[英]How to use $concat with a $cond with MongoDB Java drivers
[英]How to use MongoTemplate cond and filter in java code?
這是來自 MongoDB 手冊的示例,用於$filter聚合轉換為 Spring 數據 MongoDB 代碼。 相同的語法可以應用於有關使用$filter
和condition的問題。
MongoOperations mongoOps = new MongoTemplate(MongoClients.create(), "test");
Aggregation agg = newAggregation(
project()
.and(filter("items")
.as("item")
.by(Gte.valueOf("item.price").greaterThanEqualToValue(100)))
.as("items")
);
AggregationResults<Document> results = mongoOps.aggregate(agg, "sales", Document.class);
results.forEach(doc -> System.out.println(doc.toJson()));
參考: org.springframework.data.mongodb.core.aggregation.ArrayOperators.Filter 。
如果您使用Java 8和Spring 數據 MongoDB 3.0.3.RELEASE ,則這是針對您的問題的特定代碼。
import static org.springframework.data.mongodb.core.aggregation.Aggregation.match;
import static org.springframework.data.mongodb.core.aggregation.Aggregation.project;
import static org.springframework.data.mongodb.core.aggregation.ArrayOperators.Filter.filter;
import static org.springframework.data.mongodb.core.query.Criteria.where;
MongoOperations mongoOps = new MongoTemplate(MongoClients.create(), "database");
ProjectionOperation projectionOperation = project().and(filter("fields")
.as("field")
.by(Eq.valueOf("field.code").equalToValue("EngName")))
.as("fields");
MatchOperation matchOperation = match(where("fields.value").in("A","B"));
Aggregation agg = Aggregation.newAggregation(projectionOperation,matchOperation);
AggregationResults<Document> docs = mongoOps.aggregate(agg, "collection", Document.class);
docs.forEach(doc->System.out.println(doc));
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