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Spring Abstracts is a aerial akin SpringSource activity whose purpose is to arrange and affluence the admission to altered kinds of chain stores, both relational database systems and NoSQL abstracts stores.

With every affectionate of chain store, your repositories (a.k.a. DAOs, or Abstracts Admission Objects) about action CRUD (Create-Read-Update-Delete ) operations on distinct area objects, finder methods, allocation and pagination. Spring Abstracts provides all-encompassing interfaces for these aspects (CrudRepository, PagingAndSortingRepository) as able-bodied as chain abundance specific implementations.

You may accept already acclimated one of the Spring arrangement altar (like JdbcTemplate) to address your custom athenaeum implementations. While the arrangement altar are powerful, we can do better. With Spring Data’s repositories, you charge alone to address an interface with finder methods authentic according to a accustomed set of conventions (which may alter depending on the affectionate of chain abundance you are using). Spring Abstracts will accommodate an adapted accomplishing of that interface at runtime. As an example:

Throughout this commodity we will analyze three of the sub projects for JPA, MongoDB and Neo4j. JPA is allotment of the JEE assemblage and defines a unified API for accessing relational databases and assuming O/R mapping. MongoDB is a scalable, high-performance, accessible source, document-oriented database. Neo4j is a blueprint database, a absolutely transactional database that food abstracts structured as graphs.

All these Spring Abstracts projects abutment the followings aspects:

Other Spring Abstracts projects like Spring Abstracts Redis or Spring Abstracts Riak about accommodate alone templates, because the agnate datastores abide baggy abstracts that cannot be mapped or queried.

Let’s accept a abundant attending at templates, commodity mapping and athenaeum support.

The capital purpose of a Spring Abstracts arrangement (and all added Spring templates) is ability allocation and barring translation.

In our case a ability is a datastore, which is generally accessed accidentally over a TCP/IP connection. The afterward archetype shows how to configure a MongoDB template:

First we ascertain some affectionate of affiliation factory, which is again referenced by the MongoTemplate. In the case of MongoDB, the Spring Abstracts activity depends on the low akin MongoDB Java driver.

In general, such a low akin datastore API will accept its own barring administration strategy. The Spring way of administration exceptions it to use absolved exceptions that the developer can catch, but does not accept to. To arch that gap, a arrangement accomplishing catches the low akin exceptions and rethrows a agnate absolved Spring exception, which is a bracket of Spring’s DataAccessException.

A arrangement offers abundance specific operations like saving, afterlight and deleting a distinct almanac or for active queries or map/reduce jobs. But all these methods assignment alone for the agnate basal datastore.

Spring Abstracts JPA does not action a template, back the JPA accomplishing itself is already an absorption band on top of the JDBC API. JPA’s EntityManager is the analogue of a template. Barring adaptation is handled by the athenaeum implementation.

JPA alien a accepted for O/R mapping (i.e. mapping commodity graphs to relational database tables). Hibernate is apparently the best accepted O/R mapper that accouterments the JPA specification.

With Spring Data, this abutment is continued to NoSQL datastores with object-like abstracts structures. But these abstracts structures can be absolutely altered from anniversary other, so it would be difficult to accomplish up a accepted API for object/datastore mapping. Anniversary blazon of datastore comes with its own set of annotations to accommodate the bare meta advice for the mapping. Let’s see how a simple area commodity User may be mapped to our datastores:

JPA

MongoDB

Neo4j

If you are accustomed with JPA entities you will admit the accepted JPA annotations. Spring Abstracts reuses them; no added annotations are introduced. The mapping itself is done by the JPA accomplishing you are using. MongoDB and Neo4j crave a agnate set of annotations. You accept one at the chic akin to map the chic to a accumulating (in MongoDB a accumulating is agnate to a table in a relational database) or to a bulge blazon (nodes and edges are the capital abstracts types of a blueprint database like Neo4j).

Each JPA commodity has to accept a altered identifier. The aforementioned is accurate for MongoDB abstracts and Neo4j nodes.

MongoDB uses an @Id comment (not the aforementioned as JPA, it’s in the amalgamation org.springframework.data.annotation), Neo4j @GraphId. The ethics of these attributes are abounding afterwards constant the area object. For added assiduous attributes, you use the @Field comment if the aspect name in the MongoDB certificate does not bout the Java attribute.

References to added altar are additionally supported. The roles of our user can be persisted this way:

JPA

MongoDB

Neo4j

With JPA you use a @OneToMany relationship, the n ancillary is stored in addition table and usually queried with a join. MongoDB does not abutment joins amid collections, referenced altar are stored in-place aural the aforementioned certificate by default. You can accept references to added abstracts as able-bodied which aftereffect in a client-side join. In Neo4j relationships are alarm edges, which are one of the basal abstracts types.

To sum things up: MongoDB and Neo4j use an commodity mappings that is agnate to the able-bodied accepted JPA O/R mapping, but it is not absolutely the aforementioned because of the altered abstracts structures. The absorption abaft all of the mappings is the aforementioned though: map Java altar to the abstracts structures of your chain store.

If you accept anytime persisted abstracts in your business application, you apparently wrote some affectionate of DAO. Usually you apparatus the CRUD operations for distinct annal and a agglomeration of finder methods for anniversary assiduous class. Finder methods booty ambit that are put into your concern afore you assassinate them.

With the appearance of JPA, at atomic the CRUD operations are accessible through the EntityManager interface. Writing custom finders is still arid though: actualize a called query, set anniversary parameter, assassinate that query. For example:

This can be hardly bargain by appliance the chatty interface of a TypedQuery ...

... but still you are implementing a adjustment that calls setters and executes the concern for anniversary and every query. With Spring Abstracts JPA the aforementioned concern comes bottomward to the afterward allotment of code:

With Spring Abstracts JPA, JPQL queries don’t accept to be declared as @NamedQuerys in the chic book of the agnate JPA entity. Instead a concern is an comment of the athenaeum method(!):

All the aloft additionally holds accurate for Spring Abstracts MongoDB and Spring Abstracts Neo4j. The afterward archetype queries a Neo4j database with the Cipher concern language:

Of course, the allotment conventions of the finder methods alter from chain abundance to chain store. For example, MongoDB supports geospatial queries and appropriately you can address queries like this:

There is additionally all-encompassing abutment for paging and sorting, by accouterment appropriate ambit to the finder methods for all chain stores.

The capital advantages of athenaeum abutment are:

This commodity gives an overview of a lot of circuitous technologies and tries to ascertain similarities and differences. For a added abundant appearance of the Spring Abstracts projects, I acclaim demography a attending at the projects’ homepages:

To acknowledgment the catechism accustomed in the headline: no, there is no accepted API to all the chain stores. The differences are too fundamental. But the Spring Abstracts activity does accommodate a accepted programming archetypal to admission your data:

The athenaeum abutment is an absorption from the concrete abstracts band and additionally makes it actual accessible to address a lot of finder methods. With the commodity mapping, your area commodity can be adapted into the abstracts types of your chain store. The templates accommodate low akin admission to abundance specific capabilities.

Tobias Trelle is a chief IT adviser at codecentric AG, with over 15 years of acquaintance in the IT business. His capital interests are software architectures, EAI and billow computing. A approved blogger, he additionally provides training and gives talks at conferences.Twitter/Blog/Linked In/G

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