1. 引入

Spring容器启动耗时过长, 主要原因是有些Bean做了复杂初始化的工作.
找到这些Bean, 再做针对性的优化, 才能把Spring容器启动耗时降下来.
如果开发对应用代码还不太熟悉, 本文提供了一种方式, 快速找出这些启动非常耗时的Bean.

2. 源码

• LaunchTimeBeanPostProcessor.java (Bean启动时间抓取)

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor;
import org.springframework.beans.factory.support.MergedBeanDefinitionPostProcessor;
import org.springframework.beans.factory.support.RootBeanDefinition;
import org.springframework.stereotype.Component;

/**
 *  Bean启动时间抓取
 *
 *  BeanPostProcessor相关方法
 *  1) postProcessBeforeInstantiation: 实例化前
 *  2) postProcessAfterInstantiation: 实例化后
 *  3) postProcessBeforeInitialization: 初始化前
 *  4) postProcessAfterInitialization: 初始化后
 *
 *  注意: 实现MergedBeanDefinitionPostProcessor, 主要是为了调整当前BeanPostProcessor的执行顺序到最后, 具体参考
 *  BeanPostProcessor注册流程
 *      org.springframework.context.support.AbstractApplicationContext#refresh
 *      org.springframework.context.support.AbstractApplicationContext#registerBeanPostProcessors
 *      org.springframework.context.support.PostProcessorRegistrationDelegate#registerBeanPostProcessors
 *
 * @author liuxianqiang
 * @since 2021/11/17
 */
@Component
public class LaunchTimeBeanPostProcessor implements BeanPostProcessor, InstantiationAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor {

    @Autowired
    private LaunchTimeManager launchInfoManager;

    @Override
    public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) throws BeansException {
        launchInfoManager.beanStart(beanName, System.currentTimeMillis());
        return null;
    }

    @Override
    public boolean postProcessAfterInstantiation(Object bean, String beanName) throws BeansException {
        return true;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        launchInfoManager.beanEnd(beanName, System.currentTimeMillis());
        return bean;
    }

    @Override
    public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
        // ignore
    }
}

• LaunchTimeManager.java (Bean启动时间管理器)

import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.stereotype.Component;

import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Bean启动时间管理器
 *
 * @author liuxianqiang
 * @since 2021/11/17
 */
@Component
public class LaunchTimeManager implements ApplicationListener<ContextRefreshedEvent> {

    private Map<String, LaunchTime> launchTimeMap = new ConcurrentHashMap<>();

    public void beanStart(String beanName, Long startTime) {
        if (Objects.nonNull(launchTimeMap.get(beanName))) {
            System.out.printf("------------%s Bean重复启动 ???-------------\n", beanName);
            return;
        }
        LaunchTime launchTime = new LaunchTime();
        launchTime.setBeanName(beanName);
        launchTime.setStartTime(startTime);
        launchTimeMap.putIfAbsent(beanName, launchTime);
    }

    public void beanEnd(String beanName, Long endTime) {
        if (Objects.isNull(launchTimeMap.get(beanName))) {
            System.out.printf("------------%s Bean还未启动 ???-------------\n", beanName);
            return;
        }
        launchTimeMap.computeIfPresent(beanName, (k, v) -> {
            v.setEndTime(endTime);
            return v;
        });
    }

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        System.out.println("Spring容器启动完成");

        launchTimeMap.values().stream()
                .sorted((e1, e2) -> Long.valueOf(e2.getCostTime() - e1.getCostTime()).intValue())
                .limit(10)
                .forEach(e -> {
                    System.out.printf("启动耗时, beanName:%s, cost:%s \n", e.getBeanName(), e.getCostTime());
                });
    }

    /**
     * Bean启动时间
     */
    public static class LaunchTime {
        private String beanName;

        private Long startTime;

        private Long endTime;

        public String getBeanName() {
            return beanName;
        }

        public void setBeanName(String beanName) {
            this.beanName = beanName;
        }

        public Long getStartTime() {
            return startTime;
        }

        public void setStartTime(Long startTime) {
            this.startTime = startTime;
        }

        public Long getEndTime() {
            return endTime;
        }

        public void setEndTime(Long endTime) {
            this.endTime = endTime;
        }

        public Long getCostTime() {
            return endTime - startTime;
        }
    }
}

3. 原理

Spring Bean 生命周期

4. 测试

• 控制台打印
  
• 测试代码