4. Repositories

4.1 Introduction

Implementing a data access layer of an application has been cumbersome for quite a while. Too much boilerplate code had to be written. Domain classes were anemic and not designed in a real object oriented or domain driven manner.

Using both of these technologies makes developers life a lot easier regarding rich domain model's persistence. Nevertheless the amount of boilerplate code to implement repositories especially is still quite high. So the goal of the repository abstraction of Spring Data is to reduce the effort to implement data access layers for various persistence stores significantly.

The following chapters will introduce the core concepts and interfaces of Spring Data repositories in general for detailled information on the specific features of a particular store consult the later chapters of this document.

[Note]Note

As this part of the documentation is pulled in from Spring Data Commons we have to decide for a particular module to be used as example. The configuration and code samples in this chapter are using the JPA module. Make sure you adapt e.g. the XML namespace declaration, types to be extended to the equivalents of the module you're actually using.

4.2 Core concepts

The central interface in Spring Data repository abstraction is Repository (probably not that much of a surprise). It is typeable to the domain class to manage as well as the id type of the domain class. This interface mainly acts as marker interface to capture the types to deal with and help us when discovering interfaces that extend this one. Beyond that there's CrudRepository which provides some sophisticated functionality around CRUD for the entity being managed.

Example 4.1. CrudRepository interface

public interface CrudRepository<T, ID extends Serializable>
    extends Repository<T, ID> {
                                                                                                                       (1)
    <S extends T> S save(S entity);
                                                                                                                       (2)
    T findOne(ID primaryKey);
                                                                                                                       (3)
    Iterable<T> findAll();

    Long count();
                                                                                                                       (4)
    void delete(T entity);
                                                                                                                       (5)
    boolean exists(ID primaryKey);
                                                                                                                       (6)
    // … more functionality omitted.
}

1

Saves the given entity.

2

Returns the entity identified by the given id.

3

Returns all entities.

4

Returns the number of entities.

5

Deletes the given entity.

6

Returns whether an entity with the given id exists.


Usually we will have persistence technology specific sub-interfaces to include additional technology specific methods. We will now ship implementations for a variety of Spring Data modules that implement this interface.

On top of the CrudRepository there is a PagingAndSortingRepository abstraction that adds additional methods to ease paginated access to entities:

Example 4.2. PagingAndSortingRepository

public interface PagingAndSortingRepository<T, ID extends Serializable> extends CrudRepository<T, ID> {

    Iterable<T> findAll(Sort sort);

    Page<T> findAll(Pageable pageable);
}

Accessing the second page of User by a page size of 20 you could simply do something like this:

PagingAndSortingRepository<User, Long> repository = // … get access to a bean
Page<User> users = repository.findAll(new PageRequest(1, 20));

4.3 Query methods

Next to standard CRUD functionality repositories are usually queries on the underlying datastore. With Spring Data declaring those queries becomes a four-step process:

  1. Declare an interface extending Repository or one of its sub-interfaces and type it to the domain class it shall handle.

    public interface PersonRepository extends Repository<User, Long> { … }
  2. Declare query methods on the interface.

    List<Person> findByLastname(String lastname);
  3. Setup Spring to create proxy instances for those interfaces.

    <?xml version="1.0" encoding="UTF-8"?>
    <beans:beans xmlns:beans="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns="http://www.springframework.org/schema/data/jpa"
      xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/data/jpa
        http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">
    
      <repositories base-package="com.acme.repositories" />
    
    </beans>
    [Note]Note

    Note that we use the JPA namespace here just by example. If you're using the repository abstraction for any other store you need to change this to the appropriate namespace declaration of your store module which should be exchanging jpa in favor of e.g. mongodb.

  4. Get the repository instance injected and use it.

    public class SomeClient {
    
      @Autowired
      private PersonRepository repository;
    
      public void doSomething() {
        List<Person> persons = repository.findByLastname("Matthews");
      }

At this stage we barely scratched the surface of what's possible with the repositories but the general approach should be clear. Let's go through each of these steps and figure out details and various options that you have at each stage.

