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Preface

Spring Data JDBC offers a repository abstraction based on JDBC.

Project Metadata

1. New & Noteworthy

This section covers the significant changes for each version.

1.1. What’s New in Spring Data JDBC 2.0

  • Optimistic Locking support.

  • Support for PagingAndSortingRepository.

  • Query Derivation.

  • Full Support for H2.

  • All SQL identifiers know get quoted by default.

  • Missing columns no longer cause exceptions.

1.2. What’s New in Spring Data JDBC 1.1

  • @Embedded entities support.

  • Store byte[] as BINARY.

  • Dedicated insert method in the JdbcAggregateTemplate.

  • Read only property support.

1.3. What’s New in Spring Data JDBC 1.0

  • Basic support for CrudRepository.

  • @Query support.

  • MyBatis support.

  • Id generation.

  • Event support.

  • Auditing.

  • CustomConversions.

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Reference Documentation

2. JDBC Repositories

This chapter points out the specialties for repository support for JDBC. This builds on the core repository support explained in [repositories]. You should have a sound understanding of the basic concepts explained there.

2.1. Why Spring Data JDBC?

The main persistence API for relational databases in the Java world is certainly JPA, which has its own Spring Data module. Why is there another one?

JPA does a lot of things in order to help the developer. Among other things, it tracks changes to entities. It does lazy loading for you. It lets you map a wide array of object constructs to an equally wide array of database designs.

This is great and makes a lot of things really easy. Just take a look at a basic JPA tutorial. But it often gets really confusing as to why JPA does a certain thing. Also, things that are really simple conceptually get rather difficult with JPA.

Spring Data JDBC aims to be much simpler conceptually, by embracing the following design decisions:

  • If you load an entity, SQL statements get executed. Once this is done, you have a completely loaded entity. No lazy loading or caching is done.

  • If you save an entity, it gets saved. If you do not, it does not. There is no dirty tracking and no session.

  • There is a simple model of how to map entities to tables. It probably only works for rather simple cases. If you do not like that, you should code your own strategy. Spring Data JDBC offers only very limited support for customizing the strategy with annotations.

2.2. Domain Driven Design and Relational Databases.

All Spring Data modules are inspired by the concepts of “repository”, “aggregate”, and “aggregate root” from Domain Driven Design. These are possibly even more important for Spring Data JDBC, because they are, to some extent, contrary to normal practice when working with relational databases.

An aggregate is a group of entities that is guaranteed to be consistent between atomic changes to it. A classic example is an Order with OrderItems. A property on Order (for example, numberOfItems is consistent with the actual number of OrderItems) remains consistent as changes are made.

References across aggregates are not guaranteed to be consistent at all times. They are guaranteed to become consistent eventually.

Each aggregate has exactly one aggregate root, which is one of the entities of the aggregate. The aggregate gets manipulated only through methods on that aggregate root. These are the atomic changes mentioned earlier.

A repository is an abstraction over a persistent store that looks like a collection of all the aggregates of a certain type. For Spring Data in general, this means you want to have one Repository per aggregate root. In addition, for Spring Data JDBC this means that all entities reachable from an aggregate root are considered to be part of that aggregate root. Spring Data JDBC assumes that only the aggregate has a foreign key to a table storing non-root entities of the aggregate and no other entity points toward non-root entities.

In the current implementation, entities referenced from an aggregate root are deleted and recreated by Spring Data JDBC.

You can overwrite the repository methods with implementations that match your style of working and designing your database.

2.3. Annotation-based Configuration

The Spring Data JDBC repositories support can be activated by an annotation through Java configuration, as the following example shows:

Example 1. Spring Data JDBC repositories using Java configuration
@Configuration
@EnableJdbcRepositories                                                                (1)
class ApplicationConfig extends AbstractJdbcConfiguration {                            (2)

    @Bean
    public DataSource dataSource() {                                                   (3)

        EmbeddedDatabaseBuilder builder = new EmbeddedDatabaseBuilder();
        return builder.setType(EmbeddedDatabaseType.HSQL).build();
    }

    @Bean
    NamedParameterJdbcOperations namedParameterJdbcOperations(DataSource dataSource) { (4)
        return new NamedParameterJdbcTemplate(dataSource);
    }

    @Bean
    TransactionManager transactionManager(DataSource dataSource) {                     (5)
        return new DataSourceTransactionManager(dataSource);
    }
}
1 @EnableJdbcRepositories creates implementations for interfaces derived from Repository
2 AbstractJdbcConfiguration provides various default beans required by Spring Data JDBC
3 Creates a DataSource connecting to a database. This is required by the following two bean methods.
4 Creates the NamedParameterJdbcOperations used by Spring Data JDBC to access the database.
5 Spring Data JDBC utilizes the transaction management provided by Spring JDBC.

