Spring Data REST is itself a Spring MVC application and is designed in such a way that it should integrate with your existing Spring MVC applications with very little effort. An existing (or future) layer of services can run alongside Spring Data REST with only minor considerations.

To install Spring Data REST alongside your application, simply add the required dependencies, include the stock @Configuration class RepositoryRestMvcConfiguration (or subclass it and perform any required manual configuration), and map some URLs to be managed by Spring Data REST.

The simplest way to get to started is if you are building a Spring Boot application. That’s because Spring Data REST has both a starter as well as auto-configuration.

To add Spring Data REST to a Gradle-based project, add the spring-data-rest-webmvc artifact to your compile-time dependencies:

To add Spring Data REST to a Maven-based project, add the spring-data-rest-webmvc artifact to your compile-time dependencies:

To install Spring Data REST alongside your existing Spring MVC application, you need to include the appropriate MVC configuration. Spring Data REST configuration is defined in a class called RepositoryRestMvcConfiguration. You can either import this class into your existing configuration using an @Import annotation or you can subclass it and override any of the configureXXX methods to add your own configuration to that of Spring Data REST.

In the following example, we’ll subclass the standard RepositoryRestMvcConfiguration and add some ResourceMapping configurations for the Person domain object to alter how the JSON will look and how the links to related entities will be handled.

Make sure you also configure Spring Data repositories for the store you use. For details on that, please consult the reference documentation for the corresponding Spring Data module.

At this point, you must also configure your key data store.

Spring Data REST officially supports:

These linked guides introduce how to add dependencies for the related data store, configure domain objects, and define repositories.

You can run your application as either a Spring Boot app (with links showns above) or configure it as a classic Spring MVC app.

From this point, you can are free to customize Spring Data REST with various options.

The core functionality of Spring Data REST is to export resources for Spring Data repositories. Thus, the core artifact to look at and potentially tweak to customize the way the exporting works is the repository interface. Assume the following repository interface:

For this repository, Spring Data REST exposes a collection resource at /orders. The path is derived from the uncapitalized, pluralized, simple class name of the domain class being managed. It also exposes an item resource for each of the items managed by the repository under the URI template /orders/{id}.

By default the HTTP methods to interact with these resources map to the according methods of CrudRepository. Read more on that in the sections on collection resources and item resources.

Spring Data REST exposes a collection resource named after the uncapitalized, pluralized version of the domain class the exported repository is handling. Both the name of the resource and the path can be customized using the @RepositoryRestResource on the repository interface.

Spring Data REST exposes a resource for individual collection items as sub-resources of the collection resource.

Spring Data REST exposes sub-resources of every item resource for each of the associations the item resource has. The name and path of the of the resource defaults to the name of the association property and can be customized using @RestResource on the association property.

The search resource returns links for all query methods exposed by a repository. The path and name of the query method resources can be modified using @RestResource on the method declaration.

The query method resource executes the query exposed through an individual query method on the repository interface.

Rather than return everything from a large result set, Spring Data REST recognizes some URL parameters that will influence the page size and starting page number.

If you extend PagingAndSortingRepository<T, ID> and access the list of all entities, you’ll get links to the first 20 entities. To set the page size to any other number, add a size parameter:

This will set the page size to 5.

To use paging in your own query methods, you need to change the method signature to accept an additional Pageable parameter and return a Page rather than a List. For example, the following query method will be exported to /people/search/nameStartsWith and will support paging:

The Spring Data REST exporter will recognize the returned Page and give you the results in the body of the response, just as it would with a non-paged response, but additional links will be added to the resource to represent the previous and next pages of data.

Spring Data REST recognizes sorting parameters that will use the Repository sorting support.

To have your results sorted on a particular property, add a sort URL parameter with the name of the property you want to sort the results on. You can control the direction of the sort by appending a , to the the property name plus either asc or desc. The following would use the findByNameStartsWith query method defined on the PersonRepository for all Person entities with names starting with the letter "K" and add sort data that orders the results on the name property in descending order:

To sort the results by more than one property, keep adding as many sort=PROPERTY parameters as you need. They will be added to the Pageable in the order they appear in the query string.

Spring Data REST returns a representation of a domain object that corresponds to the requested Accept type specified in the HTTP request.

Currently, only JSON representations are supported. Other representation types can be supported in the future by adding an appropriate converter and updating the controller methods with the appropriate content-type.

Sometimes the behavior of the Spring Data REST’s ObjectMapper, which has been specially configured to use intelligent serializers that can turn domain objects into links and back again, may not handle your domain model correctly. There are so many ways one can structure your data that you may find your own domain model isn’t being translated to JSON correctly. It’s also sometimes not practical in these cases to try and support a complex domain model in a generic way. Sometimes, depending on the complexity, it’s not even possible to offer a generic solution.

Look at the following domain model:

This Person has several attributes:

Now assume we create a corresponding repository as follows:

By default, Spring Data REST will export this domain object including all of its attributes. firstName and lastName will be exported as the plain data objects that they are. There are two options regarding the address attribute. One option is to also define a repository for Address objects like this:

In this situation, a Person resource will render the address attribute as a URI to it’s corresponding Address resource. If we were to look up "Frodo" in the system, we could expect to see a HAL document like this:

There is another route. If the Address domain object does not have it’s own repository definition, Spring Data REST will inline the data fields right inside the Person resource.

But what if you don’t want address details at all? Again, by default, Spring Data REST will export all its attributes (except the id). You can offer the consumer of your REST service an alternative by defining one or more projections.

