Data Access 2.0? Please welcome: Spring Data!

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Data Access 2.0? …please welcome… Spring Data! Oliver Gierke

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Oliver Gierke Spring Data Core/JPA/MongoDB [email protected] www.olivergierke.de olivergierke

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What to expect?

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Why? How? What?

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A Developer‘s View

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What to expect? NOT!

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What to expect? NOT!

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Retrospect

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Relational databases

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Scaling

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Data structures

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(No)SQL Redis Riak MongoDB Cassandra CouchDB Neo4J HBase SimpleDB OrientDB Membase Hibari Voldemort Sones

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Key Value

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Column families

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Graphs

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Documents

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No content

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Document database JSON documents JSON queries

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19 MongoDB Infrastructure API Mongo mongo = new Mongo(…); DB db = mongo.getDB("myDatabase"); Collection collection = db.getCollection("myCollection"); DBObject address = new BasicDBObject(); address.put("city", "London"); DBObject person = new BasicDBObject(); person.put("ﬁrstname", "Dave"); person.put("lastname", "Matthews"); person.put("address", address); collection.save(person);

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20 MongoDB Query API Mongo mongo = new Mongo(…); DB db = mongo.getDB("myDatabase"); Collection collection = db.getCollection("myCollection"); DBObject query = new BasicDBObject(); query.put("address.city", "London"); DBCursor cursor = collection.ﬁnd(query); for (DBObject element : cursor) { // Map data onto object }

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Graph database Nodes / Relationships Traversals / Cypher / Gremlin

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22 Neo4J Infrastructure API GraphDatabaseService database = new EmbeddedGraphDatabase(…); Transaction tx = database.beginTx(); try { Node mrAnderson = database.createNode(); mrAnderson.setProperty("name", "Thomas Anderson"); Node morpheus = database.createNode(); morpheus.setProperty("name", "Morpheus"); Relationship friendship = mrAnderson.createRelationshipTo( morpheus, FriendTypes.KNOWS); tx.success(); } ﬁnally { tx.ﬁnish(); }

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23 Neo4J Query API GraphDatabaseService database = new EmbeddedGraphDatabase(…); CypherParser parser = new CypherParser(); Query query = parser.parse("start person = Person(id = *) match " + "person-[:colleagues]->colleague where colleague.ﬁrstname = {name}"); Map parameters = new HashMap(); parameters.put("name", "Dave"); ExecutionEngine engine = new ExecutionEngine(database); ExecutionResult result = engine.execute(query, parameters); for (EntrySet element : result) { // Map data onto object }

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24 Neo4J entity class Actor { private ﬁnal Node node; public Actor(Node node) { … } public String getName() { return (String) node.getProperty(„name“); } … }

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Forest for the woods?

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JPA?

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" This document is the speciﬁcation of the Java API for the management of persistence and object/relational mapping with Java EE and Java SE. The technical objective of this work is to provide an object/relational mapping facility for the Java application developer using a Java domain model to man- age a relational database.

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JPA?

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There‘s some Spring for that!

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Spring Data

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"… provide a familiar and consistent Spring-based programming model while retaining store-speciﬁc features and capabilities.

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Spring Data JPA JDBC

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Spring Data JPA JDBC

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Spring Data JPA JDBC

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Spring Data JPA JDBC

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Building blocks

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Spring

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Mapping

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40 JPA entity mapping @Entity class Person { @Id @GeneratedValue(strategy=GenerationType.AUTO) private BigInteger id; private String ﬁrstname, lastname; @Column(name="email") private String emailAddress; @OneToMany private Set colleagues; }

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41 Entity mapping - MongoDB @Document class Person { @Id private BigInteger id; @Indexed private String firstname, lastname; @Field("email") private String emailAddress; @DBRef private Set colleagues; public Person(String firstname) { … } @PersistenceConstructor public Person(String firstname, String lastname) { … } … }

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42 Entity mapping - Neo4J @NodeEntity class Person { @GraphId private long id; @Indexed private String firstname, lastname; @RelatedTo(direction = Direction.INCOMING) private Set colleagues; public Person(String firstname) { … } @PersistenceConstructor public Person(String firstname, String lastname) { … } … }

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Templates

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44 MongoOperations / -Template public interface MongoOperations { // Generic callback-accepting methods T execute(DbCallback action); T execute(Class entityClass, CollectionCallback action); T execute(String collectionName, CollectionCallback action); // Higher level access methods List ﬁnd(Query query, Class entityClass); void save(Object objectToSave, String collectionName); WriteResult updateFirst(Query query, Update update, Class entityClass); // Geo API GeoResults geoNear(NearQuery near, Class entityClass); }

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45 MongoTemplate usage // Setup infrastructure Mongo mongo = new Mongo(); MongoDbFactory factory = new SimpleMongoDbFactory(mongo, „foo“); MongoTemplate template = new MongoTemplate(factory); // Create and save entity Person dave = new Person("Dave", "Matthews"); dave.setEmailAddress("[email protected]"); template.save(person); // Query entity Query query = new Query(new Criteria("emailAddress") .is("[email protected]")); assertThat(template.ﬁnd(query), is(dave));

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Repositories

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47 Repositories - JPA public interface PersonRepository extends Repository { // Finder for a single entity Person findByEmailAddress(String emailAddress); // Finder for multiple entities List findByLastnameLike(String lastname); // Finder with pagination Page findByFirstnameLike(String firstname, Pageable page); }

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48 Repositories - MongoDB public interface PersonRepository extends Repository { // Finder for a single entity Person findByEmailAddress(String emailAddress); // Finder for multiple entities List findByLastnameLike(String lastname); // Finder with pagination Page findByFirstnameLike(String firstname, Pageable page); // Geospatial queries List findByLocationNear(Point location, Distance distance); GeoResults findByLocationNear(Point location); }

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49 Repositories - MongoDB @Component public class MyClient { @Autowired private PersonRepository repository; public List doSomething() { Point point = new Point(43.7, 48.8); Distance distance = new Distance(200, Metrics.KILOMETERS); return repository.ﬁndByLocationNear(point, distance); } }

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50 Repositories - Neo4J interface PersonRepository extends GraphRepository // Finder for a single entity Person findByEmailAddress(String emailAddress); // Finder for multiple entities List findByLastnameLike(String lastname); // Finder with pagination Page findByFirstnameLike(String firstname, Pageable page); @Query("start person = Person(id = *) " + "match person-[:colleagues]->colleague where " + "colleague.firstname = {name}") List getPersonsWithColleaguesName( @Param("name") Movie m); }

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Repositories 51 Querydsl

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52 Querydsl QPerson $ = QPerson.person; BooleanExpression left = $.lastname.contains("eth"); BooleanExpression right = $.firstname.is("Carter"); public interface QueryDslPredicateExecutor { T findOne(Predicate predicate); List findAll(Predicate predicate); } public interface PersonRepository extends Repository, QueryDslPredicateExecutor { … } List result = repository.findAll(left.or(right)); assertThat(result.size(), is(2)); assertThat(result, hasItems(dave, carter));

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Wrap up

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Sophisticated mapping support Templates Repositories Querydsl Spring namespace Geospatial support (MongoDB) Cross-store persistence Wrap up

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Questions?

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Resources • www.springframework.org/spring-data • github.com/SpringSource/spring-data-mongodb • github.com/SpringSource/spring-data-neo4j • http://www.se-radio.net/2010/07/episode-165-nosql-and- mongodb-with-dwight-merriman • http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis