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.