@SpringContext通过实现ApplicationContextAware接口动态获取bean

场景：

在代码中需要动态获取spring管理的bean

目前遇到的主要有两种场景：
1.在工具类中需要调用某一个Service完成某一个功能，如DictUtils
2.在实现了Runnable接口的任务类中需要调用某一个Service完成run方法中的功能！

代码：

SpringContextUtils.java

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

@Component
public class ApplicationContextUtils implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        ApplicationContextUtils.applicationContext = applicationContext;
        System.out.println("spring容器在项目构建的时候就执行了");
        String[] beanDefinitionNames = applicationContext.getBeanDefinitionNames();
        for (String beanDefinitionName : beanDefinitionNames) {
            //beanDefinitionName是容器中bean实例的id
            //<bean id="">对应此处的id
            System.out.println(beanDefinitionName);
        }
    }

    /**
     * 当通过接口多个实现时，需要用 beanName区分
     *
     * @param name 注册的 bean名称
     * @param clazz 注册的 bean类型
     * @param <T>
     * @return
     */
    public static <T> T getBean(String name, Class<T> clazz) {
        if (applicationContext == null){
            return null;
        }
        return applicationContext.getBean(name, clazz);
    }

    /***
     * 根据一个bean的类型获取配置文件中相应的bean
     */
    public static <T> T getBeanByClass(Class<T> requiredType) {
        if (applicationContext == null) {
            return null;
        }
        return applicationContext.getBean(requiredType);
    }

    public static ApplicationContext getApplicationContext() {
        return ApplicationContextUtils.applicationContext;
    }
}

控制台输出

spring容器在项目构建的时候就执行了

sqlSessionFactory
org.mybatis.spring.mapper.MapperScannerConfigurer#0
dataSource
org.springframework.beans.factory.config.PropertyPlaceholderConfigurer#0
transactionManager
org.springframework.aop.config.internalAutoProxyCreator
org.springframework.transaction.annotation.AnnotationTransactionAttributeSource#0
org.springframework.transaction.interceptor.TransactionInterceptor#0
org.springframework.transaction.config.internalTransactionAdvisor
myTbItemServiceImpl
org.springframework.context.annotation.internalConfigurationAnnotationProcessor
org.springframework.context.annotation.internalAutowiredAnnotationProcessor
org.springframework.context.annotation.internalRequiredAnnotationProcessor
org.springframework.context.annotation.internalCommonAnnotationProcessor
springContext
org.springframework.context.annotation.ConfigurationClassPostProcessor.importAwareProcessor
org.springframework.context.annotation.ConfigurationClassPostProcessor.enhancedConfigurationProcessor
tbItemMapper

@Service("myTbItemServiceImpl")
public class TbItemServiceImpl implements ITbItemService

这几个注解所在的包是

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.2.5.RELEASE</version>
</dependency>

SpringContextUtils必须放在Spring容器中

要么在xml配置文件中声明，要么加上注解