9. SpringMvc拦截器

news2025/1/11 10:18:43

1. 拦截器概念和作用

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：
1. 在指定的方法调用前后执行预先设定的代码
2. 阻止原始方法的执行
3. 总结：增强
核心原理：AOP思想

2. 拦截器和过滤器的区别

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

3. 拦截器代码实现

3.1 定义一个类，实现HandlerInterceptor接口

package com.zhang.controller.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;
//注意当前类必须受Spring容器控制
@Component//定义拦截器类，实现HandlerInterceptor接口
public class ProjectInterceptor implements HandlerInterceptor {

     //原始方法调用前执行的内容
    //返回值类型可以拦截控制的执行，true放行，false终止
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("Controller执行前面");
        return true;
    }
     //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("Controller执行后面");
    }
     //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("Controller执行完成后");
    }
}

3.2 配置加载拦截器,定义一个类继承 WebMvcConfigurationSupport

这个类注意要被SpringMvcConfig配置类扫描到，不然不生效

package com.zhang.config;

import com.zhang.controller.interceptor.ProjectInterceptor;
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.WebMvcConfigurationSupport;

@Configuration
public class MvcSupportConfig  extends WebMvcConfigurationSupport {

    @Autowired
    private ProjectInterceptor projectInterceptor;
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(projectInterceptor).addPathPatterns("/**");//拦截所有请求
    }
}

3.3 Controller

package com.zhang.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/books")
public class BookController {
    
    @GetMapping()
    public String  save(){
        System.out.println("正在执行Controller："+"Book...Save");

        return "Hello SpringMvc";
    }
}

3.4 posatman发送请求，后台打印结果

4. 拦截器流程分析

5. 拦截器参数

5.1 前置处理

//原始方法调用前执行的内容
//返回值类型可以拦截控制的执行，true放行，false终止
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    System.out.println("preHandle..."+contentType);
    return true;
}

参数
1. request:请求对象
2. response:响应对象
3. handler:被调用的处理器对象，本质上是一个方法对象，对反射技术中的Method对象进行了再包装
返回值
返回值为false，后面的Controller方法不执行

5.2 后置处理

//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...");
}

参数
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，并进行跳转

注意：如果处理器方法出现异常了，该方法不会执行

5.3 完成后处理

//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...");
}

参数
ex:如果处理器执行过程中出现异常对象，可以针对异常情况进行单独处理

注意：无论处理器方法内部是否出现异常，该方法都会执行。

6. 拦截器链配置

6.1 多个拦截器配置

定义第二个拦截器

@Component
public class ProjectInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...222");
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...222");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...222");
    }
}

配置第二个拦截器

package com.zhang.config;

import com.zhang.controller.interceptor.ProjectInterceptor;
import com.zhang.controller.interceptor.ProjectInterceptor2;
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.WebMvcConfigurationSupport;

@Configuration
public class MvcSupportConfig  extends WebMvcConfigurationSupport {

    @Autowired
    private ProjectInterceptor2 projectInterceptor2;
    @Autowired
    private ProjectInterceptor projectInterceptor;
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(projectInterceptor).addPathPatterns("/**");//拦截所有请求
        registry.addInterceptor(projectInterceptor2).addPathPatterns("/**");
    }
}