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1. 拦截器概念

(1) 浏览器发送一个请求会先到Tomcat的web服务器

(2) Tomcat服务器接收到请求以后，会去判断请求的是静态资源还是动态资源

(3) 如果是静态资源，会直接到Tomcat的项目部署目录下去直接访问

(4) 如果是动态资源，就需要交给项目的后台代码进行处理

(5) 在找到具体的方法之前，我们可以去配置过滤器(可以配置多个Filter)，按照顺序进行执行

(6) 然后进入到到中央处理器(SpringMVC中的内容)，SpringMVC会根据配置的规则进行拦截

(7) 如果满足规则，则进行处理，找到其对应的controller类中的方法进行执行,完成后返回结果

(8) 如果不满足规则，则不进行处理

拦截器要做的事情：

• 拦截器（Interceptor）是一种动态拦截方法调用的机制，在SpringMVC中动态拦截控制器方法的执行
• 作用:
  • 在指定的方法调用前后执行预先设定的代码
  • 阻止原始方法的执行
  • 拦截器就是用来做增强

注意区分过滤器和拦截器：

• 归属不同：Filter属于Servlet技术，Interceptor属于SpringMVC技术
• 拦截内容不同：Filter对所有访问进行增强，Interceptor仅针对SpringMVC的访问进行增强

2. 拦截器入门案例

2.1 环境准备

步骤1：创建一个Web的Maven项目
步骤2：在pom.xml中添加所需的jar包

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.example</groupId><artifactId>springMVC_12_interceptor</artifactId><version>1.0-SNAPSHOT</version><packaging>war</packaging><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target></properties><dependencies><dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version><scope>provided</scope></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.2.10.RELEASE</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.9.0</version></dependency></dependencies><build><plugins><plugin><groupId>org.apache.tomcat.maven</groupId><artifactId>tomcat7-maven-plugin</artifactId><version>2.1</version><configuration><port>8080</port><path>/</path></configuration></plugin></plugins></build>
</project>

步骤3：编写Controller

package com.itheima.controller;import com.itheima.domain.Book;
import org.springframework.web.bind.annotation.*;/*** @Author Mr.Lu* @Date 2023/2/11 15:16* @ClassName BookController* @Version 1.0*/
@RestController
@RequestMapping("/books")
public class BookController {@PostMappingpublic String save(@RequestBody Book book){System.out.println("book save ..." + book);return "{'module':'book save'}";}@DeleteMapping("/{id}")public String delete(@PathVariable Integer id){System.out.println("book delete..." + id);return "{'module':'book delete'}";}@PutMappingpublic String update(@RequestBody Book book){System.out.println("book update ... " + book);return "{'module':'book update'}";}@GetMapping("/{id}")public String getById(@PathVariable Integer id){System.out.println("book getById ... " + id);return "{'module':'book getById'}";}@GetMappingpublic String getAll(){System.out.println("book getAll...");return "{'module':'book getAll'}";}
}

步骤4：创建模型类Book

package com.itheima.domain;/*** @Author Mr.Lu* @Date 2023/2/11 15:12* @ClassName Book* @Version 1.0*/
public class Book {private String name;private double price;public Book() {}public Book(String name, double proce) {this.name = name;this.price = proce;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getProce() {return price;}public void setProce(double proce) {this.price = proce;}@Overridepublic String toString() {return "Book{" +"name='" + name + '\'' +", proce=" + price +'}';}
}

步骤5：创建对应的配置类

@Configuration
@ComponentScan({"com.itheima.controller"})
@EnableWebMvc
public class SpringMvcConfig {
}

package com.itheima.config;import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;import javax.servlet.Filter;public class ServletContainersInitConfig extends AbstractDispatcherServletInitializer {/*** 加载springmvc配置类** @return*/@Overrideprotected WebApplicationContext createServletApplicationContext() {AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();ctx.register(SpringMvcConfig.class);return ctx;}/*** 设置由springmvc控制器处理的请求映射路径** @return*/@Overrideprotected String[] getServletMappings() {return new String[]{"/"};}/*** 加载spring配置类** @return*/@Overrideprotected WebApplicationContext createRootApplicationContext() {
//        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();
//        ctx.register(SpringConfig.class);
//        return ctx;return null;}// 乱码处理@Overrideprotected Filter[] getServletFilters() {CharacterEncodingFilter filter = new CharacterEncodingFilter();filter.setEncoding("UTF-8");return new Filter[]{filter};}
}

