在mongodb中找到与集合不同的对象 [英] Finding distinct from collections in mongodb

问题描述

我们先前用于从集合中查找不同元素的实现曾经是:

Our previous implementation for finding distinct elements from a collection used to be :

List<String> names = mongoClient.getDB(dbName).getCollection(collectionName).distinct(NAME_KEY);

尝试将其升级到使用mongo 3.3.0+的当前实现是:

Trying to upgrade this into the current implementation with mongo 3.3.0+ as tried is :

List<String> names = mongoClient.getDatabase(dbName)
                        .getCollection(collectionName, TDocType.class)
                        .distinct(NAME_KEY, String.class); // compile error - required Class<TResult> 

也尝试过

.distinct(NAME_KEY, TDocType.class)  // doesn't work                      

在这种情况下，迭代器的目标类型是什么?

What shall be the target type of the iterable in this case?

编辑 -问题不是

Edit - The question is not a duplicate of Get distinct records values since the implementation has changed over the upgrade of mongodb-java-driver.

推荐答案

您可以尝试类似的方法.

You can try something like this.

DistinctIterable<String> iterable = mongoClient.getDatabase(dbName).
            .getCollection(collectionName, TDocType.class).distinct(NAME_KEY, String.class);
MongoCursor<String> cursor = iterable.iterator();
List<String> list = new ArrayList<>();
while (cursor.hasNext()) {
    list.add(cursor.next());
 }

这篇关于在mongodb中找到与集合不同的对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！