Conditional query with spring mongotemplate - spring

Question

I want to use conditional query.
Here is my query
db.projects.aggregate([
{
"$group": {
"_id": "$iecode",
"treatmentArms": { "$first": "$evaluationDTOList" }
}
},
{ "$unwind": "$treatmentArms" },
{
"$group": {
"_id": null,
"Package": {
"$sum": {
"$cond": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Package" ] },
1, 0
]
}
},
"Constraint-relaxing mechanisms": {
"$sum": {
"$cond": [
{
"$and": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
{ "$eq": [ "$treatmentArms.mechanismTested1", "Constraint-relaxing mechanisms" ] }
]
},
1,
0 ]
}
},
"Delivery mechanisms": {
"$sum": {
"$cond": [
{
"$and": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
{ "$eq": [ "$treatmentArms.mechanismTested1", "Delivery mechanisms" ] }
]
},
1,
0 ]
}
},
"Other": {
"$sum": {
"$cond": [
{
"$and": [
{ "$eq": [ "$treatmentArms.mechanismOrPkg", "Mechanism" ] },
{ "$eq": [ "$treatmentArms.mechanismTested1", "Other" ] }
]
},
1,
0 ]
}
}
}
}
])
Here is my java code
DBObject groupByIECode = new BasicDBObject("$group",
new BasicDBObject("_id", new BasicDBObject("iecode","$iecode")).append("treatmentArms",new BasicDBObject("$first","$evaluationDTOList")));
System.out.println("groupByIECode: "+groupByIECode.toString());
DBObject unwind = new BasicDBObject("$unwind","$treatmentArms");
System.out.println("unwind: "+unwind.toString());
DBObject finalCalculation = new BasicDBObject("$group",new BasicDBObject("_id",null))
.append(
"Package", new BasicDBObject(
"$sum", new BasicDBObject(
"$cond", new Object[]{
new BasicDBObject(
"$eq", new Object[]{ "$treatmentArms.mechanismOrPkg", "Package"}
),
1,
0
}
)
)
);
System.out.println("finalCalculation: "+finalCalculation);
final AggregationOutput output = projects.aggregate(match,groupByIECode,unwind,finalCalculation);
It gives me MongoException$DuplicateKey
Later I found out that $cond operator is not supported in spring mongotemplate. So how do I implememt this conditional query with spring mongotemplate.
This link has some explanation but it do not shows full implementation

Answer 1

From the documentation, a canonical example for using the Spring Data MongoDB support for the MongoDB Aggregation Framework looks as follows:
import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;
Aggregation agg = newAggregation(
pipelineOP1(),
pipelineOP2(),
pipelineOPn()
);
AggregationResults<OutputType> results = mongoTemplate.aggregate(agg,
"INPUT_COLLECTION_NAME", OutputType.class);
List<OutputType> mappedResult = results.getMappedResults();
Note that if you provide an input class as the first parameter to the
newAggregation method the MongoTemplate will derive the name of the
input collection from this class. Otherwise if you don’t specify
an input class you must provide the name of the input collection
explicitly. If an input-class and an input-collection is provided the
latter takes precedence.
For your query, create a workaround that implements the AggregationOperation interface to take in a DBObject that represents a single group operation in an aggregation pipeline with the $cond operator:
public class GroupAggregationOperation implements AggregationOperation {
private DBObject operation;
public GroupAggregationOperation (DBObject operation) {
this.operation = operation;
}
#Override
public DBObject toDBObject(AggregationOperationContext context) {
return context.getMappedObject(operation);
}
}
Then implement the $group operation as a DBObject in the aggregation pipeline that is the same as the one you have:
DBObject operation = (DBObject) new BasicDBObject("$group", new BasicDBObject("_id", null))
.append(
"Package", new BasicDBObject(
"$sum", new BasicDBObject(
"$cond", new Object[]{
new BasicDBObject(
"$eq", new Object[]{ "$treatmentArms.mechanismOrPkg", "Package"}
),
1,
0
}
)
)
);
which you can then use as:
import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;
GroupAggregationOperation groupOp = new GroupAggregationOperation(operation);
Aggregation agg = newAggregation(
group("iecode").first("treatmentArms").as("treatmentArms"),
unwind("treatmentArms"),
groupOp
);
AggregationResults<Entity> results = mongoTemplate.aggregate(agg, Entity.class);
List<Entity> entities = results.getMappedResults();