SpringBoot.12.SpringBoot中的拦截器

- 前言
- 拦截器
- - 介绍
  - 具体实现
  - - 1.新建项目
    - 2.MyInterceptor01.java
    - 3.配置拦截器
    - 4.InterceptorController.java
    - 5.测试
  - 多个拦截器的执行顺序
  - - 1.MyInterceptor01.java
    - 2.MyInterceptor02.java
    - 3.MyWebMvcConfigurer.java
    - 4.测试

前言

拦截器（Interceptor）主要是针对特定处理器进行拦截的。也就是说它拦截的对象是我们的Controller请求。我们可以将Controller中的通用代码进行抽取放在拦截器中，就这一点来讲功能跟我们之前讲的AOP类似（Interceptor底层就是利用AOP来实现的）。在实际开发中Interceptor通常用来做权限校验（现在都有成熟的权限校验框架。比如轻量级的Shiro，还有Spring推出的Spring Security ）

拦截器介绍

拦截器（Interceptor）实现对每一个请求处理前后进行相关的业务处理，类似与servlet中的Filter。
SpringMVC 中的 Interceptor 拦截请求是通过 HandlerInterceptor 接口来实现的。

拦截器可以通过以下几种方式进行实现：

实现 SpringMVC 的 HandlerInterceptor 接口；
继承实现了 HandlerInterceptor 接口的类，比如 SpringMVC 已经提供的实现了HandlerInterceptor 接口的抽象类 HandlerInterceptorAdapter；
实现 SpringMVC 的 WebRequestInterceptor 接口；
继承实现了 WebRequestInterceptor 的类；

具体实现 1.新建项目

在上一节SpringBoot.11.IDEA中如何快速复制当前父项目中的一个Module为新的项目中我们已经准备好了Module – springboot-08-interceptor。如下图所示：

2.MyInterceptor01.java

package com.christy.config.interceptors;

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;


public class MyInterceptor01 implements HandlerInterceptor {

    private static final Logger log = LoggerFactory.getLogger(MyInterceptor01.class);

    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("==========MyInterceptor01==========handler=========" + handler);
        log.info("==========MyInterceptor01==========preHandle=========");
        return true;
    }

    
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("==========MyInterceptor01==========postHandle=========");
    }

    
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("==========MyInterceptor01==========ex========={}", ex);
        log.info("==========MyInterceptor01==========afterCompletion=========");
    }
}

3.配置拦截器

我们进入到MyWebMvcConfigurer.java中，按快捷键Alt+Insert，选择Implement Methods…或者直接按快捷键Alt+Shift+P。如下图所示：

在Select Methods to Implement中选择addIntefceptors()这个方法。如下图所示：

修改MyWebMvcConfigurer.java内容如下所示：

import com.christy.config.interceptors.MyInterceptor01;
import com.christy.constants.FileConstants;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;


@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {

    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor01())
                .addPathPatterns("/interceptor
        String os = System.getProperty("os.name");
        if(os.toLowerCase().startsWith("win")){
            // Windows虚拟路径映射本地磁盘
            registry.addResourceHandler(FileConstants.fileVirtualPath + "**").addResourceLocations("file:" + FileConstants.fileWindowsPath);
        } else {
            // Linux虚拟路径映射本地磁盘
            registry.addResourceHandler(FileConstants.fileVirtualPath + "**").addResourceLocations("file:" + FileConstants.fileLinuxPath);
        }
    }
}

4.InterceptorController.java

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;


@RestController
@RequestMapping("/interceptor")
public class InterceptorController {

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

    @RequestMapping("sayHello")
    public String sayHello(){
        log.info("Hello Interceptor…");
        return "interceptor";
    }
}

5.测试

启动项目，浏览器访问http://localhost:8808/interceptor/sayHello，注意观察页面和控制台输出：

我们改造一下sayHello()方法抛出一个异常，如下所示：

@RequestMapping("sayHello")
public String sayHello(){
  log.info("Hello Interceptor…");
  int i = 1/0;
  return "interceptor";
}

重新启动项目，浏览器访问http://localhost:8808/interceptor/sayHello，注意观察页面和控制台输出：

多个拦截器的执行顺序 1.MyInterceptor01.java

我们修改一下MyInterceptor01.java如下：

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;


public class MyInterceptor01 implements HandlerInterceptor {

    private static final Logger log = LoggerFactory.getLogger(MyInterceptor01.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("==========MyInterceptor01==========1=========");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("==========MyInterceptor01==========2=========");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("==========MyInterceptor01==========3=========");
    }
}

2.MyInterceptor02.java

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;


public class MyInterceptor02 implements HandlerInterceptor {

    private static final Logger log = LoggerFactory.getLogger(MyInterceptor02.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("==========MyInterceptor02==========4=========");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        log.info("==========MyInterceptor02==========5=========");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        log.info("==========MyInterceptor02==========6=========");
    }
}

3.MyWebMvcConfigurer.java

import com.christy.config.interceptors.MyInterceptor01;
import com.christy.config.interceptors.MyInterceptor02;
import com.christy.constants.FileConstants;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;


@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {

    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor01())
                .addPathPatterns("/interceptor
        String os = System.getProperty("os.name");
        if(os.toLowerCase().startsWith("win")){
            // Windows虚拟路径映射本地磁盘
            registry.addResourceHandler(FileConstants.fileVirtualPath + "**").addResourceLocations("file:" + FileConstants.fileWindowsPath);
        } else {
            // Linux虚拟路径映射本地磁盘
            registry.addResourceHandler(FileConstants.fileVirtualPath + "**").addResourceLocations("file:" + FileConstants.fileLinuxPath);
        }
    }
}

4.测试

重新启动项目，浏览器访问http://localhost:8808/interceptor/sayHello，注意观察控制台输出：

多个拦截器注册以后按照注册的顺序以栈式结构存储，上面我们配置了两个拦截器，MyInterceptor01先入栈，MyInterceptor02后入栈；所以当请求来了之后：

首先，进入MyInterceptor01的preHandle打印输出1，再进入MyInterceptor02的preHandle打印输出4；这是一个入栈的过程

其次访问方法主体打印输出方法体内的logger

然后，进入MyInterceptor02的postHandle打印输出5，再进入MyInterceptor01的postHandle打印输出2；这是一个出栈的过程

最后，进入MyInterceptor02的afterCompletion打印输出6，再进入MyInterceptor01的afterCompletion打印输出3；这也是一个出栈的过程

按照上面的描述如果我们更换两个拦截器的顺序，让MyInterceptor02先入栈，MyInterceptor01后入栈；那么打印的结果应该是4->1->2->5->3->6。

我们修改MyWebMvcConfigurer.java的代码更换两个拦截器的顺序如下：

import com.christy.config.interceptors.MyInterceptor01;
import com.christy.config.interceptors.MyInterceptor02;
import com.christy.constants.FileConstants;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;


@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {

    
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor01())
                .addPathPatterns("/interceptor
        String os = System.getProperty("os.name");
        if(os.toLowerCase().startsWith("win")){
            // Windows虚拟路径映射本地磁盘
            registry.addResourceHandler(FileConstants.fileVirtualPath + "**").addResourceLocations("file:" + FileConstants.fileWindowsPath);
        } else {
            // Linux虚拟路径映射本地磁盘
            registry.addResourceHandler(FileConstants.fileVirtualPath + "**").addResourceLocations("file:" + FileConstants.fileLinuxPath);
        }
    }
}

然后重启项目，浏览器访问http://localhost:8808/interceptor/sayHello，注意观察控制台输出：

SpringBoot.12.SpringBoot中的拦截器

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