A Spring Data’s Guide to Persistence September 1–2, 2021 springone.io 1

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DON‘T PANIC Douglas Adams, The Hitchhiker's Guide to the Galaxy

4 SELECT e FROM employee e WHERE e.firstName = :name JPA create().select().from(EMPLOYEE) .where(EMPLOYEE.FIRST_NAME).eq(name) .fetch() JOOQ db.employee.find({ first_name : name }) NoSQL SELECT * FROM employee WHERE first_name = %1 SQL everything MATCH (n:Employee) WHERE n.firstName = ’...’ query: { match: { first_name: '...' } }

List findByFirstName(String name) Spring Data JPA JDBC Redis Neo4j R2DBC MongoDB ArangoDB Couchbase Cosmos DB yugabyteDB Elasticsearch Apache Geode Apache Cassandra ...

42 life – data - everything

7 A Familiar & Consistent Programming Model That Resprects Store Specific Traits no silver bullet no magic not one API to rule them all

The Basics

Anatomy 9 Entity Manager Database Driver Template API Mapping Conversion Resource & Transaction Management native store format <> domain type eg. enum -> string Default Implementation Repository Interface List findByFirstName(String name)

Template APIs 10 class MongoTemplate implements MongoOperations { List find(Query query, Class entityClass) List findAndRemove(Query query, Class entityClass) T execute(Class> entityClass, CollectionCallback callback) query(where(“firstName”).is(...)) template.execute(Employee.class, collection -> { return collection.find(new Document("firstname", "...")) .into(new ArrayList()); }); Access to native driver commands

Repositories 11 interface Repo extends ...{ Repository CrudRepository findAll(); findById(...) count(); save(...); delete(...); ... PagingAndSorting Repository findAll(Page); findAll(Sort); Proxy Default Implementation Store Specific List findAll(); long count(); Predefined methods List findByFirstName(String name); Derived Finder Method

Derived Queries 12 List findByFirstName(String name) Return Type Operation Keyword Match Against Bind Argument

Paging vs Streaming 13 Page findByFirstName(String name, Pageable page) Resource Allocation Per Invocation Stream findByFirstName(String name) Continuous Scrolling

Derived Fetch Queries 14 List findEmployeeByFirstNameLikeOrderByAgeAsc(String name) read get query search stream Placeholder For Anything You Like matches contains lessThan startsWith greaterThan isEmpty isNull isNotNull before after ... Match Operator Sort Direction Delimiter Employee Page Slice Stream

Derived Count | Exists Queries 15 int countEmployeeByFirstNameLike(String name) boolean existsEmployeeByFirstNameLike(String name)

Derived Delete Queries 16 @Modifying List deleteEmployeeByFirstNameLike(String name) remove Some Stores Need a Little Help void long Interested in the Operation Result?

17 I‘d far rather be happy than right any day. IDE Support Runtime Support Douglas Adams, The Hitchhiker's Guide to the Galaxy

Data Projections 18 List findByFirstName(String name) Closed Interface Projection interface View2 { String getFirstName(); String getLastName(); } class View1 { String firstName; String lastName; } DTO Projection interface View3 { @Value(“#{target....}”) String getName(); } Open Interface Projection Flexible View On Your Data

Query By Example 19 List findAll(Example probe) a Good Fit for Web Form Search Binding Page Stream long count Pageable Sort

Auditing 2 0 class Employee { String firstName; String lastName; @CreatedDate Instant created; @LastModifiedDate Instant lastModified; }

Reactive 21 Flux findByFirstName(String name) a Reactive Stream of Data For a moment, nothing happened. Then, after a second or so, nothing continued to happen. once you forget to subscribe to the stream Douglas Adams, The Hitchhiker's Guide to the Galaxy

Storage Engine Store Specific

23 class Employee { Long id; String firstName; String lastName; Manager manager; } class Manager { Long id; String name; List employees } ID Name 1000 Marvin ID FIRST_N LAST_N MANAGER_ID 1 Ford Perfect 1000 table based manager employee linking by default { _id : 1000, name : Marvin, employees : [ { id : 1, firstName : Ford, lastName : Perfect } ... document store embedding by default

2 4 Would it save you a lot of time if I just gave up and went mad now? Actually, it’s not that bad once you got the differences. Decide on what you need. Not what you got or think to be cool. Douglas Adams, The Hitchhiker's Guide to the Galaxy

25 @Entity class Employee { @Id @GeneratedValue(...) Long id; @Column(name="FIRST_N") String firstName; ... } @Document class Employee { @Id Long id; @Field(name=”first_n") String firstName; ... } JPA MongoDB

26 @Document class Manager { Long id; String name; @DBRef List employees } { _id : 1000, name : Marvin, employees : [ { $ref : employee, $id : 1 } ... native $dbref format MongoDB – Linking manager { _id : 1, ..., manager : 1000 } @Document class Employee { Long id; //... @DocumentReference Manager manager; } more common simple format employee

27 @Entity class Employee { Long id; //... @Embedded @AttributeOverrides({...}) Manager manager; } JPA – Embedding ID FIRST_N LAST_N MANAGER_ID MANAGER_NAME 1 Ford Perfect 1000 Marvin

Query Language Store Specific

Richer / Slimmer API 2 9 Read the Documentation for store specific features @Procedure(”Employee.increaseSalary”) Integer increaseSalary(Integer raise); JPA Stored Procedure call GeoResults findByOfficeLoactionNear(Point p, Distance max) List Stream MongoDB Geospatial Query

Native Queries 3 0 @Query(“SELECT m, COUNT(e) FROM Manager m JOIN m.employees e GROUP BY e.name”) List listManagerWithEmployeeCount(); JPA @Aggregation(“{ $project: { id : 1, name: 1, $size : employees } }”) List listManagerWithEmployeeCount(); MongoDB

Custom Implementations Store Specific

Repositories 3 2 interface Repo extends ...{ CrudRepository Repository PagingAndSorting Repository List findAll(); long count(); findAll(); findById(...) count(); save(...); delete(...); ... findAll(Page); findAll(Sort); Default Implementation Proxy Store Specific

Repository Fragments 3 3 interface Repo extends ...{ List findAll(); long count(); Default Implementation Proxy Repository CrudRepository PagingAndSorting Repository Fragment I Fragment II Fragment III Fragment Impl Custom Method Declaration invocation target

Time is an illusion. Lunchtime doubly so. 3 4 Bad Performance? Slow Queries? Keep calm and log Douglas Adams, The Hitchhiker's Guide to the Galaxy

Trouble Shooting 3 5 Repository Metrics Logfiles Network Stats Query Planners

Guides & Samples 3 6 spring.io/guides spring-projects/spring-data-examples

#springone @SpringOne So long, and thanks for all the fish. Douglas Adams, The Hitchhiker's Guide to the Galaxy Noooo - Wait, there’s more...! Mapping Conversion Auditing Event Listeners Entity Callbacks Transactions Live Coding Spring Data Queries to the End of the Persistence Universe