This guide walks you through the process of building an application the Apache Geode data management system.

What you’ll build

You will use Spring Data for Apache Geode to store and retrieve POJOs.

What you’ll need

How to complete this guide

Like most Spring Getting Started guides, you can start from scratch and complete each step or you can bypass basic setup steps that are already familiar to you. Either way, you end up with working code.

To start from scratch, move on to Starting with Spring Initializr.

To skip the basics, do the following:

When you finish, you can check your results against the code in gs-accessing-data-gemfire/complete.

Starting with Spring Initializr

For all Spring applications, you should start with the Spring Initializr. Spring Initializr offers a fast way to pull in all the dependencies you need for an application and does a lot of the set up for you. This example needs "Spring for Apache Geode" dependency.

The following listing shows an example pom.xml file when using Maven:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.1</version>
    </parent>

    <groupId>org.springframework</groupId>
    <artifactId>gs-accessing-data-gemfire</artifactId>
    <version>0.1.0</version>

    <properties>
        <spring-shell.version>1.2.0.RELEASE</spring-shell.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-geode</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.shell</groupId>
            <artifactId>spring-shell</artifactId>
            <version>${spring-shell.version}</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

The following listing shows an example build.gradle file when using Gradle:

plugins {
    id 'org.springframework.boot' version '2.4.1'
    id 'io.spring.dependency-management' version '1.0.8.RELEASE'
    id "io.freefair.lombok" version "5.3.0"
    id 'java'
}

apply plugin: 'eclipse'
apply plugin: 'idea'

group = "org.springframework"
version = "0.1.0"
sourceCompatibility = 1.8
targetCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    implementation "org.springframework.boot:spring-boot-starter"
    implementation "org.springframework.data:spring-data-geode"
    implementation "org.projectlombok:lombok"
    runtimeOnly "org.springframework.shell:spring-shell:1.2.0.RELEASE"
}

bootJar {
    baseName = 'gs-accessing-data-gemfire'
    version = '0.1.0'
}

Define a simple entity

Apache Geode is a In-Memory Data Grid (IMDG) that maps data to Regions. It is possible to configure distributed Regions that partition and replicate data across multiple nodes in a cluster. However, in this guide, you will be using a LOCAL Region so you don’t have to set up anything extra, such as an entire cluster of servers.

Apache Geode is a Key/Value store and a Region implements the java.util.concurrent.ConcurrentMap interface. Though you can treat a Region like a java.util.Map, it is quite a bit more sophisticated than just a simple Java Map given data is distributed, replicated and generally managed inside the Region.

In this example, you store Person objects in Apache Geode (a Region) using only a few annotations.

src/main/java/hello/Person.java

package hello;

import java.io.Serializable;

import org.springframework.data.annotation.Id;
import org.springframework.data.annotation.PersistenceConstructor;
import org.springframework.data.gemfire.mapping.annotation.Region;

import lombok.Getter;

@Region(value = "People")
public class Person implements Serializable {

  @Id
  @Getter
  private final String name;

  @Getter
  private final int age;

  @PersistenceConstructor
  public Person(String name, int age) {
    this.name = name;
    this.age = age;
  }

  @Override
  public String toString() {
    return String.format("%s is %d years old", getName(), getAge());
  }
}

Here you have a Person class with two fields, name and age. You also have a single, persistent constructor to populate the entities when creating a new instance. The class uses Project Lombok to simplify the implementation.

Notice that this class is annotated with @Region("People"). When Apache Geode stores an instance of this class, a new entry is created inside the "People" Region. This class also marks the name field with @Id. This signifies the identifier used to identify and track the Person data inside Apache Geode. Essentially, the @Id annotated field (e.g. name) is the key and the Person instance is the value in the key/value entry. There is no automated key generation in Apache Geode so you must set the id (i.e. name) prior to persisting the entity to Apache Geode.

The next important piece is the person’s age. Later in this guide, you will use it to fashion some queries.

The overridden toString() method will print out the person’s name and age.