The configuration class in the preceding example sets up an embedded HSQL database by using the EmbeddedDatabaseBuilder API of spring-jdbc. The DataSource is then used to set up NamedParameterJdbcOperations and a TransactionManager. We finally activate Spring Data JDBC repositories by using the `@EnableJdbcRepositories. If no base package is configured, it uses the package in which the configuration class resides. Extending AbstractJdbcConfiguration ensures various beans get registered. Overwriting its methods can be used to customize the setup (see below).

This configuration can be further simplified by using Spring Boot. With Spring Boot a DataSource is sufficient once the starter spring-boot-starter-data-jdbc is included in the dependencies. Everything else is done by Spring Boot.

There are a couple of things one might want to customize in this setup.

Spring Data JDBC uses implementations of the interface Dialect to encapsulate behavior that is specific to a database or its JDBC driver. By default the AbstractJdbcConfiguration tries to determine the database in use an register the correct Dialect. This behavior can be changed by overwriting jdbcDialect(NamedParameterJdbcOperations).

Dialects are resolved by [JdbcDialectResolver] from JdbcOperations, typically by inspecting Connection. You can let Spring auto-discover your Dialect by registering a class that implements org.springframework.data.jdbc.repository.config.DialectResolver$JdbcDialectProvider through META-INF/spring.factories. DialectResolver discovers dialect provider implementations from the class path using Spring’s SpringFactoriesLoader.

2.4. Persisting Entities

Saving an aggregate can be performed with the CrudRepository.save(…) method. If the aggregate is new, this results in an insert for the aggregate root, followed by insert statements for all directly or indirectly referenced entities.

If the aggregate root is not new, all referenced entities get deleted, the aggregate root gets updated, and all referenced entities get inserted again. Note that whether an instance is new is part of the instance’s state.

This approach has some obvious downsides. If only few of the referenced entities have been actually changed, the deletion and insertion is wasteful. While this process could and probably will be improved, there are certain limitations to what Spring Data JDBC can offer. It does not know the previous state of an aggregate. So any update process always has to take whatever it finds in the database and make sure it converts it to whatever is the state of the entity passed to the save method.

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2.4.1. Supported Types in Your Entity

The properties of the following types are currently supported:

  • All primitive types and their boxed types (int, float, Integer, Float, and so on)

  • Enums get mapped to their name.

  • String

  • java.util.Date, java.time.LocalDate, java.time.LocalDateTime, and java.time.LocalTime

  • Arrays and Collections of the types mentioned above can be mapped to columns of array type if your database supports that.

  • Anything your database driver accepts.

  • References to other entities. They are considered a one-to-one relationship, or an embedded type. It is optional for one-to-one relationship entities to have an id attribute. The table of the referenced entity is expected to have an additional column named the same as the table of the referencing entity. You can change this name by implementing NamingStrategy.getReverseColumnName(PersistentPropertyPathExtension path). Embedded entities do not need an id. If one is present it gets ignored.

  • Set<some entity> is considered a one-to-many relationship. The table of the referenced entity is expected to have an additional column named the same as the table of the referencing entity. You can change this name by implementing NamingStrategy.getReverseColumnName(PersistentPropertyPathExtension path).

  • Map<simple type, some entity> is considered a qualified one-to-many relationship. The table of the referenced entity is expected to have two additional columns: One named the same as the table of the referencing entity for the foreign key and one with the same name and an additional _key suffix for the map key. You can change this behavior by implementing NamingStrategy.getReverseColumnName(PersistentPropertyPathExtension path) and NamingStrategy.getKeyColumn(RelationalPersistentProperty property), respectively. Alternatively you may annotate the attribute with @MappedCollection(idColumn="your_column_name", keyColumn="your_key_column_name")

  • List<some entity> is mapped as a Map<Integer, some entity>.

The handling of referenced entities is limited. This is based on the idea of aggregate roots as described above. If you reference another entity, that entity is, by definition, part of your aggregate. So, if you remove the reference, the previously referenced entity gets deleted. This also means references are 1-1 or 1-n, but not n-1 or n-m.

