Spring mongodb aggregation

Spring mongodb aggregation DEFAULT

Pipeline Aggregation Operators

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Set Aggregation Operators

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Group Aggregation Operators

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Arithmetic Aggregation Operators

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String Aggregation Operators

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Comparison Aggregation Operators

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Array Aggregation Operators

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Literal Operators

Date Aggregation Operators

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Variable Operators

Conditional Aggregation Operators

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Type Aggregation Operators

Convert Aggregation Operators

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Object Aggregation Operators

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Sours: https://spring.getdocs.org/en-US/spring-data-docs/spring-data-mongodb/reference/mongo.core/mongo.aggregation.html

Overview:

In this tutorial, I would like to show how to use the MongoDB AggregationPipeline to process multiple documents and present the data in the desired format with ReactiveSpring Data MongoDB Repository and MongoDB Template.

Project Setup:

Lets first create a simple spring boot project with these dependencies.

Sample Application:

Let’s consider an application in which freelancers register themselves with their skill sets. The information is stored in the MongoDB as shown below.

Users of the application would like to see for each skill set/technology, all the available freelancers. So the UI expectation is more or less like this.

Let’s see how to achieve this using Spring Data.

MongoDB Setup:

I use docker-compose to set up MongoDB and insert above documents.

MongoDB Aggregation Pipeline:

MongoDB Aggregation Pipeline framework allows us to group multiple documents, process information and present in desired format. For our requirement, We need to have following stages in our aggregation pipeline.

  • unwind:  Each freelancer has an array of skill sets. It is stored in the skills field.This stage reconstructs the document in a way that a person with 3 skills would be presented as 3 persons with 1 skill each.
  • group: Once you have unwinded (!), now we could group by skills field. For each skill, extract the names and push it to an array!
  • project: Once we have grouped the records, then we need to look for the specific fields we are interested in. I exclude the _id and retrieve as skill, then I also need the names field.

Now let’s get this implemented.

Entity Class:

Our entity class is represented as shown below.

Projection Class:

Since we would like to present the data differently, Lets create a model class for that.

@Aggregation:

Reactive Spring Data MongoDB Repository:

Once we have our stages ready, we include them as a aggregation pipeline stages as the value for the @Aggregation. Do note that it returns the instances of projection class we have defined above.

Application Properties:

Demo:

At this point, everything seems to be ready! We can run and verify.

Output:

We get the list of skills and corresponding freelancers who can be hired.

Aggregation With Template:

Reactive Spring Data MongoDB Template:

Spring Data provides the support for the MongoDB Aggregation Pipeline framework via Mongo Template as well. We can create all the stages as shown here and get it executed.

Demo:

We would get the same output, If we modify the runner as shown below.

Summary:

We were able to successfully demonstrate the MongoDB Aggregation Pipeline using both Reactive Spring DataMongoDB Repository & Template.

The source code is available here.

Learn more about MongoDB + Reactive Spring Data here.

Happy learning 🙂

Sours: https://www.vinsguru.com/mongodb-aggregation-pipeline-reactive-spring-data/
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Sours: https://www.javaprogramto.com/2020/05/spring-boot-data-mongodb-projections-aggregations.html
O poder do MongoDB Aggregation Framework para Desenvolvedores

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Aggregation spring mongodb

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Spring Boot - Tutorial 27 : MongoClient with Aggregation, Projection, and Dynamic APIs

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