Spring Bean扩展接口 -- ApplicationContextAware源码分析

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一、首先我们看一下ApplicationContextAware接口的源码

package org.springframework.context;import org.springframework.beans.BeansException;import org.springframework.beans.factory.Aware;public interface ApplicationContextAware extends Aware {void setApplicationContext(ApplicationContext applicationContext) throws BeansException;}

package org.springframework.beans.factory;            public abstract interface Aware  {      }

1.ApplicationContext是上下文的意思，我们编写的类实现ApplicationContextAware接口就可以获取Spring容器的应用上下文环境。当容器加载Spring的配置文件时会自动调用ApplicationContextAware的setApplicationContext()方法自动获取ApplicationContext对象，利用ApplicationContext可以得到我们想要的各种上下文，比如最常用的获取Spring实例，接下来会有实例。

2.有人可能会问Aware接口什么都没做为什么还用集成它呢？因为不仅ApplicationContextAware集成了它，其他的接口也同样集成了Aware接口，如：BeanNameAware、BeanFactoryAware和ResourceLoaderAware等。因此集成Aware接口的目的主要是实现java多态的特性。

二、SpringContextHolder实现ApplicationContextAware接口

testwebapp.com.wangzuojia.util;import org.springframework.beans.BeansException;import org.springframework.context.ApplicationContext;import org.springframework.context.ApplicationContextAware;import org.springframework.stereotype.Component;@Componentpublic class SpringContextHolder implements ApplicationContextAware {private static ApplicationContext applicationContext;public static Object getBean(String name) {return applicationContext.getBean(name);}public static <O> O getBean(String name, Class<O> requiredType) {return applicationContext.getBean(name, requiredType);}public static <O> O getBean(Class<O> requiredType) {return applicationContext.getBean(requiredType);}public static <O> String[] getBeanNamesForType(Class<O> requiredType) {return applicationContext.getBeanNamesForType(requiredType);}/** * 实现ApplicationContextAware的setApplicationContext方法，设置上下文环境 */@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.applicationContext = applicationContext;}}

三、实例

public class GenerationApplicationNoUtil {/** * 获取下一个流水号，获取时根据查询条件判断，如果没有则新加一条记录，否则加1 * @throws Exception */public static String getMaxSerialNumber(String branchcode, String year,String orgcode, String serialtype, String hmlb, String productcode, int limitLength, String padStr) {......//此处使用ApplicationContextAware获取Spring BeanTCounterService tCounterService = SpringContextHolder.getBean(TCounterService.class);String simpleCode = tCounterService.getMaxSerialNumber(branchcode, year,orgcode, serialtype, hmlb, productcode);return simpleCode;} catch (Exception e) {logger.error("获取流水号报错：" + ExceptionUtil.getErrorMsg(e), e);throw new BusinessException("获取流水号报错："+ ExceptionUtil.getErrorMsg(e), e);} finally {// 还原为之前正在使用的dbtypeif (oldDbtype != null) {DataSourceContextHolder.setDataSource(oldDbtype);}}}}

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