Using Predix Cache with Java

Get code samples and recommended libraries for using a Predix Cache service with Java.

Recommended Java Library

Jedis. See https://github.com/xetorthio/jedis

Alternative Java Libraries

Lettuce-io. See https://github.com/lettuce-io/lettuce-core
Lettuce.io and Redis-Sentinel. See https://github.com/lettuce-io/lettuce-core/wiki/Redis-Sentinel
Redisson. See https://github.com/redisson/redisson

Code Samples Using the Standalone Jedis Library

Add the following Jedis Maven dependency:

<dependency>
      <groupId>redis.clients</groupId>
      <artifactId>jedis</artifactId>
      <version>2.9.0</version>
      <type>jar</type>
      <scope>compile</scope>
  </dependency>

Configure the connection to your Redis service using the VCAP_SERVICES environment variable:

// Parse the redis config from the VCAP_SERVICES environment. Assumes there's only 
one Redis instance bound.
          String vcapServices = System.getenv("VCAP_SERVICES");
          JSONObject vcapJson = new JSONObject(vcapServices);
          JSONObject credentials =  vcapJson.getJSONArray("predix-cache") //
                                            .getJSONObject(0) //
                                            .getJSONObject("credentials");
          // Set up the Jedis pool
          JedisPoolConfig poolConfig = new JedisPoolConfig();
          JedisPool pool = new JedisPool(poolConfig,
                  credentials.getString("host"),
                  credentials.getInt("port"),
                  Protocol.DEFAULT_TIMEOUT,
                  credentials.getString("password"));

Test the connection:

// Get a jedis client resource from the pool to set and get key values
   Jedis jedis = pool.getResource();
   jedis.set("foo", "bar");
   String value = jedis.get("foo");

   // Close the Jedis connector when you're finished with it.
   jedis.close();

Using Spring Data Redis

The Spring web framework provides a suite of tools for automatically discovering and configuring connections to data services. Include the Spring Data Redis library in your Spring app's classpath to take advantage of these features.

Add the following Maven dependency:

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-redis</artifactId>
    <version>1.8.4.RELEASE</version>
</dependency>

To set up the Redis connection, inject a RedisTemplate Bean with the @Autowired decorator:
```
@Autowired
private RedisTemplate<String, String> redisTemplate;
```

Use the RedisTemplate to test the Redis connection:

// Use the ValueOperations class for simple string value key/value pairs in Redis
ValueOperations<String, String> valueOps = redisTemplate.opsForValue();
// Set and get the Redis keys
valueOps.set("foo", "bar");
String retrievedValue = valueOps.get("foo");

Jedis for High Availability Service Plans Using Sentinels

Configuring Jedis to use a Redis sentinel connection is similar to the above example for using a Standalone Jedis client. Include the same Maven dependency and parse the credentials from the environment in the same way. However, in this case you need to use a JedisSentinelPool instead of a JedisPool:

// Parse the Credentials from the environment
 String vcapServices = System.getenv("VCAP_SERVICES");
         JSONObject vcapJson = new JSONObject(vcapServices);
         JSONObject credentials = vcapJson.getJSONArray("predix-cache") //
                                          .getJSONObject(0) //
                                          .getJSONObject("credentials");

 // Create a set using the Redis hosts from the environment
 JSONArray redisNodes = credentials.getJSONArray("ip_list");
 int sentinelPort = credentials.getInt("sentinel_port");

 HashSet<String> sentinels = new HashSet<>();
 for (int i=0; i < redisNodes.length(); i++) {
     String sentinel = String.format("%s:%d", cacheNodes.getString(i), sentinelPort);
     sentinels.add(sentinel);
 }

 // Create the redisSentinelPool
 String masterName = credentials.getString("master_name");
 String password = credentials.getString("password");
 JedisSentinelPool pool = new JedisSentinelPool(masterName, sentinels, password);

Test the Predix Cache cluster connection:

Jedis jedis = sentinelPool.getResource();
  jedis.set("foo", "bar");
  String value = jedis.get("foo");

  // Close the Jedis connector when you're finished with it.
  jedis.close();