If you have n-1 or n-m references, you are, by definition, dealing with two separate aggregates. References between those should be encoded as simple id values, which should map properly with Spring Data JDBC.

2.4.2. Custom converters

Custom converters can be registered, for types that are not supported by default, by inheriting your configuration from AbstractJdbcConfiguration and overwriting the method jdbcCustomConversions().

@Configuration
public class DataJdbcConfiguration extends AbstractJdbcConfiguration {

    @Override
    public JdbcCustomConversions jdbcCustomConversions() {

      return new JdbcCustomConversions(Collections.singletonList(TimestampTzToDateConverter.INSTANCE));

    }

    @ReadingConverter
    enum TimestampTzToDateConverter implements Converter<TIMESTAMPTZ, Date> {

        INSTANCE;

        @Override
        public Date convert(TIMESTAMPTZ source) {
            //...
        }
    }
}

The constructor of JdbcCustomConversions accepts a list of org.springframework.core.convert.converter.Converter.

Converters should be annotated with @ReadingConverter or @WritingConverter in order to control their applicability to only reading from or to writing to the database.

TIMESTAMPTZ in the example is a database specific data type that needs conversion into something more suitable for a domain model.

JdbcValue

Value conversion uses JdbcValue to enrich values propagated to JDBC operations with a java.sql.Types type. Register a custom write converter if you need to specify a JDBC-specific type instead of using type derivation. This converter should convert the value to JdbcValue which has a field for the value and for the actual JDBCType.

2.4.3. NamingStrategy

When you use the standard implementations of CrudRepository that Spring Data JDBC provides, they expect a certain table structure. You can tweak that by providing a NamingStrategy in your application context.

2.4.4. Custom table names

When the NamingStrategy does not matching on your database table names, you can customize the names with the @Table annotation. The element value of this annotation provides the custom table name. The following example maps the MyEntity class to the CUSTOM_TABLE_NAME table in the database:

@Table("CUSTOM_TABLE_NAME")
public class MyEntity {
    @Id
    Integer id;

    String name;
}

2.4.5. Custom column names

When the NamingStrategy does not matching on your database column names, you can customize the names with the @Column annotation. The element value of this annotation provides the custom column name. The following example maps the name property of the MyEntity class to the CUSTOM_COLUMN_NAME column in the database:

public class MyEntity {
    @Id
    Integer id;

    @Column("CUSTOM_COLUMN_NAME")
    String name;
}

The @MappedCollection annotation can be used on a reference type (one-to-one relationship) or on Sets, Lists, and Maps (one-to-many relationship). idColumn element of the annotation provides a custom name for the foreign key column referencing the id column in the other table. In the following example the corresponding table for the MySubEntity class has a NAME column, and the CUSTOM_MY_ENTITY_ID_COLUMN_NAME column of the MyEntity id for relationship reasons:

public class MyEntity {
    @Id
    Integer id;

    @MappedCollection(idColumn = "CUSTOM_MY_ENTITY_ID_COLUMN_NAME")
    Set<MySubEntity> subEntities;
}

public class MySubEntity {
    String name;
}

When using List and Map you must have an additional column for the position of a dataset in the List or the key value of the entity in the Map. This additional column name may be customized with the keyColumn Element of the @MappedCollection annotation:

public class MyEntity {
    @Id
    Integer id;

    @MappedCollection(idColumn = "CUSTOM_COLUMN_NAME", keyColumn = "CUSTOM_KEY_COLUMN_NAME")
    List<MySubEntity> name;
}

public class MySubEntity {
    String name;
}

2.4.6. Embedded entities

Embedded entities are used to have value objects in your java data model, even if there is only one table in your database. In the following example you see, that MyEntity is mapped with the @Embedded annotation. The consequence of this is, that in the database a table my_entity with the two columns id and name (from the EmbeddedEntity class) is expected.

However, if the name column is actually null within the result set, the entire property embeddedEntity will be set to null according to the onEmpty of @Embedded, which nulls objects when all nested properties are null.
Opposite to this behavior USE_EMPTY tries to create a new instance using either a default constructor or one that accepts nullable parameter values from the result set.

Example 2. Sample Code of embedding objects
public class MyEntity {

    @Id
    Integer id;

    @Embedded(onEmpty = USE_NULL) (1)
    EmbeddedEntity embeddedEntity;
}

public class EmbeddedEntity {
    String name;
}
1 Nulls embeddedEntity if name in null. Use USE_EMPTY to instantiate embeddedEntity with a potential null value for the name property.

