springMVC学习--4 拦截器

拦截器用于对请求处理前后进行相关业务处理
示例：

1. 拦截器

package com.interceptor;

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

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class DemoInterceptor extends HandlerInterceptorAdapter {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        long startTime = System.currentTimeMillis();
        request.setAttribute("startTime", startTime);
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        long startTime = (Long) request.getAttribute("startTime");
        long endTime = System.currentTimeMillis();
        request.removeAttribute("startTime");
        System.out.println("This request needs processing time: " + (endTime - startTime) + " ms.");
        request.setAttribute("handingTime", endTime-startTime);
    }
}

2. 配置类中添加拦截器

package com.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.servlet.view.JstlView;

import com.interceptor.DemoInterceptor;

@Configuration
@ComponentScan("com")
@EnableWebMvc
public class MvcConfig extends WebMvcConfigurerAdapter {
    @Bean
    InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver viewResolver = 
                new InternalResourceViewResolver();
        viewResolver.setPrefix("/WEB-INF/classes/views/");
        viewResolver.setSuffix(".jsp");
        //JstlView is used to support java standard tag library and create jsp view
        viewResolver.setViewClass(JstlView.class); 
        return viewResolver;
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/assets/**").addResourceLocations("classpath:/assets/");
    }
    // 拦截器
    @Bean 
    DemoInterceptor demoInterceptor() {
        return new DemoInterceptor();
    }

    // 添加拦截器
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(demoInterceptor());
    }

}