Spring Boot 拦截器

**实现自定义拦截器只需要3步： **

1. 创建我们自己的拦截器类并实现 HandlerInterceptor 接口。
2. 创建一个Java类继承WebMvcConfigurerAdapter，并重写 addInterceptors 方法。
3. 实例化我们自定义的拦截器，然后将对像手动添加到拦截器链中（在addInterceptors方法中添加）。

PS：本文重点在如何在Spring-Boot中使用拦截器，关于拦截器的原理请大家查阅资料了解。

LoginInterceptor .java

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
public class LoginInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        System.out.println(">>>>>在请求处理之前进行调用（Controller方法调用之前）");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
       System.out.println(">>>>>>>>>请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println(">>>>>>>>>在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）");
    }
}

LoginInterceptor 2.java

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
public class LoginInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        System.out.println(">>>>>在请求处理之前进行调用（Controller方法调用之前）");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
       System.out.println(">>>>>>>>>请求处理之后进行调用，但是在视图被渲染之前（Controller方法调用之后）");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println(">>>>>>>>>在整个请求结束之后被调用，也就是在DispatcherServlet 渲染了对应的视图之后执行（主要是用于进行资源清理工作）");
    }
}

MyWebAppConfigurer.java

import org.springboot.sample.interceptor.MyInterceptor1;
import org.springboot.sample.interceptor.MyInterceptor2;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
@Configuration
public class MyWebAppConfigurer extends WebMvcConfigurerAdapter { @Override 
  public void addInterceptors(InterceptorRegistry registry) { 
    // 多个拦截器组成一个拦截器链 
    registry.addInterceptor(new LoginInterceptor ()).addPathPatterns("/rest/**"); 
    registry.addInterceptor(new LoginInterceptor2 ()).addPathPatterns("/rest/**");
    super.addInterceptors(registry); 
  }
}