Building Spring Data with MongoDB

copyright 2013 Trainologic LTD

Spring Data and MongoDBSpring Data and MongoDB

2copyright 2013 Trainologic LTD

Spring DataSpring Data

•Spring Data provides a set of utilities for working with NoSQL databases.

• It also provides support for relational databases and REST interfaces.

•We are going to focus over MongoDB support.

•But first, some basics…

Spring Data

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•Spring Data Commons provides a common API for the different Spring Data subprojects.

•The main interface in Spring Data is the Repository interface.

•This is a marker interface that is mainly used for discovering extending classes.

Data Commons

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•The main interface that extends from Repository is the CrudRepository one.

• It provides methods for saving, deleting, counting and retrieving of your domain class.

•Usually a specific storage technology class will be available that extends this one (e.g., MongoRepository).

•The PagingAndSortingRepository interface provides paging and sorting capabilities.

CrudRepository

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• If you don’t feel like exposing the entire CrudRepository interface, you can annotate your class with the @RepositoryDefinition annotation.

•Then, you can selectively provides the required methods.

Custom Repositories

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•Spring Data provides a mechanism for generating custom queries for your storage technology.

•A four steps recipe:

1. Define an interface that extends from the appropriate repository interface.

2. Add your query signatures.

3. Instruct Spring to create proxy for your repository.

4. Inject the generated bean and use it.

Custom Queries

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Example

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public interface MyCompanyRepository extends MongoRepository<Company,

String>{List<Company> findByCompanyName(String name);

}



•Spring Data can construct the actual query according to the method name or by additional declaration.

• If selecting the method name way then:

•The ‘By’ acts as a separator.

• Inherent support for And and Or.

•Support for Between, LessThan, GreaterThan and Like.

•Support IgnoreCase.

•And OrderBy with additional Asc or Desc.

Query Syntax

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•Query methods can also accept additional special parameters of the following types:

•Sort – allows to configure a sort operation.

•Pageable – allows to configure paging.

Query Syntax

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• In order to connect your Spring project to MongoDB, you need to create a connection.

•Can be done with either annotations or XML namespace (as usual in Spring).

•XML Schema example:

Connecting to MongoDB

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<mongo:mongo replica-set="127.0.0.1:27017,localhost:27018"> <mongo:options connections-per-host="8" threads-allowed-to-block-for-connection-multiplier="4"

connect-timeout="1000“ auto-connect-retry="true

slave-ok="true write-fsync="true"/>

</mongo:mongo/>



•MongoDB is a very popular NoSQL Database.

•Spring Data provides many features for easing (the already easy) programming to MongoDB.

•Two main features:

•MongoTemplate.

•Mongo Repositories.

Spring Data for MongoDB

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•As usual in Spring, template objects are both thread-safe and stateless.

•MongoTemplate provides API resembles as possible the native MongoDB driver for Java.

•The main difference is that the MongoTemplate can receive your model objects directly and not only DBObject.

•Your objects are mapped/converted to MongoDB objects.

MongoTemplate

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•You can configure your MongoTemplate with a WriteConcernResolver which will allow you to specify a write-concern on a per operation basis.

MongoTemplate

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• Id mapping is handled as follows:

•Usage of the @Id annotation (not the JPA one).

•A property/field named ‘id’.

• If you don’t define one, the framework will generate an id for you.

Id

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•The following annotations are provided for mapping:

•@Document, @DBRef, @Indexed, @CompoundIndex, @GeoSpatialIndexed, @Transient, @PersistenceConstructor, @Value, @Field

Supported Domain Mapping

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findAndModify as an Example

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•findAndModify receives a query object and an Update object and allows you to perform the famous search&update in MongoDB.



Querying

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•You can construct a query object using the following ways:

•Use Criteria statements.

•Use the BasicQuery object to provide plain ole’ JSON.



Querying

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• If you want to customize the query in a JSON way, you can use the @Query annotation.

•E.g.:

@Query(value="{ ‘lastName' : ?0 }", fields="{ 'firstName' : 1, 'lastName' : 1}") List<Student> findStudentsByLastName(String lastName);



Typesafe Queries

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•You can also perform typesafe queries with the Query DSL.

•However, in order to use it, you should generate DSL code using APT (resembles typed criteria model from JPA 2.0).

Technology

Building Spring Data with MongoDB