If you need a value object multiple times in an entity, this can be achieved with the optional prefix element of the @Embedded annotation. This element represents a prefix and is prepend for each column name in the embedded object.

Make use of the shortcuts @Embedded.Nullable & @Embedded.Empty for @Embedded(onEmpty = USE_NULL) and @Embedded(onEmpty = USE_EMPTY) to reduce verbosity and simultaneously set JSR-305 @javax.annotation.Nonnull accordingly.

public class MyEntity {

    @Id
    Integer id;

    @Embedded.Nullable (1)
    EmbeddedEntity embeddedEntity;
}
1 Shortcut for @Embedded(onEmpty = USE_NULL).

Embedded entities containing a Collection or a Map will always be considered non empty since they will at least contain the empty collection or map. Such an entity will therefore never be null even when using @Embedded(onEmpty = USE_NULL).

2.4.7. Entity State Detection Strategies

The following table describes the strategies that Spring Data JDBC offers for detecting whether an entity is new:

Table 1. Options for detection whether an entity is new in Spring Data JDBC

Id-Property inspection (the default)

By default, Spring Data JDBC inspects the identifier property of the given entity. If the identifier property is null, then the entity is assumed to be new. Otherwise, it is assumed to not be new.

Implementing Persistable

If an entity implements Persistable, Spring Data JDBC delegates the new detection to the isNew(…) method of the entity. See the Javadoc for details.

Implementing EntityInformation

You can customize the EntityInformation abstraction used in the SimpleJdbcRepository implementation by creating a subclass of JdbcRepositoryFactory and overriding the getEntityInformation(…) method. You then have to register the custom implementation of JdbcRepositoryFactory as a Spring bean. Note that this should rarely be necessary. See the Javadoc for details.

2.4.8. ID Generation

Spring Data JDBC uses the ID to identify entities. The ID of an entity must be annotated with Spring Data’s @Id annotation.

When your data base has an auto-increment column for the ID column, the generated value gets set in the entity after inserting it into the database.

One important constraint is that, after saving an entity, the entity must not be new any more. Note that whether an entity is new is part of the entity’s state. With auto-increment columns, this happens automatically, because the ID gets set by Spring Data with the value from the ID column. If you are not using auto-increment columns, you can use a BeforeSave listener, which sets the ID of the entity (covered later in this document).

2.4.9. Optimistic Locking

Spring Data JDBC supports optimistic locking by means of a numeric attribute that is annotated with @Version on the aggregate root. Whenever Spring Data JDBC saves an aggregate with such a version attribute two things happen: The update statement for the aggregate root will contain a where clause checking that the version stored in the database is actually unchanged. If this isn’t the case an OptimisticLockingFailureException will be thrown. Also the version attribute gets increased both in the entity and in the database so a concurrent action will notice the change and throw an OptimisticLockingFailureException if applicable as described above.

This process also applies to inserting new aggregates, where a null or 0 version indicates a new instance and the increased instance afterwards marks the instance as not new anymore, making this work rather nicely with cases where the id is generated during object construction for example when UUIDs are used.

During deletes the version check also applies but no version is increased.

2.5. Query Methods

This section offers some specific information about the implementation and use of Spring Data JDBC.

Most of the data access operations you usually trigger on a repository result in a query being run against the databases. Defining such a query is a matter of declaring a method on the repository interface, as the following example shows:

Example 3. PersonRepository with query methods
interface PersonRepository extends PagingAndSortingRepository<Person, String> {

  List<Person> findByFirstname(String firstname);                                   (1)

  List<Person> findByFirstnameOrderByLastname(String firstname, Pageable pageable); (2)

  Person findByFirstnameAndLastname(String firstname, String lastname);             (3)

  Person findFirstByLastname(String lastname);                                      (4)

  @Query("SELECT * FROM person WHERE lastname = :lastname")
  List<Person> findByLastname(String lastname);                                     (5)
}
1 The method shows a query for all people with the given lastname. The query is derived by parsing the method name for constraints that can be concatenated with And and Or. Thus, the method name results in a query expression of SELECT … FROM person WHERE firstname = :firstname.
2 Use Pageable to pass offset and sorting parameters to the database.
3 Find a single entity for the given criteria. It completes with IncorrectResultSizeDataAccessException on non-unique results.
4 In contrast to <3>, the first entity is always emitted even if the query yields more result documents.
5 The findByLastname method shows a query for all people with the given last name.

