# 拦截器

![](/files/-LdqfF07LuhIK01fgGQz)

## 1. 定义拦截器

```java
package com.example.demo.interceptor;

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

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

import lombok.extern.slf4j.Slf4j;


@Slf4j
public class FirstInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        log.info("first intercrptor preHandle ...");
        return HandlerInterceptor.super.preHandle(request, response, handler);
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        log.info("first intercrptor postHandle ...");
        HandlerInterceptor.super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        log.info("first intercrptor afterCompletion ...");
        HandlerInterceptor.super.afterCompletion(request, response, handler, ex);
    }



}
```

## 2. 注册拦截器

```java
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.WebMvcConfigurer;

import com.example.demo.interceptor.FirstInterceptor;

@Configuration
public class InterceptorConfiguration implements WebMvcConfigurer {

    @Bean
    public HandlerInterceptor firstInterceptor() {
        return new FirstInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // 由于拦截器加载是在springContext创建之前完成的，如果直接new AuthInterceptor，那么在拦截器中注入实体就为会null
        registry.addInterceptor(firstInterceptor()).addPathPatterns("/**");
    }
}
```

## 3. 测试

```
2019-05-02 11:17:35.300  INFO 23821 --- [nio-8080-exec-1] c.e.demo.interceptor.FirstInterceptor    : first intercrptor preHandle ...
2019-05-02 11:17:35.313  INFO 23821 --- [nio-8080-exec-1] c.e.demo.interceptor.FirstInterceptor    : first intercrptor postHandle ...
2019-05-02 11:17:35.313  INFO 23821 --- [nio-8080-exec-1] c.e.demo.interceptor.FirstInterceptor    : first intercrptor afterCompletion ...
```

## 4. 多个拦截器顺序

* 处理器前方法采用先注册先执行
* 处理器后方法和完成方法采用先注册后执行的顺序

![](/files/-Ldqd4nMxjSIks_2y19J)

```java
package com.example.demo.config;

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.WebMvcConfigurer;

import com.example.demo.interceptor.FirstInterceptor;
import com.example.demo.interceptor.PrometheusInterceptor;

@Configuration
public class InterceptorConfiguration implements WebMvcConfigurer {

    @Bean
    public HandlerInterceptor firstInterceptor() {
        return new FirstInterceptor();
    }
    @Bean
    public HandlerInterceptor prometheusInterceptor() {
        return new PrometheusInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(firstInterceptor()).addPathPatterns("/**");
        registry.addInterceptor(prometheusInterceptor()).addPathPatterns("/**");
    }
}
```

```
2019-05-02 11:22:48.165  INFO 24828 --- [nio-8080-exec-1] c.e.demo.interceptor.FirstInterceptor    : first intercrptor preHandle ...
2019-05-02 11:22:48.165  INFO 24828 --- [nio-8080-exec-1] c.e.d.interceptor.PrometheusInterceptor  : Prometheus intercrptor preHandle ...
2019-05-02 11:22:48.179  INFO 24828 --- [nio-8080-exec-1] c.e.d.interceptor.PrometheusInterceptor  : Prometheus intercrptor postHandle ...
2019-05-02 11:22:48.179  INFO 24828 --- [nio-8080-exec-1] c.e.demo.interceptor.FirstInterceptor    : first intercrptor postHandle ...
2019-05-02 11:22:48.179  INFO 24828 --- [nio-8080-exec-1] c.e.d.interceptor.PrometheusInterceptor  : Prometheus intercrptor afterCompletion ...
2019-05-02 11:22:48.179  INFO 24828 --- [nio-8080-exec-1] c.e.demo.interceptor.FirstInterceptor    : first intercrptor afterCompletion ...
```


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