springboot实现拦截器

你首先需要一个搭建好的springboot项目，具体怎么搭建我还没有相应的随笔可以交给你，可以自己上网上看一下，学习一下，之后我要是总结出来的话，这里面我会通知的

首先这个项目的目录结构是这样子的

首先在Controller里面写上你想要展示的内容

package com.example.springBoot;

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

@RestController
public class Controller {
    @RequestMapping(value="/")
    public String Hello(){
        return "hello";
    }
}

然后自定义一个拦截器

package com.example.springBoot;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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

public class InterceptorUtil implements HandlerInterceptor {
    /**
     * todo : 在请求处理之前调用，此处当userId==lx时才能正常进入控制器，否则被拦截
     * @param httpServletRequest
     * @param httpServletResponse
     * @param o
     * @return
     * @throws Exception
     */
    @Override
    public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
        String userId = httpServletRequest.getParameter("userId");//接收一个userId的参数
        if("lx".equals(userId))
            return  true;
        else
            return false;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
        System.out.println("执行postHandle方法");
    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
        System.out.println("执行afterCompletion方法");
    }
}

preHandle：请求之前调用，返回值为boolean类型，然后返回true的时候执行下面的两个方法，返回false则不执行

postHandle：请求之后视图渲染之前调用

afterCompletion：视图渲染之后调用

然后写MyWebAppConfigurer，将上述拦截器注入bean中

package com.example.springBoot;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

/**
 * 注册拦截器
 * @author lixue
 *
 */
@Configuration
public class MyWebAppConfigurer extends WebMvcConfigurerAdapter {
    @Bean   //把拦截器注入为bean
    public HandlerInterceptor getMyInterceptor(){
        return new InterceptorUtil();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(getMyInterceptor()).addPathPatterns("/**");
        super.addInterceptors(registry);
    }
}

然后运行Application

package com.example.springBoot;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

}

右键

然后访问

控制台打印了postHandle    afterCompletion这两个方法的输出语句

接下来换一下

什么都没有，控制台也没有继续打印（这是上面操作userId=lx打印出来的userId=lx1并没有打印）

这样就实现了一个简单的拦截器