The following table shows the keywords that are supported for query methods:

Table 2. Supported keywords for query methods
Keyword Sample Logical result

After

findByBirthdateAfter(Date date)

birthdate > date

GreaterThan

findByAgeGreaterThan(int age)

age > age

GreaterThanEqual

findByAgeGreaterThanEqual(int age)

age >= age

Before

findByBirthdateBefore(Date date)

birthdate < date

LessThan

findByAgeLessThan(int age)

age < age

LessThanEqual

findByAgeLessThanEqual(int age)

age ⇐ age

Between

findByAgeBetween(int from, int to)

age BETWEEN from AND to

NotBetween

findByAgeBetween(int from, int to)

age NOT BETWEEN from AND to

In

findByAgeIn(Collection<Integer> ages)

age IN (age1, age2, ageN)

NotIn

findByAgeNotIn(Collection ages)

age NOT IN (age1, age2, ageN)

IsNotNull, NotNull

findByFirstnameNotNull()

firstname IS NOT NULL

IsNull, Null

findByFirstnameNull()

firstname IS NULL

Like, StartingWith, EndingWith

findByFirstnameLike(String name)

firstname LIKE name

NotLike, IsNotLike

findByFirstnameNotLike(String name)

firstname NOT LIKE name

Containing on String

findByFirstnameContaining(String name)

firstname LIKE '%' name +'%'

NotContaining on String

findByFirstnameNotContaining(String name)

firstname NOT LIKE '%' name +'%'

(No keyword)

findByFirstname(String name)

firstname = name

Not

findByFirstnameNot(String name)

firstname != name

IsTrue, True

findByActiveIsTrue()

active IS TRUE

IsFalse, False

findByActiveIsFalse()

active IS FALSE

Query derivation is limited to properties that can be used in a WHERE clause without using joins.

2.5.1. Query Lookup Strategies

The JDBC module supports defining a query manually as a String in a @Query annotation or as named query in a property file. Deriving a query from the name of the method is currently not supported.

2.5.2. Using @Query

The following example shows how to use @Query to declare a query method:

Example 4. Declare a query method by using @Query
public interface UserRepository extends CrudRepository<User, Long> {

  @Query("select firstName, lastName from User u where u.emailAddress = :email")
  User findByEmailAddress(@Param("email") String email);
}

For converting the query result into entities the same RowMapper is used by default as for the queries Spring Data JDBC generates itself. The query you provide must match the format the RowMapper expects. Columns for all properties that are used in the constructor of an entity must be provided. Columns for properties that get set via setter, wither or field access are optional. Properties that don’t have a matching column in the result will not be set. The query is used for populating the aggregate root, embedded entities and one-to-one relationships including arrays of primitive types which get stored and loaded as SQL-array-types. Separate queries are generated for maps, lists, sets and arrays of entities.

Spring fully supports Java 8’s parameter name discovery based on the -parameters compiler flag. By using this flag in your build as an alternative to debug information, you can omit the @Param annotation for named parameters.
Spring Data JDBC supports only named parameters.

2.5.3. Named Queries

If no query is given in an annotation as described in the previous section Spring Data JDBC will try to locate a named query. There are two ways how the name of the query can be determined. The default is to take the domain class of the query, i.e. the aggregate root of the repository, take its simple name and append the name of the method separated by a .. Alternatively the @Query annotation has a name attribute which can be used to specify the name of a query to be looked up.

Named queries are expected to be provided in the property file META-INF/jdbc-named-queries.properties on the classpath.

The location of that file may be changed by setting a value to @EnableJdbcRepositories.namedQueriesLocation.

Custom RowMapper

You can configure which RowMapper to use, either by using the @Query(rowMapperClass = …​.) or by registering a RowMapperMap bean and registering a RowMapper per method return type. The following example shows how to register DefaultQueryMappingConfiguration:

@Bean
QueryMappingConfiguration rowMappers() {
  return new DefaultQueryMappingConfiguration()
    .register(Person.class, new PersonRowMapper())
    .register(Address.class, new AddressRowMapper());
}

When determining which RowMapper to use for a method, the following steps are followed, based on the return type of the method:

  1. If the type is a simple type, no RowMapper is used.

    Instead, the query is expected to return a single row with a single column, and a conversion to the return type is applied to that value.

  2. The entity classes in the QueryMappingConfiguration are iterated until one is found that is a superclass or interface of the return type in question. The RowMapper registered for that class is used.

    Iterating happens in the order of registration, so make sure to register more general types after specific ones.