Create simple queries

Spring Data for Apache Geode focuses on storing and accessing data in Apache Geode using Spring. It also inherits powerful functionality from the Spring Data Commons project, such as the ability to derive queries. Essentially, you don’t have to learn the query language of Apache Geode (OQL); you can simply write a handful of methods and the queries are written for you by the framework.

To see how this works, create an interface that queries Person objects stored in Apache Geode.

src/main/java/hello/PersonRepository.java

package hello;

import org.springframework.data.gemfire.repository.query.annotation.Trace;
import org.springframework.data.repository.CrudRepository;

public interface PersonRepository extends CrudRepository<Person, String> {

  @Trace
  Person findByName(String name);

  @Trace
  Iterable<Person> findByAgeGreaterThan(int age);

  @Trace
  Iterable<Person> findByAgeLessThan(int age);

  @Trace
  Iterable<Person> findByAgeGreaterThanAndAgeLessThan(int greaterThanAge, int lessThanAge);

}

PersonRepository extends the CrudRepository interface from Spring Data Commons and specifies types for the generic type parameters for both the value and the id (key) that the Repository works with, i.e. Person and String, respectively. Out-of-the-box, this interface comes with many operations, including basic CRUD (CREATE, READ UPDATE, DELETE) and simple query (e.g. findById(..)) data access operations.

You can define other queries as needed by simply declaring their method signature. In this case, you add findByName, which essentially searches for objects of type Person and finds one that matches on name.

You also have:

  • findByAgeGreaterThan to find people above a certain age

  • findByAgeLessThan to find people below a certain age

  • findByAgeGreaterThanAndAgeLessThan to find people in a certain age range

Let’s wire this up and see what it looks like!

Create an application class

Here you create an Application class with all the components.

src/main/java/hello/Application.java

package hello;

import static java.util.Arrays.asList;
import static java.util.stream.StreamSupport.stream;

import org.apache.geode.cache.client.ClientRegionShortcut;

import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.data.gemfire.config.annotation.ClientCacheApplication;
import org.springframework.data.gemfire.config.annotation.EnableEntityDefinedRegions;
import org.springframework.data.gemfire.repository.config.EnableGemfireRepositories;

@SpringBootApplication
@ClientCacheApplication(name = "AccessingDataGemFireApplication")
@EnableEntityDefinedRegions(
  basePackageClasses = Person.class,
  clientRegionShortcut = ClientRegionShortcut.LOCAL
)
@EnableGemfireRepositories
public class Application {

  public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
  }

  @Bean
  ApplicationRunner run(PersonRepository personRepository) {

    return args -> {

      Person alice = new Person("Adult Alice", 40);
      Person bob = new Person("Baby Bob", 1);
      Person carol = new Person("Teen Carol", 13);

      System.out.println("Before accessing data in Apache Geode...");

      asList(alice, bob, carol).forEach(person -> System.out.println("\t" + person));

      System.out.println("Saving Alice, Bob and Carol to Pivotal GemFire...");

      personRepository.save(alice);
      personRepository.save(bob);
      personRepository.save(carol);

      System.out.println("Lookup each person by name...");

      asList(alice.getName(), bob.getName(), carol.getName())
        .forEach(name -> System.out.println("\t" + personRepository.findByName(name)));

      System.out.println("Query adults (over 18):");

      stream(personRepository.findByAgeGreaterThan(18).spliterator(), false)
        .forEach(person -> System.out.println("\t" + person));

      System.out.println("Query babies (less than 5):");

      stream(personRepository.findByAgeLessThan(5).spliterator(), false)
        .forEach(person -> System.out.println("\t" + person));

      System.out.println("Query teens (between 12 and 20):");

      stream(personRepository.findByAgeGreaterThanAndAgeLessThan(12, 20).spliterator(), false)
        .forEach(person -> System.out.println("\t" + person));
    };
  }
}

In the configuration, you need to add the @EnableGemfireRepositories annotation.

  • By default, @EnableGemfireRepositories will scan the current package for any interfaces that extend one of Spring Data’s Repository interfaces. Use it’s basePackageClasses = MyRepository.class to safely tell Spring Data for Apache Geode to scan a different root package by type for application-specific Repository extensions.

