如何将以下MongoDB查询转换为Java Spring应用程序要使用的查询？我找不到一种通过提供的lookup方法使用pipeline的方法。
这是我要转换的查询。我还想指出，我没有使用$unwind，因为我希望deliveryZipCodeTimings作为分组集合保留在返回对象中。
db.getCollection('fulfillmentChannel').aggregate([
{
$match: {
"dayOfWeek": "SOME_VARIABLE_STRING_1"
}
},
{
$lookup: {
from: "deliveryZipCodeTiming",
let: { location_id: "$fulfillmentLocationId" },
pipeline: [{
$match: {
$expr: {
$and: [
{$eq: ["$fulfillmentLocationId", "$$location_id"]},
{$eq: ["$zipCode", "SOME_VARIABLE_STRING_2"]}
]
}
}
},
{
$project: { _id: 0, zipCode: 1, cutoffTime: 1 }
}],
as: "deliveryZipCodeTimings"
}
},
{
$match: {
"deliveryZipCodeTimings": {$ne: []}
}
}
])
答案 0 :(得分：2)
基于@dnickless提供的信息，我能够解决此问题。我将发布完整的解决方案，希望将来对其他人有所帮助。
我正在使用mongodb-driver:3.6.4
首先，我必须创建一个自定义聚合操作类，以便可以传入自定义JSON mongodb查询以用于聚合操作。这将使我可以在pipeline内使用$lookup，而我使用的驱动程序版本不支持。{p>
public class CustomProjectAggregationOperation implements AggregationOperation {
private String jsonOperation;
public CustomProjectAggregationOperation(String jsonOperation) {
this.jsonOperation = jsonOperation;
}
@Override
public Document toDocument(AggregationOperationContext aggregationOperationContext) {
return aggregationOperationContext.getMappedObject(Document.parse(jsonOperation));
}
}
现在，我们可以将自定义JSON查询传递到我们的mongodb spring实现中，剩下的就是将这些值插入到TypedAggregation查询中。
public List<FulfillmentChannel> getFulfillmentChannels(
String SOME_VARIABLE_STRING_1,
String SOME_VARIABLE_STRING_2) {
AggregationOperation match = Aggregation.match(
Criteria.where("dayOfWeek").is(SOME_VARIABLE_STRING_1));
AggregationOperation match2 = Aggregation.match(
Criteria.where("deliveryZipCodeTimings").ne(Collections.EMPTY_LIST));
String query =
"{ $lookup: { " +
"from: 'deliveryZipCodeTiming'," +
"let: { location_id: '$fulfillmentLocationId' }," +
"pipeline: [{" +
"$match: {$expr: {$and: [" +
"{ $eq: ['$fulfillmentLocationId', '$$location_id']}," +
"{ $eq: ['$zipCode', '" + SOME_VARIABLE_STRING_2 + "']}]}}}," +
"{ $project: { _id: 0, zipCode: 1, cutoffTime: 1 } }]," +
"as: 'deliveryZipCodeTimings'}}";
TypedAggregation<FulfillmentChannel> aggregation = Aggregation.newAggregation(
FulfillmentChannel.class,
match,
new CustomProjectAggregationOperation(query),
match2
);
AggregationResults<FulfillmentChannel> results =
mongoTemplate.aggregate(aggregation, FulfillmentChannel.class);
return results.getMappedResults();
}
答案 1 :(得分：1)
驱动程序几乎总是落后于MongoDB提供的当前语言功能-因此，尚无法通过API很好地访问某些最新和最出色的功能。恐怕这是其中一种情况，您将需要使用字符串。有点像这样（未经测试）：
AggregationOperation match = Aggregation.match(Criteria.where("dayOfWeek").is("SOME_VARIABLE_STRING_1"));
AggregationOperation match2 = Aggregation.match(Criteria.where("deliveryZipCodeTimings").ne([]));
String query = "{ $lookup: { from: 'deliveryZipCodeTiming', let: { location_id: '$fulfillmentLocationId' }, pipeline: [{ $match: { $expr: { $and: [ { $eq: ['$fulfillmentLocationId', '$$location_id']}, { $eq: ['$zipCode', 'SOME_VARIABLE_STRING_2']} ]} } }, { $project: { _id: 0, zipCode: 1, cutoffTime: 1 } }], as: 'deliveryZipCodeTimings' } }";
Aggregation.newAggregation(match, (DBObject) JSON.parse(query), match2);
答案 2 :(得分：1)
我想添加我的解决方案，该解决方案在某些方面重复了以前发布的解决方案。
对于Mongo驱动程序v3.x，我采用以下解决方案：
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import com.mongodb.BasicDBList;
import com.mongodb.BasicDBObject;
import com.mongodb.util.JSON;
import org.bson.Document;
import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
public class JsonOperation implements AggregationOperation {
private List<Document> documents;
public JsonOperation(String json) {
Object root = JSON.parse(json);
documents = root instanceof BasicDBObject
? Collections.singletonList(new Document(((BasicDBObject) root).toMap()))
: ((BasicDBList) root).stream().map(item -> new Document((Map<String, Object>) ((BasicDBObject) item).toMap())).collect(Collectors.toList());
}
@Override
public Document toDocument(AggregationOperationContext context) {
// Not necessary to return anything as we override toPipelineStages():
return null;
}
@Override
public List<Document> toPipelineStages(AggregationOperationContext context) {
return documents;
}
}
，然后假设在某些资源aggregations.json中给出了聚合步骤：
[
{
$match: {
"userId": "..."
