一.需求背景

为了是业务代码和功能的解耦，或者说减少代码的侵入性，像日志和登录拦截，往往都是在每个微服务中都编写相同的代码，为了使开发迅速和减少代码的编写往往都可以抽成一个starter，需要使用此功能的微服务依赖此jar包即可，无需编写相同的代码

此案列拦截非白名单用户的demo

二.demo 代码

新建springboot项目。作为一个插件被其他服务依赖，其实功能就是一个切面的功能方法抽取

starter

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface UserWhiteList {

    String key() default "";

    String result() default "";
}

@Configuration
@ConditionalOnClass(UserWhiteListProperties.class)
@EnableConfigurationProperties(UserWhiteListProperties.class)
// 注意在此类扫描此jar包需要使用的类，就不要再其他依赖此jar包的微服务扫描，只需关注UserWhiteListAutoConfig 就行
@ComponentScan(basePackages = {"com.example.*"})
public class UserWhiteListAutoConfig {

    @Bean("userWhiteListConfig")
    @ConditionalOnMissingBean
    public String userWhiteListConfig(UserWhiteListProperties properties) {
        return properties.getUsers();
    }
}

@ConfigurationProperties("userwhitelist")
public class UserWhiteListProperties {

    private String users;

    public String getUsers() {
        return users;
    }

    public void setUsers(String users) {
        this.users = users;
    }
}

package com.example.whitelist;

import com.alibaba.fastjson.JSON;
import com.example.whitelist.annotation.UserWhiteList;
import org.apache.commons.beanutils.BeanUtils;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.Signature;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.lang.reflect.Method;

/**
 * @author Iron Man
 * @Date 2021-04-21 10:36
 */
@Aspect
@Component
public class UserWhitelistAop {

    private Logger log = LoggerFactory.getLogger(UserWhitelistAop.class);

    @Resource
    private String userWhiteListConfig;

    @Pointcut("@annotation(com.example.whitelist.annotation.UserWhiteList)")
    public void aopPoint() {
    }

    @Around("aopPoint()")
    public Object doRouter(ProceedingJoinPoint jp) throws Throwable {
        Signature signature = jp.getSignature();
        MethodSignature methodSignature = (MethodSignature) signature;
        Method method = jp.getTarget().getClass().getMethod(methodSignature.getName(), methodSignature.getParameterTypes());
        UserWhiteList whiteList = method.getAnnotation(UserWhiteList.class);

        String keyValue = getFiledValue(whiteList.key(), jp.getArgs());
        log.info("userWhitelist handler method：{} value：{}", method.getName(), keyValue);
        if (null == keyValue || "".equals(keyValue)) {
            throw new Exception("未知用户");
        }

        String[] split = userWhiteListConfig.split(",");

        for (String str : split) {
            if (keyValue.equals(str)) {
                return jp.proceed();
            }
        }

        return returnObject(whiteList, method);
    }

    private Object returnObject(UserWhiteList whiteList, Method method) throws IllegalAccessException, InstantiationException {
        Class<?> returnType = method.getReturnType();
        String result = whiteList.result();
        if ("".equals(result)) {
            return returnType.newInstance();
        }
        return JSON.parseObject(result, returnType);
    }

    private String getFiledValue(String filed, Object[] args) {
        String filedValue = null;
        for (Object arg : args) {
            try {
                if (null == filedValue || "".equals(filedValue)) {
                    filedValue = BeanUtils.getProperty(arg, filed);
                } else {
                    break;
                }
            } catch (Exception e) {
                if (args.length == 1) {
                    return args[0].toString();
                }
            }
        }
        return filedValue;
    }

}

resourdes 下META-INF spring.actories 下的类，服务启动时默认会引入此类，也可以在微服务中使用@Import注解来替代

org.springframework.boot.autoconfigure.EnableAutoConfiguration=com.example.whitelist.config.UserWhiteListAutoConfig

三.测试

1.新建一个测试的微服务 使用@UserWhiteList 注解切面来拦截请求

@RestController
public class UserController {

    @UserWhiteList(key = "userId", result = "{\"code\":\"1111\",\"info\":\"非白名单用户被拦截！\"}")
    @GetMapping(path = "/api/queryUserInfo")
    public UserVo queryUserInfo(@RequestParam String userId) {
        return new UserVo(userId, 20, "徐家汇美罗城五楼");
    }
}

http://localhost:8081/api/queryUserInfo?userId=2222222222222

测试

四.其他

1.starter 需要被打成jar包 即 <packaging>jar</packaging>
2.starter 中需要被使用的类需要被Spring托管，即ComponentScan 可以扫描到
3.spring.actories 中EnableAutoConfiguration 和 @Import 具有相同的效果，都会被当前启动类加载