2.2 拦截器开发

步骤1: 创建拦截器类

在com.itheima目录下面建一个interceptor包，在interceptor包下面建一个实现HandlerIntercepror接口的类，并重写里面的额三个方法。

注意： 拦截器中的preHandler方法，如果返回true,则代表放行，会执行原始Controller类中要请求的方法，如果返回false，则代表拦截，后面的就不会再执行了。

当有拦截器后，请求会先进入preHandle方法，

1. 如果方法返回true，则放行继续执行后面的handle[controller的方法]和后面的方法

2. 如果返回false，则直接跳过后面方法的执行。

package com.itheima.interceptor;import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;// 定义拦截器类，实现HandlerInterceptor接口
// 注意当前类必须受Spring容器控制
@Component
public class ProjectInterceptor implements HandlerInterceptor {@Override// 原始方法调用前执行的内容public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("preHandle...");return true;}@Override// 原始方法调用后执行的内容public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("postHandle...");}@Override// 原始方法调用完成后执行的内容public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {System.out.println("afterCompletion...");}
}

步骤2: 配置拦截器类

在config目录下创建一个类来配置拦截器类

package com.itheima.config;import com.itheima.interceptor.*;
import org.springframework.beans.factory.annotation.Autowired;
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.WebMvcConfigurationSupport;/*** @Author Mr.Lu* @Date 2023/2/12 15:13* @ClassName SpringMvcSupport* @Version 1.0*/
@Configuration
public class SpringMvcSupport extends WebMvcConfigurationSupport {@Autowired(required = false)private ProjectInterceptor projectInterceptor;//    @Override
//    protected void addResourceHandlers(ResourceHandlerRegistry registry) {
//        registry.addResourceHandler("/pages/**").addResourceLocations("/pages/");
//    }@Overrideprotected void addInterceptors(InterceptorRegistry registry) {// 配置拦截器registry.addInterceptor(projectInterceptor).addPathPatterns("/books", "/books/*"); // 为可变参数，可以写几种路径}
}

步骤3: SpringMVC添加SpringMvcSupport包扫描和interceptor包扫描

@Configuration
@ComponentScan({"com.itheima.controller", "com.itheima.interceptor", "com.itheima.config"})
@EnableWebMvc
public class SpringMvcConfig {
}

步骤4: 简化SpringMvcSupport的编写

让SpringMvcConfig类实现WebMvcConfigurer接口。

@Configuration
@ComponentScan({"com.itheima.controller"})
@EnableWebMvc
// 实现WebMvcConfigurer接口可以简化开发，但具有一定的侵入性
public class SpringMvcConfig implements WebMvcConfigurer {@Autowiredprivate ProjectInterceptor projectInterceptor;@Overridepublic void addInterceptors(InterceptorRegistry registry) {//配置多拦截器registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");}
}

5 测试

访问http://localhost:8080/books

访问http://localhost:8080/books/666

3. 拦截器参数解析（了解）

3.1 前置处理方法

原始方法之前运行preHandle

public boolean preHandle(HttpServletRequest request,HttpServletResponse response,Object handler) throws Exception {System.out.println("preHandle");return true;
}

• request:请求对象
• response:响应对象
• handler:被调用的处理器对象，本质上是一个方法对象，对反射中的Method对象进行了再包装

3.2 后置处理方法

原始方法运行后运行，如果原始方法被拦截（前置方法返回false），则不执行

public void postHandle(HttpServletRequest request,HttpServletResponse response,Object handler,ModelAndView modelAndView) throws Exception {System.out.println("postHandle");
}

modelAndView:如果处理器执行完成具有返回结果，可以读取到对应数据与页面信息，并进行调整

3.3 完成处理方法

拦截器最后执行的方法，无论原始方法是否执行（只要前置方法返回true,那么完成处理方法就一定执行）

public void afterCompletion(HttpServletRequest request,HttpServletResponse response,Object handler,Exception ex) throws Exception {System.out.println("afterCompletion");
}