4.3.1 Defining repository interfaces

As a very first step you define a domain class specific repository interface. It's got to extend Repository and be typed to the domain class and an ID type. If you want to expose CRUD methods for that domain type, extend CrudRepository instead of Repository.

Fine tuning repository definition

Usually you will have your repository interface extend Repository, CrudRepository or PagingAndSortingRepository. If you don't like extending Spring Data interfaces at all you can also annotate your repository interface with @RepositoryDefinition. Extending CrudRepository will expose a complete set of methods to manipulate your entities. If you would rather be selective about the methods being exposed, simply copy the ones you want to expose from CrudRepository into your domain repository.

Example 4.3. Selectively exposing CRUD methods

interface MyBaseRepository<T, ID extends Serializable> extends Repository<T, ID> {
  T findOne(ID id);
  T save(T entity);
}

interface UserRepository extends MyBaseRepository<User, Long> {

  User findByEmailAddress(EmailAddress emailAddress);
}

In the first step we define a common base interface for all our domain repositories and expose findOne(…) as well as save(…).These methods will be routed into the base repository implementation of the store of your choice because they are matching the method signatures in CrudRepository. So our UserRepository will now be able to save users, find single ones by id as well as triggering a query to find Users by their email address.

4.3.2 Defining query methods

Query lookup strategies

The next thing we have to discuss is the definition of query methods. There are two main ways that the repository proxy is able to come up with the store specific query from the method name. The first option is to derive the query from the method name directly, the second is using some kind of additionally created query. What detailed options are available pretty much depends on the actual store, however, there's got to be some algorithm that decides what actual query is created.

There are three strategies available for the repository infrastructure to resolve the query. The strategy to be used can be configured at the namespace through the query-lookup-strategy attribute. However, It might be the case that some of the strategies are not supported for specific datastores. Here are your options:

CREATE

This strategy will try to construct a store specific query from the query method's name. The general approach is to remove a given set of well-known prefixes from the method name and parse the rest of the method. Read more about query construction in the section called “Query creation”.

USE_DECLARED_QUERY

This strategy tries to find a declared query which will be used for execution first. The query could be defined by an annotation somewhere or declared by other means. Please consult the documentation of the specific store to find out what options are available for that store. If the repository infrastructure does not find a declared query for the method at bootstrap time it will fail.

CREATE_IF_NOT_FOUND (default)

This strategy is actually a combination of CREATE and USE_DECLARED_QUERY. It will try to lookup a declared query first but create a custom method name based query if no declared query was found. This is the default lookup strategy and thus will be used if you don't configure anything explicitly. It allows quick query definition by method names but also custom tuning of these queries by introducing declared queries as needed.

Query creation

The query builder mechanism built into Spring Data repository infrastructure is useful to build constraining queries over entities of the repository. We will strip the prefixes find…By, read…By, as well as get…By from the method and start parsing the rest of it. The introducing clause can contain further expressions such as a Distinct to set a distinct flag on the query to be created. However, the first By acts as delimiter to indicate the start of the actual criterias. At a very basic level you can define conditions on entity properties and concatenate them with AND and OR.

Example 4.4. Query creation from method names

public interface PersonRepository extends Repository<User, Long> {

  List<Person> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);

  // Enables the distinct flag for the query
  List<Person> findDistinctPeopleByLastnameOrFirstname(String lastname, String firstname);
  List<Person> findPeopleDistinctByLastnameOrFirstname(String lastname, String firstname);

  // Enabling ignoring case for an individual property
  List<Person> findByLastnameIgnoreCase(String lastname);
  // Enabling ignoring case for all suitable properties
  List<Person> findByLastnameAndFirstnameAllIgnoreCase(String lastname, String firstname);

  // Enabling static ORDER BY for a query
  List<Person> findByLastnameOrderByFirstnameAsc(String lastname);
  List<Person> findByLastnameOrderByFirstnameDesc(String lastname);
}

The actual result of parsing that method will of course depend on the persistence store we create the query for, however, there are some general things to notice. The expressions are usually property traversals combined with operators that can be concatenated. As you can see in the example you can combine property expressions with And and Or. Beyond that you also get support for various operators like Between, LessThan, GreaterThan, Like for the property expressions. As the operators supported can vary from datastore to datastore please consult the according part of the reference documentation.

