mongodb 根据_id 查询记录：
public Price queryPriceById(String id) throws Exception {
return mongoTemplate.findById(new ObjectId(id), Price.class, PRICE_COLLECTION);
}
根据集合中的某个字段查询：
public Price queryPriceByName(String name) throws Exception {
Price price = null;
price = mongoTemplate.findOne(new Query(Criteria.where("name").is(name)), Price.class, PRICE_COLLECTION);
return price;
}