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java - Spring boot Async + 多线程在未完成所有任务的情况下关闭

问题描述

Spring boot 在未完成所有任务的情况下关闭。

我想从 MYSQL 数据库中收集数据，然后将这些数据导出为 csv 文件。但是 Spring boot 会在一段时间后关闭。

我尝试按照此处和此处的示例进行操作，但似乎

 CompletableFuture.allOf(tasks.toArray(new CompletableFuture[tasks.size()])).join();

不等到所有任务完成。

注意：我有超过 150 个任务需要将数据导出到 CSV 文件。

代码：

MainApplication.java

@SpringBootApplication
@EnableAsync
public class MainApplication implements CommandLineRunner {

@Autowired
private TaskRunner taskrunner;

public static void main(String[] args) throws Exception{
    SpringApplication application = new SpringApplication(MainApplication.class);
    application.setBannerMode(Banner.Mode.OFF);
    application.run(args);
  }

 public void run(String... args) throws Exception {
    taskrunner.executeTasks();
    exit(0);
   }
}

TaskRunner.java

@Service
public class TaskRunner {

@Autowired
public DataCollector dataCollector;

public void executeTask() throws Exception {

  final List<String> parameters = dataCollector.getParameters();
  List<CompletableFuture> tasks = new ArrayList<CompletableFuture>();

  for (String name : parameters) {
    try{
    tasks.add(CompletableFuture.runAsync(() -> dataCollector.ExportDataToCsv(name)));
    }catch(){
      ex.printStackTrace();
      System.out.println("Export failed for Param: "+name);
    }
  }

  CompletableFuture.allOf(tasks.toArray(new CompletableFuture[tasks.size()])).join();

  System.out.println("All Task Finished");
  }
}

数据收集器.java

public class DataCollector{

@Autowired
public DataRepository dataRepository;

 @Async("ThreadPoolTaskExecutor")
 public CompletableFuture<String> ExportDataToCsv(String tableName){
   // Code To export data to csv
 }
}

数据存储库.java

@Repository
public class DataRepository {

   @Qualifier("jdbcExportService")
   @Autowired
   public JdbcTemplate jdbcTemplate;

   public SqlRowSet getParamData(String param){
    String Statement = "select * FROM " + param;
    return jdbcTemplate.queryForRowSet(Statement);
  }
}

数据库配置.java

 @Configuration
 public class DatabaseConfiguration {

@Bean(name="db")
@ConfigurationProperties(prefix = "spring.db")
public DataSource createExportDataSource(){
    return DataSourceBuilder.create().build();
}

@Bean(name = "jdbcExportService")
@Autowired
public JdbcTemplate createJdbcTemplateExportService(@Qualifier("db") DataSource exportServiceDS){
    return new JdbcTemplate(exportServiceDS);
 }
}

输出： 

2019-06-25 14:39:56.868  INFO 13163 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'ThreadPoolTaskExecutor'
2019-06-25 14:39:56.868  INFO 13163 --- [       Thread-2] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2019-06-25 14:39:56.997  INFO 13163 --- [       Thread-2] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2019-06-25 14:39:57.011 DEBUG 13163 --- [       Thread-2] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Before shutdown stats (total=10, active=5, idle=5, waiting=0)
2019-06-25 14:39:57.371 DEBUG 13163 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@2c373ded: (connection evicted)
2019-06-25 14:39:57.991 DEBUG 13163 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@4856fa0b: (connection evicted)
    2019-06-25 14:39:57.994 DEBUG 13163 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@375c83e: (connection evicted)
2019-06-25 14:39:57.995 DEBUG 13163 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@417d7b5b: (connection evicted)
2019-06-25 14:39:57.996 DEBUG 13163 --- [nnection closer] com.zaxxer.hikari.pool.PoolBase          : HikariPool-1 - Closing connection com.mysql.cj.jdbc.ConnectionImpl@77ebb3e9: (connection evicted)
2019-06-25 14:39:58.094 DEBUG 13163 --- [       Thread-2] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - After shutdown stats (total=0, active=0, idle=0, waiting=0)
2019-06-25 14:39:58.095  INFO 13163 --- [       Thread-2] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
2019-06-25 14:39:58.651  WARN 13163 --- [ export-thread1] com.zaxxer.hikari.pool.ProxyConnection   : HikariPool-1 - Connection com.mysql.cj.jdbc.ConnectionImpl@4c18c2a2 marked as broken because of SQLSTATE(08003), ErrorCode(0)

标签： javaspring-boot

解决方案

我读了一点后的猜测，我绝不是这方面的专家。所以这很可能是错误的。

CompletableFuture#join等到您可以从该 CompletableFuture 中提取结果值。CompletableFuture#get抛出检查异常并且CompletableFuture#join是不可中断的。但是两者都做同样的事情，从可完成的未来中提取价值，并在需要时阻止，直到他们这样做。

我认为您正在寻找什么，因为您想在完成后打印某些内容是使用CompletableFuture#thenAccept将在所有内容完成后执行“某事”的东西。

CompletableFuture<Void> allFutures = CompletableFuture.allOf(tasks.toArray(new CompletableFuture[tasks.size()]));
allFutures.thenAccept(Void -> System.out.println("All Task Finished"));

我的猜测是它设置了所有异步任务，然后将其全部传递，然后退出应用程序。

参考：

java-8-completablefuture-in-action

可完成的未来加入vs-get

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