As you can see the method parser also supports setting an ignore case flag for individual properties (e.g. findByLastnameIgnoreCase(…)) or for all properties of a type that support ignoring case (i.e. usually Strings, e.g. findByLastnameAndFirstnameAllIgnoreCase(…)). Whether ignoring cases is supported my differ from store to store, so consult the relevant sections of the store specific query method reference docs.

Static ordering can be applied by appending an OrderBy clause to the query method referencing a property and providing a sorting direction (Asc or Desc). To create a query method that supports dynamic sorting have a look at the section called “Special parameter handling”.

Property expressions

Property expressions can just refer to a direct property of the managed entity (as you just saw in the example above). On query creation time we already make sure that the parsed property is at a property of the managed domain class. However, you can also define constraints by traversing nested properties. Assume Persons have Addresses with ZipCodes. In that case a method name of

List<Person> findByAddressZipCode(ZipCode zipCode);

will create the property traversal x.address.zipCode. The resolution algorithm starts with interpreting the entire part (AddressZipCode) as property and checks the domain class for a property with that name (uncapitalized). If it succeeds it just uses that. If not it starts splitting up the source at the camel case parts from the right side into a head and a tail and tries to find the according property, e.g. AddressZip and Code. If we find a property with that head we take the tail and continue building the tree down from there. As in our case the first split does not match we move the split point to the left (Address, ZipCode).

Although this should work for most cases, there might be cases where the algorithm could select the wrong property. Suppose our Person class has an addressZip property as well. Then our algorithm would match in the first split round already and essentially choose the wrong property and finally fail (as the type of addressZip probably has no code property). To resolve this ambiguity you can use _ inside your method name to manually define traversal points. So our method name would end up like so:

List<Person> findByAddress_ZipCode(ZipCode zipCode);

Special parameter handling

To hand parameters to your query you simply define method parameters as already seen in the examples above. Besides that we will recognizes certain specific types to apply pagination and sorting to your queries dynamically.

Example 4.5. Using Pageable and Sort in query methods

Page<User> findByLastname(String lastname, Pageable pageable);

List<User> findByLastname(String lastname, Sort sort);

List<User> findByLastname(String lastname, Pageable pageable);

The first method allows you to pass a org.springframework.data.domain.Pageable instance to the query method to dynamically add paging to your statically defined query. Sorting options are handed via the Pageable instance too. If you only need sorting, simply add an org.springframework.data.domain.Sort parameter to your method. As you also can see, simply returning a List is possible as well. We will then not retrieve the additional metadata required to build the actual Page instance but rather simply restrict the query to lookup only the given range of entities.

[Note]Note

To find out how many pages you get for a query entirely we have to trigger an additional count query. This will be derived from the query you actually trigger by default.

4.3.3 Creating repository instances

So now the question is how to create instances and bean definitions for the repository interfaces defined.

XML Configuration

The easiest way to do so is by using the Spring namespace that is shipped with each Spring Data module that supports the repository mechanism. Each of those includes a repositories element that allows you to simply define a base package that Spring will scan for you.

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns:beans="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns="http://www.springframework.org/schema/data/jpa"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/data/jpa
    http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

  <repositories base-package="com.acme.repositories" />

</beans:beans>

In this case we instruct Spring to scan com.acme.repositories and all its sub packages for interfaces extending Repository or one of its sub-interfaces. For each interface found it will register the persistence technology specific FactoryBean to create the according proxies that handle invocations of the query methods. Each of these beans will be registered under a bean name that is derived from the interface name, so an interface of UserRepository would be registered under userRepository. The base-package attribute allows the use of wildcards, so that you can have a pattern of scanned packages.