If applicable, wrapper types such as collections or Optional are unwrapped. Thus, a return type of Optional<Person> uses the Person type in the preceding process.

Using a custom RowMapper through QueryMappingConfiguration, @Query(rowMapperClass=…), or a custom ResultSetExtractor disables Entity Callbacks and Lifecycle Events as the result mapping can issue its own events/callbacks if needed.
Modifying Query

You can mark a query as being a modifying query by using the @Modifying on query method, as the following example shows:

@Modifying
@Query("UPDATE DUMMYENTITY SET name = :name WHERE id = :id")
boolean updateName(@Param("id") Long id, @Param("name") String name);

You can specify the following return types:

  • void

  • int (updated record count)

  • boolean(whether a record was updated)

2.6. MyBatis Integration

The execution of CRUD operations and query methods can be delegated to MyBatis. This section describes how to configure Spring Data JDBC to integrate with MyBatis and which conventions to follow to hand over the execution of the queries as well as the mapping to the library.

2.6.1. Configuration

The easiest way to properly plug MyBatis into Spring Data JDBC is by importing MyBatisJdbcConfiguration into you application configuration:

@Configuration
@EnableJdbcRepositories
@Import(MyBatisJdbcConfiguration.class)
class Application {

  @Bean
  SqlSessionFactoryBean sqlSessionFactoryBean() {
    // Configure MyBatis here
  }
}

As you can see, all you need to declare is a SqlSessionFactoryBean as MyBatisJdbcConfiguration relies on a SqlSession bean to be available in the ApplicationContext eventually.

2.6.2. Usage conventions

For each operation in CrudRepository, Spring Data JDBC runs multiple statements. If there is a SqlSessionFactory in the application context, Spring Data checks, for each step, whether the SessionFactory offers a statement. If one is found, that statement (including its configured mapping to an entity) is used.

The name of the statement is constructed by concatenating the fully qualified name of the entity type with Mapper. and a String determining the kind of statement. For example, if an instance of org.example.User is to be inserted, Spring Data JDBC looks for a statement named org.example.UserMapper.insert.

When the statement is run, an instance of [MyBatisContext] gets passed as an argument, which makes various arguments available to the statement.

The following table describes the available MyBatis statements:

Name Purpose CrudRepository methods that might trigger this statement Attributes available in the MyBatisContext

insert

Inserts a single entity. This also applies for entities referenced by the aggregate root.

save, saveAll.

getInstance: the instance to be saved

getDomainType: The type of the entity to be saved.

get(<key>): ID of the referencing entity, where <key> is the name of the back reference column provided by the NamingStrategy.

update

Updates a single entity. This also applies for entities referenced by the aggregate root.

save, saveAll.

getInstance: The instance to be saved

getDomainType: The type of the entity to be saved.

delete

Deletes a single entity.

delete, deleteById.

getId: The ID of the instance to be deleted

getDomainType: The type of the entity to be deleted.

deleteAll-<propertyPath>

Deletes all entities referenced by any aggregate root of the type used as prefix with the given property path. Note that the type used for prefixing the statement name is the name of the aggregate root, not the one of the entity to be deleted.

deleteAll.

getDomainType: The types of the entities to be deleted.

deleteAll

Deletes all aggregate roots of the type used as the prefix

deleteAll.

getDomainType: The type of the entities to be deleted.

delete-<propertyPath>

Deletes all entities referenced by an aggregate root with the given propertyPath

deleteById.

getId: The ID of the aggregate root for which referenced entities are to be deleted.

getDomainType: The type of the entities to be deleted.

findById

Selects an aggregate root by ID

findById.

getId: The ID of the entity to load.

getDomainType: The type of the entity to load.

findAll

Select all aggregate roots

findAll.

getDomainType: The type of the entity to load.

findAllById

Select a set of aggregate roots by ID values

findAllById.

getId: A list of ID values of the entities to load.

getDomainType: The type of the entity to load.

findAllByProperty-<propertyName>

Select a set of entities that is referenced by another entity. The type of the referencing entity is used for the prefix. The referenced entities type is used as the suffix. This method is deprecated. Use findAllByPath instead

All find* methods. If no query is defined for findAllByPath

getId: The ID of the entity referencing the entities to be loaded.

getDomainType: The type of the entity to load.

findAllByPath-<propertyPath>

Select a set of entities that is referenced by another entity via a property path.

