MongoDB with Spring Data: A Practical Guide

MongoDB with Spring Data: A Practical Guide

Spring Data MongoDB makes it easy to persist Java objects to MongoDB without writing a single query.

Add the dependency

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

Define your document

@Document("articles")
public class Article {
    @Id
    private String id;

    @Indexed(unique = true)
    private String slug;

    private String title;
    private String content;

    @CreatedDate
    private Instant createdAt;

    @LastModifiedDate
    private Instant updatedAt;
}

Create a repository

public interface ArticleRepository extends MongoRepository<Article, String> {
    Optional<Article> findBySlug(String slug);
    List<Article> findByTitleContainingIgnoreCase(String keyword);
    Page<Article> findByStatus(PublishStatus status, Pageable pageable);
}

Spring Data generates the query from the method name — no JPQL, no Mongo query shell needed.

Compound indexes

@Document("articles")
@CompoundIndexes({
    @CompoundIndex(def = "{'status': 1, 'publishedAt': -1}"),
    @CompoundIndex(def = "{'category': 1, 'status': 1}")
})
public class Article { ... }

Custom aggregation

Aggregation agg = Aggregation.newAggregation(
    Aggregation.match(Criteria.where("status").is("PUBLISHED")),
    Aggregation.group("category").count().as("total"),
    Aggregation.sort(Sort.by(Sort.Direction.DESC, "total"))
);
List<CategoryCount> results = mongoTemplate.aggregate(agg, "articles", CategoryCount.class).getMappedResults();