拦截器不能注入bean的问题原因和解决方案

概要

拦截器不能注入bean的问题原因和解决方案

例如：
拦截器经常被用来做登陆验证，日志记录等操作。拦截器是Spring提供的，所以可以将拦截器注成bean，由IOC容器来管理。实现拦截器的方式很简单，主要由以下两个步骤：

步骤1 自定义拦截器MyInterceptor ：

package com.aiit.project.config;

import com.aiit.project.mapper.BlacklistMapper;
import com.aiit.project.model.entity.Blacklist;
import com.aiit.project.service.BlacklistService;
import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.iflytek.uaac.client.rest.context.UaacServiceContext;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.util.List;

/**
 * 拦截器
 */
//@Component
public class MyInterceptor implements HandlerInterceptor {
  

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        .....
        return true;
    }

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

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

步骤 2 配置自定义拦截器：

@Configuration
public class WebConfiguration implements WebMvcConfigurer {

@Override
public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(new MyInterceptor ())
            // 拦截的请求
            .addPathPatterns("/**")
            // 不用拦截的请求
            .excludePathPatterns("/login");
}

}

问题

bean 没有被注入进来
在添加拦截器的时候用的是new MyInterceptor ()，如果想要拦截器生效，必须将拦截器配置到WebMvc的配置类中，就是我们自定义的WebConfiguration类。现在添加拦截器的时候是 new 了一个拦截器，也就是说并没有将拦截器托管给IOC容器，所以就无法引入Spring的bean对象。

如果开启 @Component 同样无法注入bean, 原因是现在添加拦截器的时候是 new 了一个拦截器
所以就无法引入Spring的bean对象。

解决问题思路

将拦截器托管给IOC容器

1.在WebConfiguration注入拦截器

@Component
public class LoginInterceptor implements HandlerInterceptor {
}

@Configuration
public class WebConfiguration implements WebMvcConfigurer {

    @Autowired
    private LoginInterceptor loginInterceptor;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(loginInterceptor);
    }
}

2. 在WebConfiguration将拦截器注成bean

public class LoginInterceptor implements HandlerInterceptor {
}

@Configuration
public class WebConfiguration implements WebMvcConfigurer {

    @Bean
    public LoginInterceptor loginInterceptor(){
        return new LoginInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor( loginInterceptor());
    }
}

3.通过构造器处理

public class LoginInterceptor implements HandlerInterceptor {

    private TokenUtil tokenUtil;

    public LoginInterceptor(TokenUtil tokenUtil) {
        this.tokenUtil = tokenUtil;
    }
}

@Configuration
public class WebConfiguration implements WebMvcConfigurer {

    @Autowired
    private TokenUtil tokenUtil;

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new LoginInterceptor(tokenUtil));
    }
}