All find* methods.

getIdentifier: The Identifier holding the id of the aggregate root plus the keys and list indexes of all path elements.

getDomainType: The type of the entity to load.

findAllSorted

Select all aggregate roots, sorted

findAll(Sort).

getSort: The sorting specification.

findAllPaged

Select a page of aggregate roots, optionally sorted

findAll(Page).

getPageable: The paging specification.

count

Count the number of aggregate root of the type used as prefix

count

getDomainType: The type of aggregate roots to count.

2.7. Lifecycle Events

Spring Data JDBC triggers events that get published to any matching ApplicationListener beans in the application context. For example, the following listener gets invoked before an aggregate gets saved:

@Bean
public ApplicationListener<BeforeSaveEvent<Object>> loggingSaves() {

	return event -> {

		Object entity = event.getEntity();
		LOG.info("{} is getting saved.";
	};
}

If you want to handle events only for a specific domain type you may derive your listener from AbstractRelationalEventListener and overwrite one or more of the onXXX methods, where XXX stands for an event type. Callback methods will only get invoked for events related to the domain type and their subtypes so you don’t require further casting.

public class PersonLoadListener extends AbstractRelationalEventListener<Person> {

	@Override
	protected void onAfterLoad(AfterLoadEvent<Person> personLoad) {
		LOG.info(personLoad.getEntity());
	}
}

The following table describes the available events:

Table 3. Available events
Event When It Is Published

BeforeDeleteEvent

Before an aggregate root gets deleted.

AfterDeleteEvent

After an aggregate root gets deleted.

BeforeConvertEvent

Before an aggregate root gets saved (that is, inserted or updated but after the decision about whether if it gets updated or deleted was made).

BeforeSaveEvent

Before an aggregate root gets saved (that is, inserted or updated but after the decision about whether if it gets updated or deleted was made).

AfterSaveEvent

After an aggregate root gets saved (that is, inserted or updated).

AfterLoadEvent

After an aggregate root gets created from a database ResultSet and all its property get set.

Lifecycle events depend on an ApplicationEventMulticaster, which in case of the SimpleApplicationEventMulticaster can be configured with a TaskExecutor, and therefore gives no guarantees when an Event is processed.

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2.7.1. Store-specific EntityCallbacks

Spring Data JDBC uses the EntityCallback API for its auditing support and reacts on the following callbacks:

Table 4. Available Callbacks
EntityCallback When It Is Published

BeforeDeleteCallback

Before an aggregate root gets deleted.

AfterDeleteCallback

After an aggregate root gets deleted.

BeforeConvertCallback

Before an aggregate root gets saved (that is, inserted or updated but after the decision about whether if it gets updated or deleted was made).

BeforeSaveCallback

Before an aggregate root gets saved (that is, inserted or updated but after the decision about whether if it gets updated or deleted was made).

AfterSaveCallback

After an aggregate root gets saved (that is, inserted or updated).

AfterLoadCallback

After an aggregate root gets created from a database ResultSet and all its property get set.

2.8. Custom Conversions

Spring Data JDBC allows registration of custom converters to influence how values are mapped in the database. Currently, converters are only applied on property-level.

2.8.1. Writing a Property by Using a Registered Spring Converter

The following example shows an implementation of a Converter that converts from a Boolean object to a String value:

import org.springframework.core.convert.converter.Converter;

@WritingConverter
public class BooleanToStringConverter implements Converter<Boolean, String> {

    @Override
    public String convert(Boolean source) {
        return source != null && source ? "T" : "F";
    }
}

There are a couple of things to notice here: Boolean and String are both simple types hence Spring Data requires a hint in which direction this converter should apply (reading or writing). By annotating this converter with @WritingConverter you instruct Spring Data to write every Boolean property as String in the database.

2.8.2. Reading by Using a Spring Converter

The following example shows an implementation of a Converter that converts from a String to a Boolean value:

@ReadingConverter
public class StringToBooleanConverter implements Converter<String, Boolean> {

    @Override
    public Boolean convert(String source) {
        return source != null && source.equalsIgnoreCase("T") ? Boolean.TRUE : Boolean.FALSE;
    }
}

There are a couple of things to notice here: String and Boolean are both simple types hence Spring Data requires a hint in which direction this converter should apply (reading or writing). By annotating this converter with @ReadingConverter you instruct Spring Data to convert every String value from the database that should be assigned to a Boolean property.

