jpa 批量插入

@Override
@Transactional
public <S extends E> List<S> save(Iterable<S> entities) {
List<S> result = new ArrayList<>();
 if (entities == null) {
return result;
 }
Iterator<S> iterator = entities.iterator();
 int i = 0;
 int count = 0;
 //遍历循环 每20个(可以做成配置中读取) insert 批量插入一次库
 while (iterator.hasNext()) {
S entity = iterator.next();
 	entityManager.persist(entity);
 	result.add(entity);
	 i++;
 if (i % 20 == 0) {
entityManager.flush();
 	 entityManager.clear();
 count=0;
 }else {
count++;
 }
}
//判断 是否有剩余未flush的 最后flush
 if (count>0){
entityManager.flush();
 entityManager.clear();
 }
return result;
}

https://github.com/Alexey-/spring-boot-batch/blob/master/src/main/resources/application.properties