Using filters

By default we will pick up every interface extending the persistence technology specific Repository sub-interface located underneath the configured base package and create a bean instance for it. However, you might want finer grained control over which interfaces bean instances get created for. To do this we support the use of <include-filter /> and <exclude-filter /> elements inside <repositories />. The semantics are exactly equivalent to the elements in Spring's context namespace. For details see Spring reference documentation on these elements.

E.g. to exclude certain interfaces from instantiation as repository, you could use the following configuration:

Example 4.6. Using exclude-filter element

<repositories base-package="com.acme.repositories">
  <context:exclude-filter type="regex" expression=".*SomeRepository" />
</repositories>

This would exclude all interfaces ending in SomeRepository from being instantiated.


JavaConfig

The repository infrastructure can also be triggered using a store-specific @Enable${store}Repositories annotation on a JavaConfig class. For an introduction into Java based configuration of the Spring container please have a look at the reference documentation.[1]

A sample configuration to enable Spring Data repositories would look something like this.

Example 4.7. Sample annotation based repository configuration

@Configuration
@EnableJpaRepositories("com.acme.repositories")
class ApplicationConfiguration {

  @Bean
  public EntityManagerFactory entityManagerFactory() {
    // …
  }
}

Note that the sample uses the JPA specific annotation which would have to be exchanged dependingon which store module you actually use. The same applies to the definition of the EntityManagerFactory bean. Please consult the sections covering the store-specific configuration.

Standalone usage

You can also use the repository infrastructure outside of a Spring container usage. You will still need to have some of the Spring libraries on your classpath but you can generally setup repositories programmatically as well. The Spring Data modules providing repository support ship a persistence technology specific RepositoryFactory that can be used as follows:

Example 4.8. Standalone usage of repository factory

RepositoryFactorySupport factory = … // Instantiate factory here
UserRepository repository = factory.getRepository(UserRepository.class);

4.4 Custom implementations

4.4.1 Adding behaviour to single repositories

Often it is necessary to provide a custom implementation for a few repository methods. Spring Data repositories easily allow you to provide custom repository code and integrate it with generic CRUD abstraction and query method functionality. To enrich a repository with custom functionality you have to define an interface and an implementation for that functionality first and let the repository interface you provided so far extend that custom interface.

Example 4.9. Interface for custom repository functionality

interface UserRepositoryCustom {

  public void someCustomMethod(User user);
}

Example 4.10. Implementation of custom repository functionality

class UserRepositoryImpl implements UserRepositoryCustom {

  public void someCustomMethod(User user) {
    // Your custom implementation
  }
}

Note that the implementation itself does not depend on Spring Data and can be a regular Spring bean. So you can use standard dependency injection behaviour to inject references to other beans, take part in aspects and so on.


Example 4.11. Changes to the your basic repository interface

public interface UserRepository extends CrudRepository<User, Long>, UserRepositoryCustom {

  // Declare query methods here
}

Let your standard repository interface extend the custom one. This makes CRUD and custom functionality available to clients.


Configuration

If you use namespace configuration the repository infrastructure tries to autodetect custom implementations by looking up classes in the package we found a repository using the naming conventions appending the namespace element's attribute repository-impl-postfix to the classname. This suffix defaults to Impl.

Example 4.12. Configuration example

<repositories base-package="com.acme.repository" />

<repositories base-package="com.acme.repository" repository-impl-postfix="FooBar" />

The first configuration example will try to lookup a class com.acme.repository.UserRepositoryImpl to act as custom repository implementation, where the second example will try to lookup com.acme.repository.UserRepositoryFooBar.