This projection has the following details:

The NoAddresses projection only has getters for firstName and lastName meaning that it won’t serve up any address information. Assuming you have a separate repository for Address resources, the default view from Spring Data REST is slightly different as shown below:

To view apply the projection to the resource, look up http://localhost:8080/persons/1/projection=noAddresses.

It’s possible to have multiple projections.

An excerpt is a projection that is applied to a repository automatically. For an example, you can alter the PersonRepository as follows:

This directs Spring Data REST to use the NoAddresses projection when embedding Person resources into collections or related resources.

In addition to altering the default rendering, excerpts have additional rednering options as shown below.

A common situation with REST services arises when you compose domain objects. For example, a Person is stored in one table and their related Address is stored in another. By default, Spring Data REST will serve up the person’s address as a URI the client must navigate. But if it’s common for consumers to always fetch this extra piece of data, an excerpt projection can go ahead and inline this extra piece of data, saving you an extra GET. To do so, let’s define another excerpt projection:

We can plug it into the PersonRepository definition as follows:

This will cause the HAL document to appear as follows:

This should appear as a mix of what you’ve seen so far.

If you would rather not use the bean name prefix approach, then you simply need to register an instance of your validator with the bean whose job it is to invoke validators after the correct event. In your configuration that subclasses Spring Data REST’s RepositoryRestMvcConfiguration, override the configureValidatingRepositoryEventListener method and call the addValidator method on the ValidatingRepositoryEventListener, passing the event you want this validator to be triggered on, and an instance of the validator.

There is an abstract class you can subclass which listens for these kinds of events and calls the appropriate method based on the event type. You just override the methods for the events you’re interested in.

One thing to note with this approach, however, is that it makes no distinction based on the type of the entity. You’ll have to inspect that yourself.

Another approach is to use an annotated handler, which does filter events based on domain type.

To declare a handler, create a POJO and put the @RepositoryEventHandler annotation on it. This tells the BeanPostProcessor that this class needs to be inspected for handler methods.

Once it finds a bean with this annotation, it iterates over the exposed methods and looks for annotations that correspond to the event you’re interested in. For example, to handle `BeforeSaveEvent`s in an annotated POJO for different kinds of domain types, you’d define your class like this:

The domain type whose events you’re interested in is determined from the type of the first parameter of the annotated methods.

Just declare an instance of your annotated bean in your ApplicationContext and the BeanPostProcessor that is by default created in RepositoryRestMvcConfiguration will inspect the bean for handlers and wire them to the correct events.

Spring Data REST provides an ALPS document for every exported repository. It contains information about both the RESTful transitions as well as the attributes of each repository.

At the root of a Spring Data REST app is a profile link. Assuming you had an app with both persons and related address, the root document would look like this:

A profile link, as defined in RFC 6906, is a place to include application level details. The ALPS draft spec is meant to define a particular profile format which we’ll explore further down in this section.

If you navigate into the profile link at localhost:8080/alps, you would see something like this:

Let’s navigate to /alps/persons and look at the profile data for a Person resource.

Configuring the segments of the URL path under which the resources of a JPA repository are exported is simple. You just add an annotation at the class level and/or at the query method level.

By default, the exporter will expose your CrudRepository using the name of the domain class. Spring Data REST also applies the Evo Inflector to pluralize this word. So a repository defined as follows:

Will, by default, be exposed under the URL http://localhost:8080/persons/

To change how the repository is exported, add a @RestResource annotation at the class level:

Now the repository will be accessible under the URL: http://localhost:8080/people/

If you have query methods defined, those also default to be exposed by their name:

This would be exposed under the URL: http://localhost:8080/persons/search/findByName

To change the segment of the URL under which this query method is exposed, use the @RestResource annotation again:

Now this query method will be exposed under the URL: http://localhost:8080/people/search/names

If you have an existing Spring MVC application and you’d like to integrate Spring Data REST, it’s actually very easy.

Somewhere in your Spring MVC configuration (most likely where you configure your MVC resources) add a bean reference to the JavaConfig class that is responsible for configuring the RepositoryRestController. The class name is org.springframework.data.rest.webmvc.RepositoryRestMvcConfiguration.

In Java, this would look like:

In XML this would look like:

When your ApplicationContext comes across this bean definition it will bootstrap the necessary Spring MVC resources to fully-configure the controller for exporting the repositories it finds in that ApplicationContext and any parent contexts.

Sometimes in your application you need to provide links to other resources from a particular entity. For example, a Customer response might be enriched with links to a current shopping cart, or links to manage resources related to that entity. Spring Data REST provides integration with Spring HATEOAS and provides an extension hook for users to alter the representation of resources going out to the client.

Sometimes the behavior of the Spring Data REST’s ObjectMapper, which has been specially configured to use intelligent serializers that can turn domain objects into links and back again, may not handle your domain model correctly. There are so many ways one can structure your data that you may find your own domain model isn’t being translated to JSON correctly. It’s also sometimes not practical in these cases to try and support a complex domain model in a generic way. Sometimes, depending on the complexity, it’s not even possible to offer a generic solution.

So to accommodate the largest percentage of the use cases, Spring Data REST tries very hard to render your object graph correctly. It will try and serialize unmanaged beans as normal POJOs and it will try and create links to managed beans where that’s necessary. But if your domain model doesn’t easily lend itself to reading or writing plain JSON, you may want to configure Jackson’s ObjectMapper with your own custom type mappings and (de)serializers.