2.8.3. Registering Spring Converters with the JdbcConverter

class MyJdbcConfiguration extends AbstractJdbcConfiguration {

    // …

    @Overwrite
    @Bean
    public JdbcCustomConversions jdbcCustomConversions() {
        return new JdbcCustomConversions(Arrays.asList(new BooleanToStringConverter(), new StringToBooleanConverter()));
    }
}

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2.9. Logging

Spring Data JDBC does little to no logging on its own. Instead, the mechanics of JdbcTemplate to issue SQL statements provide logging. Thus, if you want to inspect what SQL statements are executed, activate logging for Spring’s NamedParameterJdbcTemplate or MyBatis.

2.10. Transactionality

CRUD methods on repository instances are transactional by default. For reading operations, the transaction configuration readOnly flag is set to true. All others are configured with a plain @Transactional annotation so that default transaction configuration applies. For details, see the Javadoc of SimpleJdbcRepository. If you need to tweak transaction configuration for one of the methods declared in a repository, redeclare the method in your repository interface, as follows:

Example 5. Custom transaction configuration for CRUD
public interface UserRepository extends CrudRepository<User, Long> {

  @Override
  @Transactional(timeout = 10)
  public List<User> findAll();

  // Further query method declarations
}

The preceding causes the findAll() method to be executed with a timeout of 10 seconds and without the readOnly flag.

Another way to alter transactional behavior is by using a facade or service implementation that typically covers more than one repository. Its purpose is to define transactional boundaries for non-CRUD operations. The following example shows how to create such a facade:

Example 6. Using a facade to define transactions for multiple repository calls
@Service
class UserManagementImpl implements UserManagement {

  private final UserRepository userRepository;
  private final RoleRepository roleRepository;

  @Autowired
  public UserManagementImpl(UserRepository userRepository,
    RoleRepository roleRepository) {
    this.userRepository = userRepository;
    this.roleRepository = roleRepository;
  }

  @Transactional
  public void addRoleToAllUsers(String roleName) {

    Role role = roleRepository.findByName(roleName);

    for (User user : userRepository.findAll()) {
      user.addRole(role);
      userRepository.save(user);
    }
}

The preceding example causes calls to addRoleToAllUsers(…) to run inside a transaction (participating in an existing one or creating a new one if none are already running). The transaction configuration for the repositories is neglected, as the outer transaction configuration determines the actual repository to be used. Note that you have to explicitly activate <tx:annotation-driven /> or use @EnableTransactionManagement to get annotation-based configuration for facades working. Note that the preceding example assumes you use component scanning.

2.10.1. Transactional Query Methods

To let your query methods be transactional, use @Transactional at the repository interface you define, as the following example shows:

Example 7. Using @Transactional at query methods
@Transactional(readOnly = true)
public interface UserRepository extends CrudRepository<User, Long> {

  List<User> findByLastname(String lastname);

  @Modifying
  @Transactional
  @Query("delete from User u where u.active = false")
  void deleteInactiveUsers();
}

Typically, you want the readOnly flag to be set to true, because most of the query methods only read data. In contrast to that, deleteInactiveUsers() uses the @Modifying annotation and overrides the transaction configuration. Thus, the method is with the readOnly flag set to false.

It is definitely reasonable to use transactions for read-only queries, and we can mark them as such by setting the readOnly flag. This does not, however, act as a check that you do not trigger a manipulating query (although some databases reject INSERT and UPDATE statements inside a read-only transaction). Instead, the readOnly flag is propagated as a hint to the underlying JDBC driver for performance optimizations.

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2.11. JDBC Auditing

In order to activate auditing, add @EnableJdbcAuditing to your configuration, as the following example shows:

Example 8. Activating auditing with Java configuration
@Configuration
@EnableJdbcAuditing
class Config {

  @Bean
  public AuditorAware<AuditableUser> auditorProvider() {
    return new AuditorAwareImpl();
  }
}

If you expose a bean of type AuditorAware to the ApplicationContext, the auditing infrastructure automatically picks it up and uses it to determine the current user to be set on domain types. If you have multiple implementations registered in the ApplicationContext, you can select the one to be used by explicitly setting the auditorAwareRef attribute of @EnableJdbcAuditing.

Appendix

Appendix A: Glossary

AOP

Aspect-Oriented Programming

CRUD

Create, Read, Update, Delete - Basic persistence operations

Dependency Injection

Pattern to hand a component’s dependency to the component from outside, freeing the component to lookup the dependent itself. For more information, see https://en.wikipedia.org/wiki/Dependency_Injection.

JPA

Java Persistence API

Spring

Java application framework — https://projects.spring.io/spring-framework

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