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= Ignite for Java

This page explains system requirements for running Ignite, how to install Ignite, start a cluster and run a simple Hello World example.

== Prerequisites

Ignite was officially tested on:

include::includes/prereqs.adoc[]

If you use Java version 11 or later, see <<Running Ignite with Java 11 or later>> for details.

== Installing Ignite

include::includes/install-ignite.adoc[]


== Starting a Node

include::includes/starting-node.adoc[]

== Running Your First Application


Once the cluster is started, follow the steps below to run a simple HelloWorld example.

=== 1. Add Maven Dependency


The easiest way to get started with Ignite in Java is to use Maven dependency management.

Create a new Maven project with your favorite IDE and add the following dependencies in your project’s pom.xml file.

[source,xml,subs="attributes,specialchars"]
----
<properties>
    <ignite.version>{version}</ignite.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.apache.ignite</groupId>
        <artifactId>ignite-core</artifactId>
        <version>${ignite.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.ignite</groupId>
        <artifactId>ignite-spring</artifactId>
        <version>${ignite.version}</version>
    </dependency>
</dependencies>
----

=== 2. HelloWorld.java


Here is a sample HelloWord.java file that prints 'Hello World' and some other environment details on all
the server nodes of the cluster.
The sample shows how to prepare a cluster configuration with Java APIs, create a sample cache with some data in it, and execute custom Java logic on the server nodes.

[source,java]
----
public class HelloWorld {
    public static void main(String[] args) throws IgniteException {
        // Preparing IgniteConfiguration using Java APIs
        IgniteConfiguration cfg = new IgniteConfiguration();

        // The node will be started as a client node.
        cfg.setClientMode(true);

        // Classes of custom Java logic will be transferred over the wire from this app.
        cfg.setPeerClassLoadingEnabled(true);

        // Setting up an IP Finder to ensure the client can locate the servers.
        TcpDiscoveryMulticastIpFinder ipFinder = new TcpDiscoveryMulticastIpFinder();
        ipFinder.setAddresses(Collections.singletonList("127.0.0.1:47500..47509"));
        cfg.setDiscoverySpi(new TcpDiscoverySpi().setIpFinder(ipFinder));

        // Starting the node
        Ignite ignite = Ignition.start(cfg);

        // Create an IgniteCache and put some values in it.
        IgniteCache<Integer, String> cache = ignite.getOrCreateCache("myCache");
        cache.put(1, "Hello");
        cache.put(2, "World!");

        System.out.println(">> Created the cache and add the values.");

        // Executing custom Java compute task on server nodes.
        ignite.compute(ignite.cluster().forServers()).broadcast(new RemoteTask());

        System.out.println(">> Compute task is executed, check for output on the server nodes.");

        // Disconnect from the cluster.
        ignite.close();
    }

    /**
     * A compute tasks that prints out a node ID and some details about its OS and JRE.
     * Plus, the code shows how to access data stored in a cache from the compute task.
     */
    private static class RemoteTask implements IgniteRunnable {
        @IgniteInstanceResource
        Ignite ignite;

        @Override public void run() {
            System.out.println(">> Executing the compute task");

            System.out.println(
                "   Node ID: " + ignite.cluster().localNode().id() + "\n" +
                "   OS: " + System.getProperty("os.name") +
                "   JRE: " + System.getProperty("java.runtime.name"));

            IgniteCache<Integer, String> cache = ignite.cache("myCache");

            System.out.println(">> " + cache.get(1) + " " + cache.get(2));
        }
    }
}
----
[NOTE]
====
Don't forget to add imports for HelloWorld.java. It should be trivial as long as Maven solves all of the dependencies.

Plus, you might need to add these settings to your pom.xml if the IDE keeps using Java compiler from a version earlier than 1.8:
[source,xml]
----
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
</build>
----
====


=== 3. Run HelloWorld.java


Run HelloWorld.java. You will see 'Hello World!' and other environment details printed on all the server nodes.


== Further Examples

include::includes/exampleprojects.adoc[]

== Running Ignite with Java 11 or later

include::includes/java9.adoc[]