"123456".equals(user.getPassword())){
            model.addAttribute("loginUser",user);
            return "show";
        }else{
            model.addAttribute("msg","登录失败,请检查账号密码信息..");
            return "index";
        }
    }
    
}

2.5 自定义拦截器类，实现intercepetor接口

package com.robin.boot.interceptor;

import lombok.extern.slf4j.Slf4j;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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


@Slf4j
public class LoginInterceptor implements HandlerInterceptor {

    // 目标方法执行之前
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 拦截请求输出
        String requestURI = request.getRequestURI();
        log.info("拦截了请求{}",requestURI);

        // 登录检查逻辑，是否登录，登录成功以后放行资源，未登录则拦截资源
        HttpSession session = request.getSession();
        Object loginUser = session.getAttribute("loginUser");

        if (loginUser!=null){
            // 登录成功放行资源
            return true;
        }else{
            // 提示错误信息
            request.setAttribute("msg","请先登录！");
            // 请求转发
            request.getRequestDispatcher("/").forward(request,response);
            // 未登录拦截资源
            return false;
        }


    }

    // 目标方法执行完毕
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
          log.info("postHandle执行{}",modelAndView);
    }

    // 页面渲染以后
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("afterCompletion执行异常{}",ex);
    }
}

2.6注册添加拦截器，自定义springboot配置类

通过addInterceptors(InterceptorRegistry registry)方法，使用registry.addInterceptor()将自定义拦截器注册。

并且通过InterceptorRegistration.addPathPatterns()方法添加拦截的请求，InterceptorRegistration.excludePathPatterns()方法放行请求。

package com.robin.boot.config;

import com.robin.boot.interceptor.LoginInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

// 自定义springboot配置类
@Configuration
public class MyWebConfig implements WebMvcConfigurer {

    // 添加注册拦截器
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor())
                .addPathPatterns("/**") // 拦截所有请求
                .excludePathPatterns("/","/login"); // 放行 / 和 /login请求,
        // 因为例子写的比较简单
        // .excludePathPatterns("/","/login","/css/**","/js/**","/fonts/**","/images/**"); 平常可以写这样
    }
}