/** Creates each document for pipeline with instances of Bson documents */
private void fromBsonDocuments() {
Document totalPop =
new Document()
.append(
"$group",
new Document()
.append("_id", "$state")
.append("totalPop", new Document("$sum", "$pop")));
Document gtOneMillion =
new Document().append("$match", new Document("totalPop", new Document("$gte", 1000000)));
//
// Compose aggregation pipeline
List<Document> pipeline = Arrays.asList(totalPop, gtOneMillion);
//
// Executes aggregation query
List<Document> results =
DBHelper.getZipCodesCollection().aggregate(pipeline).into(new ArrayList<Document>());
//
// Display aggregation results
System.out.println("\nStates with population greater than one million");
for (Document result : results) {
System.out.println(result.toJson());
}
}
/** Creates each document for pipeline using helper classes included in driver */
private void fromHelperClasses() {
Bson totalPop = Aggregates.group("$state", Accumulators.sum("totalPop", "$pop"));
Bson gtOneMillion = Aggregates.match(Filters.gte("totalPop", 1000000));
//
// Compose aggregation pipeline
List<Bson> pipeline = Arrays.asList(totalPop, gtOneMillion);
//
// Executes aggregation query
List<Document> results =
DBHelper.getZipCodesCollection().aggregate(pipeline).into(new ArrayList<Document>());
//
// Display aggregation results
System.out.println("\nStates with population greater than one million");
for (Document result : results) {
System.out.println(result.toJson());
}
}
/** Parse a raw string into json for the aggregation framework */
private void fromRawString() {
String totalPop = "{ $group: { _id: \"$state\", totalPop: { $sum: \"$pop\"}}}";
String gtOneMillion = "{ $match: { totalPop: {$gte: 1000000}}}";
//
// Compose aggregation pipeline
List<Document> pipeline = Arrays.asList(Document.parse(totalPop), Document.parse(gtOneMillion));
//
// Executes aggregation query
List<Document> results =
DBHelper.getZipCodesCollection().aggregate(pipeline).into(new ArrayList<Document>());
//
// Display aggregation results
System.out.println("\nStates with population greater than one million");
for (Document result : results) {
System.out.println(result.toJson());
}
}