1、原因一：缺少ApplicationContext工具类

package com.performancetest.common.utils;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

import java.util.Map;

/**
 * Spring Context 工具类
 */
@Component
public class SpringContextUtils implements ApplicationContextAware {
    public static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        SpringContextUtils.applicationContext = applicationContext;
    }

    public static Object getBean(String name) {
        return applicationContext.getBean(name);
    }

    public static <T> T getBean(String name, Class<T> requiredType) {
        return applicationContext.getBean(name, requiredType);
    }

    public static boolean containsBean(String name) {
        return applicationContext.containsBean(name);
    }

    public static boolean isSingleton(String name) {
        return applicationContext.isSingleton(name);
    }

    public static Class<? extends Object> getType(String name) {
        return applicationContext.getType(name);
    }

}

2、原因二：跨模块getBean

场景：假如有个工程有common模块和admin(启动类模块)模块，获取getBean的类在admin中，则不会报空指针，如果在common模块中，在admin模块中调用，则会报空指针异常。

解决：使用@Import导入getBean方法所在的类。

@SpringBootApplication
@Import(SpringContextHolder.class)
public class AdminApplication {

    public static void main(String[] args) {
        SpringApplication.run(OathServiceApplication.class, args);
    }

}

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