@Test
public void shouldAggregateEmptyCollection() {
Aggregation aggregation =
newAggregation( //
project("tags"), //
unwind("tags"), //
group("tags") //
.count()
.as("n"), //
project("n") //
.and("tag")
.previousOperation(), //
sort(DESC, "n") //
);
AggregationResults<TagCount> results =
mongoTemplate.aggregate(aggregation, INPUT_COLLECTION, TagCount.class);
assertThat(results, is(notNullValue()));
assertThat(results.getServerUsed(), is("/127.0.0.1:27017"));
List<TagCount> tagCount = results.getMappedResults();
assertThat(tagCount, is(notNullValue()));
assertThat(tagCount.size(), is(0));
}
@Test
public void shouldDetectResultMismatch() {
createTagDocuments();
Aggregation aggregation =
newAggregation( //
project("tags"), //
unwind("tags"), //
group("tags") //
.count()
.as("count"), // count field not present
limit(2) //
);
AggregationResults<TagCount> results =
mongoTemplate.aggregate(aggregation, INPUT_COLLECTION, TagCount.class);
assertThat(results, is(notNullValue()));
assertThat(results.getServerUsed(), is("/127.0.0.1:27017"));
List<TagCount> tagCount = results.getMappedResults();
assertThat(tagCount, is(notNullValue()));
assertThat(tagCount.size(), is(2));
assertTagCount(null, 0, tagCount.get(0));
assertTagCount(null, 0, tagCount.get(1));
}
@Test
public void shouldAggregate() {
createTagDocuments();
Aggregation agg =
newAggregation( //
project("tags"), //
unwind("tags"), //
group("tags") //
.count()
.as("n"), //
project("n") //
.and("tag")
.previousOperation(), //
sort(DESC, "n") //
);
AggregationResults<TagCount> results =
mongoTemplate.aggregate(agg, INPUT_COLLECTION, TagCount.class);
assertThat(results, is(notNullValue()));
assertThat(results.getServerUsed(), is("/127.0.0.1:27017"));
List<TagCount> tagCount = results.getMappedResults();
assertThat(tagCount, is(notNullValue()));
assertThat(tagCount.size(), is(3));
assertTagCount("spring", 3, tagCount.get(0));
assertTagCount("mongodb", 2, tagCount.get(1));
assertTagCount("nosql", 1, tagCount.get(2));
}