Manual wiring

The approach above works perfectly well if your custom implementation uses annotation based configuration and autowiring entirely as it will be treated as any other Spring bean. If your custom implementation bean needs some special wiring you simply declare the bean and name it after the conventions just described. We will then pick up the custom bean by name rather than creating an instance.

Example 4.13. Manual wiring of custom implementations (I)

<repositories base-package="com.acme.repository" />

<beans:bean id="userRepositoryImpl" class="…">
  <!-- further configuration -->
</beans:bean>

4.4.2 Adding custom behaviour to all repositories

In other cases you might want to add a single method to all of your repository interfaces. So the approach just shown is not feasible. The first step to achieve this is adding and intermediate interface to declare the shared behaviour

Example 4.14. An interface declaring custom shared behaviour

public interface MyRepository<T, ID extends Serializable>
  extends JpaRepository<T, ID> {

  void sharedCustomMethod(ID id);
}

Now your individual repository interfaces will extend this intermediate interface instead of the Repository interface to include the functionality declared. The second step is to create an implementation of this interface that extends the persistence technology specific repository base class which will then act as a custom base class for the repository proxies.

[Note]Note

The default behaviour of the Spring <repositories /> namespace is to provide an implementation for all interfaces that fall under the base-package. This means that if left in it's current state, an implementation instance of MyRepository will be created by Spring. This is of course not desired as it is just supposed to act as an intermediary between Repository and the actual repository interfaces you want to define for each entity. To exclude an interface extending Repository from being instantiated as a repository instance it can either be annotate it with @NoRepositoryBean or moved out side of the configured base-package.

Example 4.15. Custom repository base class

public class MyRepositoryImpl<T, ID extends Serializable>
  extends SimpleJpaRepository<T, ID> implements MyRepository<T, ID> {

  private EntityManager entityManager;

  // There are two constructors to choose from, either can be used.
  public MyRepositoryImpl(Class<T> domainClass, EntityManager entityManager) {
    super(domainClass, entityManager);

    // This is the recommended method for accessing inherited class dependencies.
    this.entityManager = entityManager;
  }

  public void sharedCustomMethod(ID id) {
    // implementation goes here
  }
}

The last step is to create a custom repository factory to replace the default RepositoryFactoryBean that will in turn produce a custom RepositoryFactory. The new repository factory will then provide your MyRepositoryImpl as the implementation of any interfaces that extend the Repository interface, replacing the SimpleJpaRepository implementation you just extended.

Example 4.16. Custom repository factory bean

public class MyRepositoryFactoryBean<R extends JpaRepository<T, I>, T, I extends Serializable>
  extends JpaRepositoryFactoryBean<R, T, I> {

  protected RepositoryFactorySupport createRepositoryFactory(EntityManager entityManager) {

    return new MyRepositoryFactory(entityManager);
  }

  private static class MyRepositoryFactory<T, I extends Serializable> extends JpaRepositoryFactory {

    private EntityManager entityManager;

    public MyRepositoryFactory(EntityManager entityManager) {
      super(entityManager);

      this.entityManager = entityManager;
    }

    protected Object getTargetRepository(RepositoryMetadata metadata) {

      return new MyRepositoryImpl<T, I>((Class<T>) metadata.getDomainClass(), entityManager);
    }

    protected Class<?> getRepositoryBaseClass(RepositoryMetadata metadata) {

      // The RepositoryMetadata can be safely ignored, it is used by the JpaRepositoryFactory
      //to check for QueryDslJpaRepository's which is out of scope.
      return MyRepository.class;
    }
  }
}

Finally you can either declare beans of the custom factory directly or use the factory-class attribute of the Spring namespace to tell the repository infrastructure to use your custom factory implementation.

Example 4.17. Using the custom factory with the namespace

<repositories base-package="com.acme.repository"
  factory-class="com.acme.MyRepositoryFactoryBean" />

4.5 Extensions

This chapter documents a set of Spring Data extensions that enable Spring Data usage in a variety of contexts. Currently most of the integration is targeted towards Spring MVC.