4. 拦截器链配置

步骤1:创建拦截器类：实现接口，并重写接口中的方法

拦截器2： ProjectInterceptor2

package com.itheima.interceptor;import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** @Author Mr.Lu* @Date 2023/2/12 15:09* @ClassName ProjectInterceptor* @Version 1.0*/// 定义拦截器类，实现HandlerInterceptor接口
// 注意当前类必须受Spring容器控制
@Component
public class ProjectInterceptor2 implements HandlerInterceptor {@Override// 原始方法调用前执行的内容public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("preHandle...222");return true;}@Override// 原始方法调用后执行的内容public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("postHandle...222");}@Override// 原始方法调用完成后执行的内容public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {System.out.println("afterCompletion...222");}
}

拦截器3：ProjectInterceptor3

package com.itheima.interceptor;import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** @Author Mr.Lu* @Date 2023/2/12 15:09* @ClassName ProjectInterceptor* @Version 1.0*/// 定义拦截器类，实现HandlerInterceptor接口
// 注意当前类必须受Spring容器控制
@Component
public class ProjectInterceptor3 implements HandlerInterceptor {@Override// 原始方法调用前执行的内容public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {System.out.println("preHandle...333");return true;}@Override// 原始方法调用后执行的内容public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("postHandle...333");}@Override// 原始方法调用完成后执行的内容public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {System.out.println("afterCompletion...333");}
}

步骤2:配置拦截器类

package com.itheima.config;import com.itheima.interceptor.*;
import org.springframework.beans.factory.annotation.Autowired;
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.WebMvcConfigurationSupport;/*** @Author Mr.Lu* @Date 2023/2/12 15:13* @ClassName SpringMvcSupport* @Version 1.0*/
@Configuration
public class SpringMvcSupport extends WebMvcConfigurationSupport {@Autowired(required = false)private ProjectInterceptor projectInterceptor;@Autowired(required = false)private ProjectInterceptor2 projectInterceptor2;@Autowired(required = false)private ProjectInterceptor3 projectInterceptor3;//    @Override
//    protected void addResourceHandlers(ResourceHandlerRegistry registry) {
//        registry.addResourceHandler("/pages/**").addResourceLocations("/pages/");
//    }@Overrideprotected void addInterceptors(InterceptorRegistry registry) {// 配置拦截器registry.addInterceptor(projectInterceptor).addPathPatterns("/books", "/books/*");registry.addInterceptor(projectInterceptor2).addPathPatterns("/books", "/books/*");registry.addInterceptor(projectInterceptor3).addPathPatterns("/books", "/books/*");}
}

步骤3:运行程序，观察顺序

拦截器执行的顺序是和配置顺序有关，先进后出。

• 当配置多个拦截器时，形成拦截器链
• 拦截器链的运行顺序参照拦截器添加顺序为准
• 当拦截器中出现对原始处理器的拦截，后面的拦截器均终止运行
• 当拦截器运行中断，仅运行配置在前面的拦截器的afterCompletion操作

注：

1. 当ProjectInterceptor，ProjectInterceptor2，ProjectInterceptor3中的preHandle方法都返回true时，拦截器链执行顺序为：pre1, pre2, pre3, Controller, post3, post2, post1, after3, after2, after1.

2. 当ProjectInterceptor，ProjectInterceptor2中的preHandle方法返回true，ProjectInterceptor3中的preHandle方法返回false时，拦截器链执行顺序为：pre1, pre2, pre3, after2, after1.

3. 当ProjectInterceptor中的preHandle方法返回true，ProjectInterceptor2中的preHandle方法返回false时，拦截器链执行顺序为：pre1, pre2, after1.

4. 当ProjectInterceptor中的preHandle方法返回false时，拦截器链执行顺序为：pre1