Spring Cloud Function is a popular open-source framework used for creating serverless applications. It enables developers to create stateless functions that can be deployed on cloud platforms like AWS Lambda, Azure Functions, and Google Cloud Functions. AWS Lambda is a serverless compute service provided by Amazon Web Services that allows developers to run their code without provisioning or managing servers. In this article, we will discuss how to add custom Serializer and Deserializer to Jackson in Spring Cloud Function deployed on AWS Lambda.

Understanding Serializers and Deserializers

What are Serializers and Deserializers?

Serializers and Deserializers are components used for converting data from one format to another. In the context of Spring Cloud Function, serializers are used for converting Java objects into JSON, while deserializers are used for converting JSON into Java objects.

Why are they important in Spring Cloud Function and AWS?

Spring Cloud Function supports different message formats, including JSON, plain text, and byte arrays. AWS Lambda, on the other hand, supports only JSON as the input and output message format. This is where serializers and deserializers come into play. They enable the conversion of data between different formats, allowing developers to write functions that can be deployed on AWS Lambda.

Jackson Serialization and Deserialization

What is Jackson?

Jackson is a popular JSON parsing library for Java. It provides a set of annotations and APIs for converting Java objects to JSON and vice versa. Jackson is widely used in Spring applications, including Spring Cloud Function.

How does Jackson work?

Jackson provides two main classes for serialization and deserialization: ObjectMapper and JsonParser. ObjectMapper is used for converting Java objects to JSON, while JsonParser is used for converting JSON to Java objects. Jackson uses reflection to serialize and deserialize Java objects, making it easy for developers to work with complex object graphs.

Adding Custom Serializer and Deserializer to Jackson

Why do we need custom Serializer and Deserializer?

Jackson provides default serializers and deserializers for converting Java objects to JSON and vice versa. However, sometimes we need to customize the conversion process to meet specific requirements. For example, we may need to serialize or deserialize a custom data type or format. This is where custom serializers and deserializers come into play.

How to add custom Serializer and Deserializer to Jackson?

To add a custom serializer or deserializer to Jackson, we need to implement the Serializer or Deserializer interface provided by Jackson. The interface provides methods for serializing and deserializing Java objects. Once we have implemented the interface, we need to register the serializer or deserializer with the ObjectMapper.

public class CustomSerializer extends JsonSerializer<MyCustomType> {
    @Override
    public void serialize(MyCustomType value, JsonGenerator gen
        throws IOException, JsonProcessingException {
            gen.writeString(value.toString());
        }
    }
}

public class CustomDeserializer extends JsonDeserializer<MyCustomType> {
    @Override
    public MyCustomType deserialize(JsonParser p, DeserializationContext ctxt)
        throws IOException, JsonProcessingException {
            String str = p.getValueAsString();
            return new MyCustomType(str);
        }
    }
}

In the above code snippet, we have defined a custom serializer and deserializer for a custom data type MyCustomType. The serializer converts MyCustomType to a string, while the deserializer converts a string to MyCustomType. We can register these serializers and deserializers with the ObjectMapper as follows:

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule();
module.addSerializer(MyCustomType.class, new CustomSerializer());
module.addDeserializer(MyCustomType.class, new CustomDeserializer());
mapper.registerModule(module);

The above code registers the custom serializer and deserializer for the MyCustomType class with the ObjectMapper.

Implementation of Custom Serializer and Deserializer in AWS Lambda

What is AWS Lambda?

AWS Lambda is a compute service provided by Amazon Web Services that runs your code in response to events and automatically manages the compute resources for you. You can use AWS Lambda to run your code in response to various events, such as changes to data in an S3 bucket, updates to a DynamoDB table, or HTTP requests via API Gateway.

How to implement Custom Serializer and Deserializer in AWS Lambda?

To implement custom serializer and deserializer in AWS Lambda, we need to follow these steps:

1. Define the custom serializer and deserializer classes as shown in the previous section.
2. Create a Spring Cloud Function project that uses Jackson for serialization and deserialization.
3. Build a deployable package (JAR) of the project.
4. Create an AWS Lambda function using the AWS Management Console or AWS CLI.
5. Configure the function to use the deployable package.
6. Test the function with sample inputs.

Once the above steps are completed, the AWS Lambda function should be able to use the custom serializer and deserializer.

Best Practices for using Custom Serializer and Deserializer

When to use Custom Serializer and Deserializer?

Custom serializers and deserializers should be used when we need to customize the serialization or deserialization process to meet specific requirements. For example, if we need to serialize or deserialize a custom data type or format, we can use custom serializers and deserializers.

Common mistakes to avoid when using Custom Serializer and Deserializer

When using custom serializers and deserializers, we should keep the following best practices in mind:

1. Use a consistent naming convention for the serializer and deserializer classes.
2. Register the serializer and deserializer with the ObjectMapper only once.
3. Test the serializer and deserializer thoroughly with different input and output scenarios.