SpringBean的静态字段/静态属性（static的field），支持Apollo配置热更新吗？-牛翰网

我们知道，springbean的静态field可以通过显式的setter方法（实例方法）实现注入。

下面LaborFeeCalculator，其中的 basePercentage 是一个静态field。通过显式@Value的setter方法来进行配置参数赋值。

@Component
public class LaborFeeCalculator {

    private static FeeRate basePercentage;

    @Value("${bossKg.order-base-percentage:80}")
    public void setBasePercentage(BigDecimal value) {
        basePercentage = FeeRate.PERCENTAGE.of(value);
    }

	...
}

问题：当apollo里的配置项”bossKg.order-base-percentage“的值发生变更时，static变量basePercentage的值会跟着变化吗？也就是说，静态属性（static field）支持配置热更新吗？

我认为是可以的。因为这与field是否静态无关，而与 @Value修饰的setter方法有关。当配置值变更时，这个setter方法就会触发执行。

好奇的我，想看看apollo的相关日志。所以，亲测一下。

下面是测试代码。由后面的执行日志可以看出来，这3种使用@Value的方式，都可以实现配置热更。

package com.emaxcard.boss.modules.usertaxmonthlytotal;

import com.emax.trans.FeeRate;
import com.emaxcard.boss.ServerApplication;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.math.BigDecimal;

@RunWith(SpringRunner.class)
@SpringBootTest(classes = ServerApplication.class)
@Slf4j
class LaborFeeCalculatorTest {

    private FeeRate basePercentage;

    @Value("${bossKg.order-base-percentage:10}")
    public void setBasePercentage(BigDecimal value) {
        basePercentage = FeeRate.PERCENTAGE.of(value);
        log.info("LaborFeeCalculatorTest.order-base-percentage:{}", basePercentage);
    }

    private static FeeRate basePercentage2;

    @Value("${bossKg.order-base-percentage:10}")
    public void setBasePercentage2(BigDecimal value) {
        basePercentage2 = FeeRate.PERCENTAGE.of(value);
        log.info("LaborFeeCalculatorTest.order-base-percentage:{}", basePercentage2);
    }

    @Value("${bossKg.order-base-percentage:10}")
    private String orderBasePercentage;

    @Test
    public void testCalculate() throws InterruptedException {
        for (int i = 0; i < 500; i++) {
            System.out.println("loop"+i + ":" + basePercentage + "++++++++++++++++" + basePercentage2 + "++++++++++++++++" + orderBasePercentage);

            Thread.sleep(1000);
        }
    }
    
}

下面是执行test的日志：

loop0:0.77++++++++++++++++0.77++++++++++++++++77
loop1:0.77++++++++++++++++0.77++++++++++++++++77
loop2:0.77++++++++++++++++0.77++++++++++++++++77
loop3:0.77++++++++++++++++0.77++++++++++++++++77
loop4:0.77++++++++++++++++0.77++++++++++++++++77

// 【【【这时，在apollo控制台修改&发布了property的值 77→93】】】
// 项目中的 LaborFeeCalculator.setBasePercentage 感知到变化 
12:53:56.891 [server-provider-unknown] [Apollo-Config-1] INFO  c.c.f.a.s.property.AutoUpdateConfigChangeListener:? - Auto update apollo changed value successfully, new value: 93, key: bossKg.order-base-percentage, beanName: laborFeeCalculator, method: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculator.setBasePercentage
// 当前test类 LaborFeeCalculatorTest.orderBasePercentage 感知到变化
12:53:56.891 [server-provider-unknown] [Apollo-Config-1] INFO  c.c.f.a.s.property.AutoUpdateConfigChangeListener:? - Auto update apollo changed value successfully, new value: 93, key: bossKg.order-base-percentage, beanName: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculatorTest.ORIGINAL, field: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculatorTest.orderBasePercentage

// 当前test类 LaborFeeCalculatorTest.setBasePercentage 感知到变化
12:53:56.891 [server-provider-unknown] [Apollo-Config-1] INFO  c.c.f.a.s.property.AutoUpdateConfigChangeListener:? - Auto update apollo changed value successfully, new value: 93, key: bossKg.order-base-percentage, beanName: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculatorTest.ORIGINAL, method: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculatorTest.setBasePercentage

// 当前test类 LaborFeeCalculatorTest.setBasePercentage2 感知到变化
12:53:56.891 [server-provider-unknown] [Apollo-Config-1] INFO  c.c.f.a.s.property.AutoUpdateConfigChangeListener:71 - Auto update apollo changed value successfully, new value: 93, key: bossKg.order-base-percentage, beanName: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculatorTest.ORIGINAL, method: com.emaxcard.boss.modules.usertaxmonthlytotal.LaborFeeCalculatorTest.setBasePercentage2

loop5:0.93++++++++++++++++0.93++++++++++++++++93
loop6:0.93++++++++++++++++0.93++++++++++++++++93
...

在日志中可以看到，Apollo分别更新了：