SpringMvc——拦截器学习

1、拦截器(Interceptor)是一种动态拦截方法调用的机制
作用：
在指定的方法调用前后执行预先设定后的的代码
阻止原始方法的执行
2、拦截器与过滤器区别
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

在SpringMvc中进行拦截器配置，一般写在controller下，拦截器为业务层服务。

package com.itheima.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;

@Component
public class ProjectInterceptor implements HandlerInterceptor {
    //原始程序运行之前
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandler....");
        //false代表终止原始操作
        return true;
    }

    //运行之后
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandler...");
    }
    //运行之后
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}

在springMvc中加载拦截器

package com.itheima.config;

import com.itheima.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.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;

@Configuration
public class SpringWebSupport extends WebMvcConfigurationSupport {
    @Autowired
    private ProjectInterceptor projectInterceptor;

    @Override
    protected void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/pages/**").addResourceLocations("/pages/");
    }

//    拦截器
//设置拦截器对象和拦截请求
    @Override
    protected void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books"); //配置拦截路径
    }
}

加载完之后，需要在SpringMvc配置文件中进行扫描。

拦截器的执行流程