1.宣告 某個Bean 僅在一定條件下 才初始化Bean,否則 就不初始化。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.ThreadPoolExecutor;


@Configuration
public class ThreadPoolConfiguration {

    @Value(
 
"${thread.pool.core.size}")
    private Integer coreSize;

    @Value("${thread.pool.max.size}")
    private Integer maxSize;

    @Value("${thread.pool.queue.capacity}")
    private Integer queueCapacity;

    @Value("${thread.pool.alive.seconds}")
    private Integer keepAliveSeconds;

    　//宣告執行緒池1   僅在appCode=swappingA 或者 B的時候，該Bean即該執行緒池才 初始化
    @Bean(name 
 
= "myTaskExecutor")
    @ConditionalOnExpression("'${app.code}'.equals('swappingA')  || '${app.code}'.equals('swappingB')")
    public ThreadPoolTaskExecutor myTaskExecutor() {
        ThreadPoolTaskExecutor myTaskExecutor = new ThreadPoolTaskExecutor();
        myTaskExecutor.setCorePoolSize(coreSize);
        myTaskExecutor.setMaxPoolSize(maxSize);
        myTaskExecutor.setQueueCapacity(queueCapacity);
        myTaskExecutor.setKeepAliveSeconds(keepAliveSeconds);
        myTaskExecutor.setThreadNamePrefix("my-task-pool-");
        return myTaskExecutor;
    }
    
     //宣告執行緒池2  僅在appCode=swappingC 或者 B的時候，該Bean即該執行緒池才 初始化
    @Bean(name = "myTaskExecutor2")
    @ConditionalOnExpression("'${app.code}'.equals('swappingC')  || '${app.code}'.equals('swappingB')")
    public ThreadPoolTaskExecutor myTaskExecutor2() {
        ThreadPoolTaskExecutor myTaskExecutor2 = new ThreadPoolTaskExecutor();
        myTaskExecutor2.setCorePoolSize(coreSize);
        myTaskExecutor2.setMaxPoolSize(maxSize);
        myTaskExecutor2.setQueueCapacity(queueCapacity);
        myTaskExecutor2.setKeepAliveSeconds(keepAliveSeconds);
        myTaskExecutor2.setThreadNamePrefix("my-task2-pool-");
        return myTaskExecutor2;
    }
    
}

2.如上，如果在swappingA應用啟動時，通過@Resource去獲取執行緒池2，就會啟動失敗，找不到該Bean

@Resource
private ThreadPoolTaskExecutor myTaskExecutor2;

或者

@Resource(name = "myTaskExecutor2")
private ThreadPoolTaskExecutor myTaskExecutor2;

啟動就會報錯

Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor' available: expected single matching bean but found 1: myTaskExecutor

或者

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'reportTaskExecutor' available

3.所以，想要在swappingA啟動時候，也能取到myTaskExecutor2 該Bean,修改@ConditionalOnExpression的條件

如下標紅新增

 @Bean(name = "myTaskExecutor2")
    @ConditionalOnExpression(" '${app.code}'.equals('swappingA')  || '${app.code}'.equals('swappingC')  || '${app.code}'.equals('swappingB')")
    public ThreadPoolTaskExecutor myTaskExecutor2() {
        ThreadPoolTaskExecutor myTaskExecutor2 = new ThreadPoolTaskExecutor();
        myTaskExecutor2.setCorePoolSize(coreSize);
        myTaskExecutor2.setMaxPoolSize(maxSize);
        myTaskExecutor2.setQueueCapacity(queueCapacity);
        myTaskExecutor2.setKeepAliveSeconds(keepAliveSeconds);
        myTaskExecutor2.setThreadNamePrefix("my-task2-pool-");
        return myTaskExecutor2;
    }