Customizing Individual Repositories in Spring Data

Spring Data provides various options to create query methods with little coding. However, when those options don’t fit your needs, you can provide your own custom implementation for repository methods. This section describes how to do that.

Customizing Repositories

To add custom functionality to a repository, follow these steps:

1. Define a Fragment Interface: Create an interface for the custom functionality.
2. Implement the Fragment Interface: Provide the implementation for the custom functionality.
3. Extend the Fragment Interface: Make your repository interface extend the fragment interface.

1. Define a Fragment Interface

Create an interface with custom methods for your repository. Here is the example from our SalesCustomRepository.java:

package com.mongodb.quickstart.repositories;

import java.util.List;
import com.mongodb.quickstart.dtos.*;

public interface SalesCustomRepository {
    List<TotalSalesByLocationDTO> calculateTotalSalesByLocation();
    List<AverageItemPricePerStoreDTO> averageItemPricePerStore();
    List<DistinctCustomersCountDTO> countDistinctCustomersByLocation();
    List<SalesByDayOfWeekDTO> totalSalesByDayOfWeek();
    List<SalesPerformanceDTO> compareSalesWithAndWithoutCoupons();
    List<RevenueByLocationDTO> calculateTotalRevenueByLocation();
    List<CustomerSatisfactionDTO> averageCustomerSatisfactionByLocation();
}

2. Implement the Fragment Interface

Create a class that implements the custom interface. This is just a snippet from our SalesCustomRepositoryImpl.java class:

package com.mongodb.quickstart.repositories;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Primary;
import org.springframework.data.domain.Sort;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.aggregation.*;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.stereotype.Repository;
import com.mongodb.quickstart.dtos.*;

import java.util.List;

@Repository
@Primary
public class SalesCustomRepositoryImpl implements SalesCustomRepository {

    @Autowired
    private MongoTemplate mongoTemplate;

    // Implementation of custom methods

    @Override
    public List<TotalSalesByLocationDTO> calculateTotalSalesByLocation() {
        GroupOperation groupStage = Aggregation.group("storeLocation").count().as("totalSales");
        Aggregation aggregation = Aggregation.newAggregation(groupStage);
        AggregationResults<TotalSalesByLocationDTO> results = mongoTemplate.aggregate(aggregation, "sales", TotalSalesByLocationDTO.class);
        return results.getMappedResults();
    }

    ...
}

3. Extend the Fragment Interface

Make your repository interface extend the fragment interface to combine the CRUD and custom functionality. By adding ∂our reference to our custom repository we are able to use the methods created in both, allowing us to add methods that utilize MongoTemplate with MongoRepository.

package com.mongodb.quickstart.repositories;

import org.springframework.data.mongodb.repository.MongoRepository;
import com.mongodb.quickstart.models.Sale;
import org.springframework.stereotype.Repository;

@Repository
public interface SalesRepository extends MongoRepository<Sale, String>, SalesCustomRepository {
    // Declare query methods here if needed
}

Key Points

1. Fragment Interface: Create an interface for the custom methods.
2. Fragment Implementation: Implement the interface in a class with the Impl suffix.
3. Extend the Repository Interface: Extend the fragment interface in your repository to combine CRUD and custom functionality.