A Apache Geode cache containing 1 or more Regions is required to store all the data. For that, you use 1 of Spring Data for Apache Geode’s convenient configuration-based annotations: @ClientCacheApplication, @PeerCacheApplication or `@CacheServerApplication.

Apache Geode supports different cache topologies like client/server, peer-to-peer (p2p) and even WAN arrangements. In p2p, a peer cache instance is embedded in the application and your application would have the ability to participate in a cluster as peer cache member. However, your application is subject to all the constraints of being a peer member in the cluster, so this is not as commonly used as, say, the client/server topology.

In our case, we will be using @ClientCacheApplication to create a "client" cache instance, which has the ability to connect to and communicate with a cluster of servers. However, to keep things simple, the client will just store data locally using a LOCAL, client Region, without the need to setup or run any servers.

Now, remember how you tagged Person to be stored in a Region called "People" using the SDG mapping annotation, @Region("People")? You define that Region here using the ClientRegionFactoryBean<String, Person> bean definition. You need to inject an instance of the cache you just defined while also naming it "People".

A Apache Geode cache instance (whether a peer or client) is just a container for Regions, which store your data. You can think of the cache as a schema in an RDBMS and Regions as the tables. However, a cache also performs other administrative functions to control and manage all your Regions.
The types are <String, Person>, matching the key type (String) with the value type (Person).

The public static void main method uses Spring Boot’s SpringApplication.run() to launch the application and invoke the ApplicationRunner (another bean definition) that performs the data access operations on Apache Geode using the application’s Spring Data Repository.

The application autowires an instance of PersonRepository that you just defined. Spring Data for Apache Geode will dynamically create a concrete class that implements this interface and plug in the needed query code to meet the interface’s obligations. This Repository instance is the used by the run() method to demonstrate the functionality.

Store and fetch data

In this guide, you are creating three local Person objects, Alice, Baby Bob, and Teen Carol. Initially, they only exist in memory. After creating them, you have to save them to Apache Geode.

Now you run several queries. The first looks up everyone by name. Then you execute a handful of queries to find adults, babies, and teens, all using the age attribute. With the logging turned up, you can see the queries Spring Data for Apache Geode writes on your behalf.

change the @ClientCacheApplication annotation logLevel attribute to "config" to see the Apache Geode OQL queries that are generated by SDG. Because the query methods (e.g. findByName) are annotated with SDG’s @Trace annotation, this turns on Apache Geode’s OQL query tracing (query-level logging), which shows you the generated OQL, execution time, whether any Apache Geode Indexes were used by the query to gather the results, and the number of rows returned by the query.

Build an executable JAR

You can run the application from the command line with Gradle or Maven. You can also build a single executable JAR file that contains all the necessary dependencies, classes, and resources and run that. Building an executable jar makes it easy to ship, version, and deploy the service as an application throughout the development lifecycle, across different environments, and so forth.

If you use Gradle, you can run the application by using ./gradlew bootRun. Alternatively, you can build the JAR file by using ./gradlew build and then run the JAR file, as follows:

java -jar build/libs/gs-accessing-data-gemfire-0.1.0.jar

If you use Maven, you can run the application by using ./mvnw spring-boot:run. Alternatively, you can build the JAR file with ./mvnw clean package and then run the JAR file, as follows:

java -jar target/gs-accessing-data-gemfire-0.1.0.jar
The steps described here create a runnable JAR. You can also build a classic WAR file.

You should see something like this (with other stuff like queries as well):

Before linking up with {apache-geode-name}...
	Alice is 40 years old.
	Baby Bob is 1 years old.
	Teen Carol is 13 years old.
Lookup each person by name...
	Alice is 40 years old.
	Baby Bob is 1 years old.
	Teen Carol is 13 years old.
Adults (over 18):
	Alice is 40 years old.
Babies (less than 5):
	Baby Bob is 1 years old.
Teens (between 12 and 20):
	Teen Carol is 13 years old.

Summary

Congratulations! You set up an Apache Geode cache client, stored simple entities, and developed quick queries.

See Also

The following guides may also be helpful:

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All guides are released with an ASLv2 license for the code, and an Attribution, NoDerivatives creative commons license for the writing.