4.5.1 Domain class web binding for Spring MVC

Given you are developing a Spring MVC web applications you typically have to resolve domain class ids from URLs. By default it's your task to transform that request parameter or URL part into the domain class to hand it layers below then or execute business logic on the entities directly. This should look something like this:

@Controller
@RequestMapping("/users")
public class UserController {

  private final UserRepository userRepository;

  @Autowired
  public UserController(UserRepository userRepository) {
    Assert.notNull(repository, "Repository must not be null!");
    userRepository = userRepository;
  }

  @RequestMapping("/{id}")
  public String showUserForm(@PathVariable("id") Long id, Model model) {
    
    // Do null check for id
    User user = userRepository.findOne(id);
    // Do null check for user

    model.addAttribute("user", user);
    return "user";
  }
}

First you pretty much have to declare a repository dependency for each controller to lookup the entity managed by the controller or repository respectively. Beyond that looking up the entity is boilerplate as well as it's always a findOne(…) call. Fortunately Spring provides means to register custom converting components that allow conversion between a String value to an arbitrary type.

PropertyEditors

For versions up to Spring 3.0 simple Java PropertyEditors had to be used. Thus, we offer a DomainClassPropertyEditorRegistrar, that will look up all Spring Data repositories registered in the ApplicationContext and register a custom PropertyEditor for the managed domain class

<bean class="….web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
  <property name="webBindingInitializer">
    <bean class="….web.bind.support.ConfigurableWebBindingInitializer">
      <property name="propertyEditorRegistrars">
        <bean class="org.springframework.data.repository.support.DomainClassPropertyEditorRegistrar" />
      </property>
    </bean>
  </property>
</bean>

If you have configured Spring MVC like this you can turn your controller into the following that reduces a lot of the clutter and boilerplate.

@Controller
@RequestMapping("/users")
public class UserController {

  @RequestMapping("/{id}")
  public String showUserForm(@PathVariable("id") User user, Model model) {

    model.addAttribute("user", user);
    return "userForm";
  }
}

ConversionService

As of Spring 3.0 the PropertyEditor support is superseeded by a new conversion infrstructure that leaves all the drawbacks of PropertyEditors behind and uses a stateless X to Y conversion approach. We now ship with a DomainClassConverter that pretty much mimics the behaviour of DomainClassPropertyEditorRegistrar. To configure, simply declare a bean instance and pipe the ConversionService being used into it's constructor:

<mvc:annotation-driven conversion-service="conversionService" />

<bean class="org.springframework.data.repository.support.DomainClassConverter">
  <constructor-arg ref="conversionService" />
</bean>

If you're using JavaConfig you can simply extend WebMvcConfigurationSupport and hand the FormatingConversionService the configuration superclass provides into the DomainClassConverter instance you create.

class WebConfiguration extends WebMvcConfigurationSupport {

  // Other configuration omitted

  @Bean
  public DomainClassConverter<?> domainClassConverter() {
    return new DomainClassConverter<FormattingConversionService>(mvcConversionService());
  }
}

4.5.2 Web pagination

@Controller
@RequestMapping("/users")
public class UserController {

  // DI code omitted

  @RequestMapping
  public String showUsers(Model model, HttpServletRequest request) {

    int page = Integer.parseInt(request.getParameter("page"));
    int pageSize = Integer.parseInt(request.getParameter("pageSize"));

    Pageable pageable = new PageRequest(page, pageSize);

    model.addAttribute("users", userService.getUsers(pageable));
    return "users";
  }
}

As you can see the naive approach requires the method to contain an HttpServletRequest parameter that has to be parsed manually. We even omitted an appropriate failure handling which would make the code even more verbose. The bottom line is that the controller actually shouldn't have to handle the functionality of extracting pagination information from the request. So we include a PageableArgumentResolver that will do the work for you.

