有这么一个需求，数据库20w数据，如果直接从数据库一次性读取比较慢，怎么用多线程 分批次并行读取，然后将List<entity>结果汇总
countdownlatch就能让主线程等待，子线程全部执行完再执行主线程代码！或者jdk8的Future，也能让主线程等待
20w相对来说数据量还是很少的，对查询条件加联合索引试试
@Autowired
private RedisActiveTestsMapper redisActiveTestsMapper;
public List<List<RedisActiveTests>> selectMult(RedisActiveTests redisActiveTests) {
System.out.println("----程序开始运行----");
Date date1 = new Date();
int taskSize = 10;
// 创建一个线程池
ExecutorService pool = Executors.newFixedThreadPool(taskSize);
// 创建多个有返回值的任务
List<Future> list = new ArrayList<Future>();
for (int i = 0; i < taskSize; i++) {
Callable c = new ThredQuery(redisActiveTestsMapper);
// 执行任务并获取Future对象
Future f = pool.submit(c);
// System.out.println(">>>" + f.get().toString());
list.add(f);
}
// 关闭线程池
pool.shutdown();
// 获取所有并发任务的运行结果
for (Future f : list) {
// 从Future对象上获取任务的返回值，并输出到控制台
try {
String s = f.get().toString();
System.out.println(">>>" +s );
}catch (Exception e){
}
}
Date date2 = new Date();
System.out.println("----程序结束运行----，程序运行时间【" + (date2.getTime() - date1.getTime()) + "毫秒】");
return new ArrayList<>();
public class ThredQuery implements Callable<Object>
{
private RedisActiveTestsMapper redisActiveTestsMapper;
public ThredQuery(RedisActiveTestsMapper redisActiveTestsMapper) {
this.redisActiveTestsMapper = redisActiveTestsMapper;
}
@Override
public Object call() throws Exception {
int i=1;
System.out.println(">>>" + i + "任务启动");
Date dateTmp1 = new Date();
Thread.sleep(1000);
Date dateTmp2 = new Date();
long time = dateTmp2.getTime() - dateTmp1.getTime();
List<RedisActiveTests> selectnan = redisActiveTestsMapper.selectnan(new RedisActiveTests());
System.out.println(">>>" + i + "任务终止");
i++;
return JSONArray.toJSONString(selectnan) + "任务返回运行结果,当前任务时间【" + time + "毫秒】";
}
}