Java

Learn how to connect to Redis databases in Sealos DevBox using Java

This guide will walk you through the process of connecting to a Redis database using Java within your Sealos DevBox project.

Prerequisites

Project Setup

Create a new Maven project

In your Sealos DevBox terminal, initialize a new Maven project:

mvn archetype:generate -DgroupId=com.example -DartifactId=redis-java-example -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
mv redis-java-example/* .
rm -rf redis-java-example/

Project Structure

After setting up, your project structure should look like this:

/
├── pom.xml
├── src
│   ├── main
│   │   ├── java
│   │   │   └── com
│   │   │       └── example
│   │   │           ├── App.java
│   │   │           ├── RedisConfig.java
│   │   │           └── RedisConnection.java
│   │   └── resources
│   │       └── redis.properties
│   └── test
│       └── java
│           └── com
│               └── example
│                   └── AppTest.java

Update pom.xml

Replace the content of your pom.xml file with the following:

pom.xml
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
 
    <groupId>com.example</groupId>
    <artifactId>redis-java-example</artifactId>
    <version>1.0-SNAPSHOT</version>
 
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
    </properties>
 
    <dependencies>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>4.3.1</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>2.0.5</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.4.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>11</source>
                    <target>11</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.4</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <mainClass>com.example.App</mainClass>
                                </transformer>
                            </transformers>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

This pom.xml file includes the necessary dependencies (Jedis for Redis connectivity, SLF4J for logging) and configures the Maven Shade plugin to create an executable JAR.

Create a configuration file

Create a file named redis.properties in the src/main/resources directory:

redis.properties
redis.host=your_redis_host
redis.port=6379
redis.password=your_redis_password

Replace the placeholders with your actual Redis credentials from the Database app in Sealos.

Create Java classes

Create the following Java classes in the src/main/java/com/example directory:

  1. App.java:

    App.java
    package com.example;
 
import redis.clients.jedis.Jedis;
 
public class App {
    public static void main(String[] args) {
        try (Jedis jedis = RedisConnection.getConnection()) {
            System.out.println("Connected to Redis");
 
            // String operations
            jedis.set("mykey", "Hello from Sealos DevBox!");
            String value = jedis.get("mykey");
            System.out.println("Retrieved value: " + value);
 
            // List operations
            jedis.lpush("mylist", "element1", "element2", "element3");
            String listElement = jedis.lpop("mylist");
            System.out.println("Popped element from list: " + listElement);
 
            // Hash operations
            jedis.hset("myhash", "field1", "value1");
            jedis.hset("myhash", "field2", "value2");
            String hashValue = jedis.hget("myhash", "field1");
            System.out.println("Retrieved hash value: " + hashValue);
 
        } catch (Exception e) {
            System.err.println("Error connecting to Redis: " + e.getMessage());
        } finally {
            RedisConnection.closePool();
        }
    }
}

    This is the main class that demonstrates basic Redis operations using Jedis:

    • It sets and gets a string value.
    • It pushes elements to a list and pops an element.
    • It sets and gets hash values.

  2. RedisConfig.java:

    RedisConfig.java
    package com.example;
 
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
 
public class RedisConfig {
    private static final Properties properties = new Properties();
 
    static {
        try (InputStream input = RedisConfig.class.getClassLoader().getResourceAsStream("redis.properties")) {
            if (input == null) {
                System.out.println("Sorry, unable to find redis.properties");
                System.exit(1);
            }
            properties.load(input);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
    public static String getHost() {
        return properties.getProperty("redis.host");
    }
 
    public static int getPort() {
        return Integer.parseInt(properties.getProperty("redis.port"));
    }
 
    public static String getPassword() {
        return properties.getProperty("redis.password");
    }
}

    This class loads the Redis connection details from the redis.properties file.

  3. RedisConnection.java:

    RedisConnection.java
    package com.example;
 
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;
 
public class RedisConnection {
    private static final JedisPool pool = new JedisPool(new JedisPoolConfig(),
            RedisConfig.getHost(),
            RedisConfig.getPort(),
            2000,
            RedisConfig.getPassword());
 
    public static Jedis getConnection() {
        return pool.getResource();
    }
 
    public static void closePool() {
        pool.close();
    }
}

    This class manages the Redis connection pool using Jedis.

  4. AppTest.java (in src/test/java/com/example):

    AppTest.java
    package com.example;
 
import static org.junit.Assert.assertTrue;
 
import org.junit.Test;
 
public class AppTest 
{
    @Test
    public void shouldAnswerWithTrue()
    {
        assertTrue( true );
    }
}

Build and Run

To build and run the project, use the following commands in your terminal:

mvn clean package
java -jar target/redis-java-example-1.0-SNAPSHOT.jar

If everything is set up correctly, you should see output demonstrating the Redis operations.

Best Practices

  1. Use a properties file to store Redis connection details.
  2. Implement a configuration class to load and provide access to Redis properties.
  3. Use a connection pool for better performance and resource management.
  4. Always close Redis connections after use (or use try-with-resources as shown in the example).
  5. Handle exceptions appropriately and provide meaningful error messages.
  6. Use Maven for dependency management and build automation.

Troubleshooting

If you encounter connection issues:

  1. Verify your Redis credentials in the redis.properties file.
  2. Ensure your Redis database is running and accessible from your DevBox environment.
  3. Check for any network restrictions in your DevBox environment.
  4. Confirm that the Jedis dependency is correctly specified in your pom.xml file.
  5. Make sure you're using the correct version of Java (11 in this example).

Conclusion

This guide provided a complete example of how to set up a Java project with Maven to connect to a Redis database in the Sealos DevBox environment. It includes all the necessary steps, from project creation to running the application, along with best practices and troubleshooting tips.

For more detailed information on using Redis with Java, refer to the Jedis GitHub repository.

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