MyConfiguration.java

package com.hazelcast.samples.eureka.partition.groups;

import com.hazelcast.client.HazelcastClient;
import com.hazelcast.client.config.ClientConfig;
import com.hazelcast.core.HazelcastInstance;
import com.hazelcast.spi.discovery.integration.DiscoveryServiceProvider;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * Configuration that is sufficient for Spring Boot to create a
 * Hazelcast client.
 * <p>
 * Although it's all that is strictly needed, depending on the Spring Boot
 * version we might need to manually create the Hazelcast client using
 * the {@code ClientConfig} {@code @Bean}.
 */
@Configuration
public class MyConfiguration {

    /**
     * Create a Hazelcast configuration object for a client that differs from
     * the default in two ways.
     * <ol>
     * <li><b>Name</b>
     * Since the server has given the cluster a name to prevent accidental
     * connections, the cluster must use this name to be able to connect.
     * </li>
     * <li><b>Networking</b>
     * To find <em>some</em> servers to try to connect to, the client looks
     * up {@code Eureka} for their addresses. Actually, Eureka here returns
     * all the servers, but for the client we only need one to respond to
     * establish a connection.
     * </li>
     * Clients don't store date so don't care are about partition groups.
     * Though the can have a local "<em>near-cache</em>" copy for even greater
     * speed.
     *
     * @param discoveryServiceProvider A {@link MyDiscoveryServiceProvider} instance.
     * @return Configuration for a Hazelcast client.
     */
    @Bean
    public ClientConfig clientConfig(DiscoveryServiceProvider discoveryServiceProvider) {
        ClientConfig clientConfig = new ClientConfig();

        // Naming
        clientConfig.getGroupConfig().setName(Constants.CLUSTER_NAME);

        // Discovery
        clientConfig.setProperty("hazelcast.discovery.enabled", Boolean.TRUE.toString());
        clientConfig.getNetworkConfig().getDiscoveryConfig().setDiscoveryServiceProvider(discoveryServiceProvider);

        return clientConfig;
    }

    /**
     * Temporary coding (hopefully).
     * <p>
     * Spring Boot deduces if a Hazelcast {@link com.hazelcast.config.Config Config} is present
     * then a Hazelcast instance is required, but doesn't yet do this for a
     * {@link com.hazelcast.client.config.ClientConfig ClientConfig}.
     * <p>
     * So help Spring Boot along, if the coding hasn't yet created a {@code HazelcastInstance}
     * {@code @Bean}, do it for Spring Boot using the client configuration created above.
     */
    @Configuration
    @ConditionalOnMissingBean(HazelcastInstance.class)
    static class HazelcastClientConfiguration {

        /**
         * Create a Hazelcast instance, a client rather than
         * a server.
         *
         * @param clientConfig Config to use, client config for a client
         * @return The Hazelcast instance.
         */
        @Bean
        public HazelcastInstance hazelcastInstance(ClientConfig clientConfig) {
            return HazelcastClient.newHazelcastClient(clientConfig);
        }
    }
}