<bean class="….web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
  <property name="customArgumentResolvers">
    <list>
      <bean class="org.springframework.data.web.PageableArgumentResolver" />
    </list>
  </property>
</bean>

This configuration allows you to simplify controllers down to something like this:

@Controller
@RequestMapping("/users")
public class UserController {

  @RequestMapping
  public String showUsers(Model model, Pageable pageable) {

    model.addAttribute("users", userRepository.findAll(pageable));
    return "users";
  }
}

The PageableArgumentResolver will automatically resolve request parameters to build a PageRequest instance. By default it will expect the following structure for the request parameters:

Table 4.1. Request parameters evaluated by PageableArgumentResolver

pageThe page you want to retrieve
page.sizeThe size of the page you want to retrieve
page.sortThe property that should be sorted by
page.sort.dirThe direction that should be used for sorting

In case you need multiple Pageables to be resolved from the request (for multiple tables e.g.) you can use Spring's @Qualifier annotation to distinguish one from another. The request parameters then have to be prefixed with ${qualifier}_. So a method signature like this:

public String showUsers(Model model, 
      @Qualifier("foo") Pageable first,
      @Qualifier("bar") Pageable second) { … }

you'd have to populate foo_page and bar_page and the according subproperties.

Defaulting

The PageableArgumentResolver will use a PageRequest with the first page and a page size of 10 by default and will use that in case it can't resolve a PageRequest from the request (because of missing parameters e.g.). You can configure a global default on the bean declaration directly. In case you might need controller method specific defaults for the Pageable simply annotate the method parameter with @PageableDefaults and specify page (through pageNumber), page size (through value) as well as sort (the list of properties to sort by) as wel as sortDir (the direction to sort by) as annotation attributes:

public String showUsers(Model model, 
  @PageableDefaults(pageNumber = 0, value = 30) Pageable pageable) { … }

4.5.3 Repository populators

If you have been working with the JDBC module of Spring you're probably familiar with the support to populate a DataSource using SQL scripts. A similar abstraction is available on the repositories level although we don't use SQL as data definition language as we need to be store independent of course. Thus the populators support XML (through Spring's OXM abstraction) and JSON (through Jackson) to define data for the repositories to be populated with.

Assume you have a file data.json with the following content:

Example 4.18. Data defined in JSON

[ { "_class" : "com.acme.Person",
 "firstname" : "Dave",
  "lastname" : "Matthews" },
  { "_class" : "com.acme.Person",
 "firstname" : "Carter",
  "lastname" : "Beauford" } ]

You can easily populate you repositories by using the populator elements of the repository namespace provided in Spring Data Commons. To get the just shown data be populated to your PersonRepository all you need to do is the following:

Example 4.19. Declaring a Jackson repository populator

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:repository="http://www.springframework.org/schema/data/repository"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/data/repository
    http://www.springframework.org/schema/data/repository/spring-repository.xsd">

  <repository:jackson-populator location="classpath:data.json" />

</beans>

This declaration causes the data.json file being read, deserialized by a Jackson ObjectMapper. The type the JSON object will be unmarshalled to will be determined by inspecting the _class attribute of the JSON document. We will eventually select the appropriate repository being able to handle the object just deserialized.

To rather use XML to define the repositories shall be populated with you can use the unmarshaller-populator you hand one of the marshaller options Spring OXM provides you with.

Example 4.20. Declaring an unmarshalling repository populator (using JAXB)

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:repository="http://www.springframework.org/schema/data/repository"
  xmlns:oxm="http://www.springframework.org/schema/oxm"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/data/repository
    http://www.springframework.org/schema/data/repository/spring-repository.xsd
    http://www.springframework.org/schema/oxm
    http://www.springframework.org/schema/oxm/spring-oxm.xsd">

  <repository:unmarshaller-populator location="classpath:data.json" unmarshaller-ref="unmarshaller" />

  <oxm:jaxb2-marshaller contextPath="com.acme" />

</beans>