}
},
{
$lookup: {
let: {
...
},
from: "another_collection",
pipeline: [
...
],
as: "things"
}
},
{
$sort: {
"date": 1
}
}
]
一个人可以如下使用上述类：
import static org.springframework.data.mongodb.core.aggregation.Aggregation.newAggregation;
Collection<ResultDao> results = mongoTemplate.aggregate(newAggregation(new JsonOperation(resourceToString("aggregations.json", StandardCharsets.UTF_8))), "some_collection", ResultDao.class).getMappedResults();
由于JSON类已从Mongo v4中删除，我将类重写如下：
import java.util.Collections;
import java.util.List;
import org.bson.Document;
import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
public class JsonOperation implements AggregationOperation {
private List<Document> documents;
private static final String DUMMY_KEY = "dummy";
public JsonOperation(String json) {
documents = parseJson(json);
}
static final List<Document> parseJson(String json) {
return (json.startsWith("["))
? Document.parse("{\"" + DUMMY_KEY + "\": " + json + "}").getList(DUMMY_KEY, Document.class)
: Collections.singletonList(Document.parse(json));
}
@Override
public Document toDocument(AggregationOperationContext context) {
// Not necessary to return anything as we override toPipelineStages():
return null;
}
@Override
public List<Document> toPipelineStages(AggregationOperationContext context) {
return documents;
}
}
但是由于字符串操作，现在的实现有点难看。如果有人对如何以更优雅的方式解析对象数组有更好的主意，请编辑这篇文章或发表评论。理想情况下，Mongo核心中应该有一些方法可以解析JSON对象或列表（返回BasicDBObject / BasicDBList或Document / List<Document>）。
我还跳过了用Document方法转换toPipelineStages()实例的步骤，因为在我的情况下这是不必要的：
@Override
public List<Document> toPipelineStages(AggregationOperationContext context) {
return documents.stream().map(document -> context.getMappedObject(document)).collect(Collectors.toList());
}
答案 3 :(得分：0)
当我使用已接受答案中解释的方式时，我遇到了一些 JSON 解析异常，因此我深入挖掘了默认的 MongoDB java 驱动程序（版本 3）文档类来构建聚合查询，并发现可以构建任何聚合查询如下，
按如下方式替换mongo控制台查询中的每个元素
AggregationOperation customLookupOperation = new AggregationOperation() {
@Override
public Document toDocument(AggregationOperationContext context) {
return new Document(
"$lookup",
new Document("from", "deliveryZipCodeTiming")
.append("let",new Document("location_id", "$fulfillmentLocationId"))
.append("pipeline", Arrays.<Object> asList(
new Document("$match", new Document("$expr", new Document("$and",
Arrays.<Object>asList(
new Document("$eq", Arrays.<Object>asList("$fulfillmentLocationId", "$$location_id")),
new Document("$eq", Arrays.<Object>asList("$zipCode", "SOME_VARIABLE_STRING_2"))
)))),
new Document("$project", new Document("_id",0).append("zipCode", 1)
.append("cutoffTime", 1)
)
))
.append("as", "deliveryZipCodeTimings")
);
}
};
终于可以在聚合管道中使用聚合操作了，
Aggregation aggregation = Aggregation.newAggregation(matchOperation,customLookupOperation,matchOperation2);