# Java Implementation
<a name="schema-registry-gs-serde-java"></a>

**Note**  
Prerequisites: Before completing the following steps, you will need to have a Amazon Managed Streaming for Apache Kafka (Amazon MSK) or Apache Kafka cluster running. Your producers and consumers need to be running on Java 8 or above.

To install the libraries on producers and consumers:

1. Inside both the producers’ and consumers’ pom.xml files, add this dependency via the code below:

   ```
   <dependency>
       <groupId>software.amazon.glue</groupId>
       <artifactId>schema-registry-serde</artifactId>
       <version>1.1.5</version>
   </dependency>
   ```

   Alternatively, you can clone the [AWS Glue Schema Registry Github repository](https://github.com/awslabs/aws-glue-schema-registry).

1. Setup your producers with these required properties:

   ```
   props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class.getName()); // Can replace StringSerializer.class.getName()) with any other key serializer that you may use
   props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, GlueSchemaRegistryKafkaSerializer.class.getName());
   props.put(AWSSchemaRegistryConstants.AWS_REGION, "us-east-2");
   properties.put(AWSSchemaRegistryConstants.DATA_FORMAT, "JSON"); // OR "AVRO"
   ```

   If there are no existing schemas, then auto-registration needs to be turned on (next step). If you do have a schema that you would like to apply, then replace "my-schema" with your schema name. Also the "registry-name" has to be provided if schema auto-registration is off. If the schema is created under the "default-registry" then registry name can be omitted.

1. (Optional) Set any of these optional producer properties. For detailed property descriptions, see [the ReadMe file](https://github.com/awslabs/aws-glue-schema-registry/blob/master/README.md).

   ```
   props.put(AWSSchemaRegistryConstants.SCHEMA_AUTO_REGISTRATION_SETTING, "true"); // If not passed, uses "false"
   props.put(AWSSchemaRegistryConstants.SCHEMA_NAME, "my-schema"); // If not passed, uses transport name (topic name in case of Kafka, or stream name in case of Kinesis Data Streams)
   props.put(AWSSchemaRegistryConstants.REGISTRY_NAME, "my-registry"); // If not passed, uses "default-registry"
   props.put(AWSSchemaRegistryConstants.CACHE_TIME_TO_LIVE_MILLIS, "86400000"); // If not passed, uses 86400000 (24 Hours)
   props.put(AWSSchemaRegistryConstants.CACHE_SIZE, "10"); // default value is 200
   props.put(AWSSchemaRegistryConstants.COMPATIBILITY_SETTING, Compatibility.FULL); // Pass a compatibility mode. If not passed, uses Compatibility.BACKWARD
   props.put(AWSSchemaRegistryConstants.DESCRIPTION, "This registry is used for several purposes."); // If not passed, constructs a description
   props.put(AWSSchemaRegistryConstants.COMPRESSION_TYPE, AWSSchemaRegistryConstants.COMPRESSION.ZLIB); // If not passed, records are sent uncompressed
   ```

   Auto-registration registers the schema version under the default registry ("default-registry"). If a `SCHEMA_NAME` is not specified in the previous step, then the topic name is inferred as `SCHEMA_NAME`. 

   See [Schema versioning and compatibility](schema-registry.md#schema-registry-compatibility) for more information on compatibility modes.

1. Setup your consumers with these required properties:

   ```
   props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
   props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, GlueSchemaRegistryKafkaDeserializer.class.getName());
   props.put(AWSSchemaRegistryConstants.AWS_REGION, "us-east-2"); // Pass an AWS Region
   props.put(AWSSchemaRegistryConstants.AVRO_RECORD_TYPE, AvroRecordType.GENERIC_RECORD.getName()); // Only required for AVRO data format
   ```

1. (Optional) Set these optional consumer properties. For detailed property descriptions, see [the ReadMe file](https://github.com/awslabs/aws-glue-schema-registry/blob/master/README.md).

   ```
   properties.put(AWSSchemaRegistryConstants.CACHE_TIME_TO_LIVE_MILLIS, "86400000"); // If not passed, uses 86400000
   props.put(AWSSchemaRegistryConstants.CACHE_SIZE, "10"); // default value is 200
   props.put(AWSSchemaRegistryConstants.SECONDARY_DESERIALIZER, "com.amazonaws.services.schemaregistry.deserializers.external.ThirdPartyDeserializer"); // For migration fall back scenario
   ```