An Example Spring Boot App
The versioned example Spring Boot Data GemFire app at
PCC-Sample-App-PizzaStore
uses the VMware Tanzu GemFire for VMs service instance as a system of record.
Directions for running the app are in the GitHub repository’s README.md
file.
The app is versioned, and branches of the repository represent Tanzu GemFire
versions.
For Tanzu GemFire v1.13, use the branch named
demo
.
The app uses Spring Boot Data GemFire. The documentation for this opinionated extension of Spring Data GemFire is at Spring Boot for Apache Geode & Pivotal GemFire Reference Guide.
The app saves pizza orders within the Apache Geode servers of a Tanzu GemFire service instance. A REST interface provides a way for the app to take orders for pizza toppings and sauces.
In addition, the app demonstrates:
- How to set up and run the app based on The App’s Location.
- Apache Geode continuous queries as used by a Spring Boot app.
Top Down Explanation
In this opinionated version of Spring Boot Data GemFire,
at the topmost level of the app,
the @SpringBootApplication
annotation causes
the app to have a ClientCache
instance.
Within the example app’s CloudcachePizzaStoreApplication
class,
place the annotation at the class definition level:
@SpringBootApplication
public class CloudcachePizzaStoreApplication
This app is the client within a standard client/server architecture. The Tanzu GemFire service instance contains the servers. The client cache is a driver for interactions with the servers.
The Spring repository construct is the preferred choice to use
for the data storage, which will be an Apache Geode region.
To implement it,
annotate this example’s PizzaRepository
implementation
with @Repository
:
@Repository
public interface PizzaRepository extends CrudRepository<Pizza, String>
An Apache Geode region underlies the Spring repository,
storing the ordered pizzas.
Annotate the Pizza
class model with @Region
:
@Region("Pizza")
public class Pizza {
Within the Pizza
class, identify the key of the Apache Geode region entries with
the @Id
annotation.
It is the name
field in this example:
@Getter @Id @NonNull
private final String name;
The @SpringBootApplication
annotation
results in a chain of opinionated defaults,
all of which are appropriate for this app.
It identifies the app as a client.
The client receives an Apache Geode client cache.
Any regions will default to type PROXY
.
A proxy type of region forwards all region operations to the
Gemfire servers; no data is stored within the app’s client cache.
See Configuring Regions for Spring details. See Region Design for Tanzu GemFire details on regions.
The App Contoller
The AppController
class implements the REST interface,
by annotating the class with @RestController
:
@RestController
public class AppController
As pizzas are ordered,
a CrudRepository.save()
operation causes a
Apache Geode put
operation that updates the region on the Apache Geode server.
Continuous Queries in the App
The app defines two continuous queries (CQ). See Handling Events for a brief introduction to continuous queries.
The first CQ queries for any (and every) pizza order. Its callback logs the order.
The second CQ queries for pizzas with a PESTO
sauce.
When a pesto-sauced pizza is ordered,
the callback adds that pizza to a second region called Name
.
Within a Spring Boot Data GemFire app, to specify a continuous query:
annotate the class that defines the queries with
@Component
:@Component public class PizzaQueries
annotate the callback method with
@ContinuousQuery
and define the query, as in the app’s pesto pizza order example:@ContinuousQuery(name = "PestoPizzaOrdersQuery", durable = true, query = "SELECT * FROM /Pizza p WHERE p.sauce.name = 'PESTO'") public void handlePestoPizzaOrder(CqEvent event)
The annotation causes an implementation of all three needed items for this type of event handling. It defines the query, registers the query as a continuous query event, and it identifies the callback method to invoke when the event occurs.