How to Connect to Redis in Java using Jedis

Introduction#

There are more than ten different client libraries to use with Redis in Java. One of the most popular clients is Jedis.

Remarks#

Further information:

• Java Redis Clients
• Jedis Github Repository
• Jedis Documentation/Wiki

Getting Jedis

The Jedis library is generally added to Java project using a dependency management system built into the build environment of the project. Two popular Java build systems are Maven and Gradle.

Using Gradle

To add the Jedis library to a Gradle project, you will need configure a repository and add a dependency. The following snippet shows how to add version 2.9.0 of the Jedis library to a Gradle project.

repositories {
    mavenCentral()
}

dependencies {
    compile 'redis.clients:jedis:2.9.0'
}

Using Maven

To add Jedis to a Maven project, you need to add a dependency to your dependency list and provide the coordinates of the library. The following snippet would be added to your pom.xml file:

<dependencies>
    <dependency>
        <groupId>redis.clients</groupId>
        <artifactId>jedis</artifactId>
        <version>2.9.0</version>
    </dependency>
</dependencies>

Connecting to Redis

Using a Pool

Most code will want to connect to Redis using a pool of shared connection objects. Connecting to Redis using a pool involves two different code block. At initialization time, your application needs to create the connection pool:

    JedisPoolConfig poolCfg = new JedisPoolConfig();
    poolCfg.setMaxTotal(3);

    pool = new JedisPool(poolCfg, hostname, port, 500, password, false);

The JedisPoolConfig provides options for tuning the pool.

As your application processes it’s workload, you will need to get a connection from the shared pool using the following code:

    try (Jedis jedis = pool.getResource()) {

        ...
    }

Best practice is to get the Jedis connection object from the pool within a try-with-resources block.

Without Pools

In some cases, such as a simple application or an integration test, you may not want to deal with shared pools and instead create the Jedis connection object directly. That can be accomplished with the following code:

try (Jedis jedis = new Jedis(hostname, port)) {
    jedis.connect();
    jedis.auth(password);
    jedis.select(db);

    . . .
}

Again, best practice is to create the Jedis client object within a try-with-resources block.

Executing Basic Get/Set Commands

Once you have established a connection to Redis you can get and set values using the Jedis connection object:

Get

String value = jedis.get(myKey);

Set

jedis.put(myKey, "some value");

Executing Commands

To execute a Redis command using Jedis, you make method calls against the Jedis object you created from the pool. Jedis exposes Redis commands as method calls, some example are:

- String get(String key) 
- Long geoadd(String key, double longitude, double latitude, String member)
- List<String> hmget(String key, String... fields)
- Long hsetnx(String key, String field, String value)

If you wanted to set the value of a String key in Redis you would use a code block similar to:

try (Jedis jedis = pool.getResource()) {

   String myKey = "users:20";
   String myValue = "active";

   jedis.set(myKey, myValue);
}