HandlerInterceptor拦截器

一、什么是拦截器：

二、定义实现类

定义一个Interceptor 非常简单方式有：
1、类要实现Spring 的HandlerInterceptor 接口
2、类继承实现了HandlerInterceptor 接口的类，例如 已经提供的实现了HandlerInterceptor 接口的抽象类HandlerInterceptorAdapter

三、HandlerInterceptor方法

boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
		throws Exception;

void postHandle(
		HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
		throws Exception;

void afterCompletion(
		HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
		throws Exception;

• preHandle：在业务处理器处理请求之前被调用。预处理，可以进行编码、安全控制、权限校验等处理；
• postHandle：在业务处理器处理请求执行完成后，生成视图之前执行。后处理（调用了Service并返回ModelAndView，但未进行页面渲染），有机会修改ModelAndView （这个博主就基本不怎么用了）；
• afterCompletion：在DispatcherServlet完全处理完请求后被调用，可用于清理资源等。返回处理（已经渲染了页面）；

四、拦截器实现

新建TestFilter

package com.xxx.core.filter;

import com.xxx.common.exception.FastRuntimeException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

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


public class TestFilter extends HandlerInterceptorAdapter {
	private final Logger logger = LoggerFactory.getLogger(TestFilter.class);
	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {
		logger.info("request请求地址path[{}] uri[{}]", request.getServletPath(),request.getRequestURI());
		//request.getHeader(String) 从请求头中获取数据
		//从请求头中获取用户token（登陆凭证根据业务而定）
		Long userId= getUserId(request.getHeader("H-User-Token"));
		if (userId != null && checkAuth(userId,request.getRequestURI())){
			return true;
		}
		//这里的异常是我自定义的异常，系统抛出异常后框架捕获异常然后转为统一的格式返回给前端， 其实这里也可以返回false
		throw new FastRuntimeException(20001,"No access");
	}

	/**
	 * 根据token获取用户ID
	 * @param userToken
	 * @return
	 */
	private Long getUserId(String userToken){
		Long userId = null;
		return userId;
	}

	/**
	 * 校验用户访问权限
	 * @param userId
	 * @param requestURI
	 * @return
	 */
	private boolean checkAuth(Long userId,String requestURI){
		return true;
	}

	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
						   ModelAndView modelAndView) throws Exception {}

	@Override
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception {}
}

新建WebAppConfigurer 实现WebMvcConfigurer接口

@Configuration
public class WebAppConfigurer implements WebMvcConfigurer {

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 可添加多个
        registry.addInterceptor(new TestFilter()).addPathPatterns("/**");
    }

    ....
}