Spring实现Bean延迟加载

Spring实现Bean延迟加载

使用spring，则所有bean统一交给spring管理，spring负责初始化、销毁等整个声明周期。所有bean的定义通过配置文件或javaConfig方式。启动时统一初始化并加载至spring的applicationContext中，通过其getBean方法获取。

但有时为了加快系统启动速度，并不需启动时立刻初始化并加载，可以在使用其时才初始化并加载，可以使用@Lazy实现懒加载

有些时候，我们不需要懒加载，但是又希望一些Bean在项目启动后延迟几分钟再初始化加载，具体实现案例如下：

import java.util.List;

import org.apache.commons.collections.CollectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;

/**
 * Description：Bean延迟懒加载实现
 * @author xxx
 * @version 1.0.0
 * @date 2022/2/16
 */
public class SpringContextUtils implements ApplicationContextAware {
	
	public static ApplicationContext applicationContext;
	
	private List<String> lazyLoadBeans;

	private static final Logger logger = LoggerFactory.getLogger(SpringContextUtils.class);

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		SpringContextUtils.applicationContext = applicationContext;
		LazyLoadThread t1 = new LazyLoadThread(applicationContext, lazyLoadBeans);
		t1.start();
	}
    
    public void setLazyLoadBeans(List<String> lazyLoadBeans) {
		this.lazyLoadBeans = lazyLoadBeans;
	}

	class LazyLoadThread extends Thread {
		private ApplicationContext applicationContext;
		private List<String> lazyLoadBeans;
		public LazyLoadThread(ApplicationContext applicationContext, List<String> lazyLoadBeans) {
			this.applicationContext = applicationContext;
			this.lazyLoadBeans = lazyLoadBeans;
		}
		@Override
		public void run() {
			if(CollectionUtils.isEmpty(lazyLoadBeans)) {
				return;
			}
			// 延时3分钟加载
			try {
				Thread.sleep(3 * 60 * 1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			for(String bean : lazyLoadBeans) {
				logger.info("SpringContextUtils lazy Load Bean ： {}", bean);
				applicationContext.getBean(bean);
			}
		}
	}
}

xml方式把Bean添加到Spring容器

    <!-- 延时加载，把需要延时加载的Bean放到list中 -->
	<bean class="com.utils.SpringContextUtils">
		<property name="lazyLoadBeans">
			<list>
				<value>orderDeliveryConfirmConsumer</value>
				<value>updateWeightConsumer</value>
				<value>orderDeliveryForAliyunDeliveryConsumer</value>
				<value>cartonRecommendConsumer</value>
			</list>
		</property>
	</bean>

    <!-- 注意延时加载的Bean,设置懒加载lazy-init="true" -->
    <bean id="orderDeliveryForAliyunDeliveryConsumer" class="com.OrderDeliveryForAliyunDeliveryConsumer" lazy-init="true">
		<constructor-arg name="topic">
			<value>1</value>
		</constructor-arg>
	</bean>