DATAMONGO-2153 - Polishing.
Use MongoQueryMethod.getDomainClass() instead of getRepositoryDomainType(). Simplify annotation presence indicator methods hasAnnotatedSort() and hasAnnotatedCollation(). Refactor getAnnotatedAggregation() to non-nullable method throwing IllegalStateException to be consistent with other getXxx() methods. Simplify aggregation execution and consider collection/single element declaration for reactive execution. Tweak docs. Original pull request: #743.
This commit is contained in:
Mark Paluch
@@ -1,11 +1,9 @@
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[[mongodb.repositories.queries.aggregation]]
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=== Aggregation Repository Methods
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The repository layer offers means interact with <<mongo.aggregation, the aggregation framework>> via annotated repository
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finder methods. Similar to the <<mongodb.repositories.queries.json-based, JSON based queries>> a pipeline can be defined
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via the `org.springframework.data.mongodb.repository.Aggregation` annotation. The definition may contain simple placeholders
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like `?0` as well as https://docs.spring.io/spring/docs/{springVersion}/spring-framework-reference/core.html#expressions[SpEL expressions]
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`?#{ ... }`.
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The repository layer offers means to interact with <<mongo.aggregation, the aggregation framework>> via annotated repository query methods.
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Similar to the <<mongodb.repositories.queries.json-based, JSON based queries>>, you can define a pipeline using the `org.springframework.data.mongodb.repository.Aggregation` annotation.
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The definition may contain simple placeholders like `?0` as well as https://docs.spring.io/spring/docs/{springVersion}/spring-framework-reference/core.html#expressions[SpEL expressions] `?#{ … }`.
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.Aggregating Repository Method
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====
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@@ -13,33 +11,37 @@ like `?0` as well as https://docs.spring.io/spring/docs/{springVersion}/spring-f
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----
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public interface PersonRepository extends CrudReppsitory<Person, String> {
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@Aggregation("{ $group: { _id : $lastname, names : { $addToSet : $?0 } } }")
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List<PersonAggregate> groupByLastnameAnd(String property); <1>
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@Aggregation("{ $group: { _id : $lastname, names : { $addToSet : $firstname } } }")
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List<PersonAggregate> groupByLastnameAndFirstnames(Sort sort); <2>
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List<PersonAggregate> groupByLastnameAndFirstnames(); <1>
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@Aggregation("{ $group: { _id : $lastname, names : { $addToSet : $firstname } } }")
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List<PersonAggregate> groupByLastnameAndFirstnames(Sort sort); <2>
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@Aggregation("{ $group: { _id : $lastname, names : { $addToSet : $?0 } } }")
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List<PersonAggregate> groupByLastnameAnd(String property, Pageable page); <3>
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List<PersonAggregate> groupByLastnameAnd(String property); <3>
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@Aggregation("{ $group: { _id : $lastname, names : { $addToSet : $?0 } } }")
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List<PersonAggregate> groupByLastnameAnd(String property, Pageable page); <4>
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@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
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SumValue sumAgeUsingValueWrapper(); <4>
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SumValue sumAgeUsingValueWrapper(); <5>
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@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
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Long sumAge(); <5>
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Long sumAge(); <6>
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@Aggregation("{ $group : { _id : null, total : { $sum : $age } } }")
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AggregationResults<SumValue> sumAgeRaw(); <6>
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AggregationResults<SumValue> sumAgeRaw(); <7>
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@Aggregation("{ '$project': { '_id' : '$lastname' } }")
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List<String> findAllLastnames(); <7>
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List<String> findAllLastnames(); <8>
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}
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----
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[source,java]
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----
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public class PersonAggregate {
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private @Id String lastname; <2>
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private @Id String lastname; <2>
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private List<String> names;
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public PersonAggregate(String lastname, List<String> names) {
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@@ -51,7 +53,7 @@ public class PersonAggregate {
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public class SumValue {
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private final Long total; <4> <6>
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private final Long total; <5> <7>
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public SumValue(Long total) {
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// ...
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@@ -60,30 +62,28 @@ public class SumValue {
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// Getter omitted
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}
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----
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<1> Replace `?0` with the given value for `property`.
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<2> If `Sort` argument is present, `$sort` is added at the pipelines tail so that it only affects the order of the final results
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after having passed all other aggregation stages. Therefore the `Sort` properties are mapped against the methods return type
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`PersonAggregate` which turns `Sort.by("lastname")` into `{ $sort : { '_id', 1 } }` because `PersonAggregate.lastname` is
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annotated with `@Id`.
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<3> `$skip`, `$limit` and `$sort` can be passed on via a `Pageable` argument. Same as in 2., the operators are applied at
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the pipelines tail.
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<4> Map the result of an aggregation returning a single `Document` to an instance of a desired `SumValue` target type.
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<5> Aggregations resulting in single document holding just an accumulation result like eg. `$sum` can be extracted directly from
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the result `Document`. To gain more control one might consider `AggregationResult` as the methods return type as shown in 4. or 6.
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<6> Obtain the raw `AggregationResults` mapped to the generic target wrapper type `SumValue` or `org.bson.Document`.
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<7> Like in (5) a single value can be directly obtained from mutliple result ``Document``s.
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<1> Aggregation pipeline to group first names by `lastname` in the `Person` collection returning these as `PersonAggregate`.
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<2> If `Sort` argument is present, `$sort` is appended after the declared pipeline stages so that it only affects the order of the final results after having passed all other aggregation stages.
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Therefore, the `Sort` properties are mapped against the methods return type `PersonAggregate` which turns `Sort.by("lastname")` into `{ $sort : { '_id', 1 } }` because `PersonAggregate.lastname` is annotated with `@Id`.
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<3> Replaces `?0` with the given value for `property` for a dynamic aggregation pipeline.
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<4> `$skip`, `$limit` and `$sort` can be passed on via a `Pageable` argument. Same as in <2>, the operators are appended to the pipeline definition.
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<5> Map the result of an aggregation returning a single `Document` to an instance of a desired `SumValue` target type.
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<6> Aggregations resulting in single document holding just an accumulation result like eg. `$sum` can be extracted directly from the result `Document`.
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To gain more control, you might consider `AggregationResult` as method return type as shown in <7>.
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<7> Obtain the raw `AggregationResults` mapped to the generic target wrapper type `SumValue` or `org.bson.Document`.
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<8> Like in <6>, a single value can be directly obtained from multiple result ``Document``s.
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====
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TIP: `@Aggregation` can also be used with <<mongo.reactive.repositories, Reactive Repositories>>.
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TIP: You can use `@Aggregation` also with <<mongo.reactive.repositories, Reactive Repositories>>.
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[NOTE]
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====
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Obtaining simple type single results inspects the returned `Document` and checks for the following
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Simple-type single-result inspects the returned `Document` and checks for the following:
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. Only one entry in the document, return it.
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. Two entries, one is the `_id` value. Return the other.
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. Return for the first value assignable to the return type.
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. Throw an execption if none of the above applied.
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. Throw an exception if none of the above is applicable.
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====
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WARNING: The `Page` return type is not supported for repository methods using `@Aggregation`. However you can use a
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