[BUG] Serialization of CloudEvent through Jackson does not include the serialized data object

[tomsnor]

Describe the bug
Due to the current implementation of CloudEvent, the data attribute of the CloudEvent is represented as org.example.functions.SerializableContent instead of the desired class.

To Reproduce
Steps to reproduce the behavior:

• Serialize a CloudEvent with Jackson

Code Snippet

package org.example.functions;

import com.azure.core.models.CloudEvent;
import com.azure.core.models.CloudEventDataFormat;
import com.azure.core.util.BinaryData;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Jackson {

    private static class Foo {
        private final String bar;

        public Foo(String bar) {
            this.bar = bar;
        }

        public String getBar() {
            return bar;
        }
    }

    public static void main(String[] args) throws Exception {
        ObjectMapper objectMapper = new ObjectMapper();
        BinaryData binaryData = BinaryData.fromObject(new Foo("bar"));
        CloudEvent cloudEvent = new CloudEvent("mySource", "myType", binaryData, CloudEventDataFormat.JSON, "application/json");
        System.out.println(objectMapper.writeValueAsString(cloudEvent));
    }
}

Expected behavior
The data object contains a correct representation:

{"id":"c4c53894-46ab-40ff-abe7-9fe2bc8c215e","source":"mySource","data":{"bar":"bar"},"data_base64":null,"type":"myType","time":null,"specversion":"1.0","dataschema":null,"datacontenttype":"application/json","subject":null}

instead of

{"id":"c4c53894-46ab-40ff-abe7-9fe2bc8c215e","source":"mySource","data":{"replayable":true,"length":13},"data_base64":null,"type":"myType","time":null,"specversion":"1.0","dataschema":null,"datacontenttype":"application/json","subject":null}

Setup (please complete the following information):

• OS: MacOs
• IDE: IntelliJ
• Library/Libraries: com.azure:azure-core:1.41.0
• Java version: 8
• App Server/Environment: N.A.
• Frameworks: N.A

Additional context

• Related issue in function worker: OutputBinding not compatible with com.azure.core.models.CloudEvent azure-functions-java-worker#720
• There is a @JsonIgnore annotation on com.azure.core.models.CloudEvent#binaryData
• There is a @JsonProperty annotation on com.azure.core.models.CloudEvent#data
• The getData implementation returns BinaryData instead of JsonNode
• Jackson serializes the data attribute through the getter method (getData) resulting in a mismatch and a loss of content.

  @JsonProperty("data")
    private JsonNode data;
    @JsonProperty("data_base64")
    private String dataBase64;
    @JsonIgnore
    private BinaryData binaryData;

    public BinaryData getData() {
        if (this.binaryData == null) {
            if (this.data != null) {
                this.binaryData = BinaryData.fromObject(this.data, SERIALIZER);
            } else if (this.dataBase64 != null) {
                this.binaryData = BinaryData.fromBytes(Base64.getDecoder().decode(this.dataBase64));
            }
        }

        return this.binaryData;
    }

Information Checklist
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• Bug Description Added
• Repro Steps Added
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[joshfree]

Expected: "data":{"bar":"bar"}
Actual: "data":{"replayable":true,"length":13}

Thank you for the detailed issue report, @tomsnor. @billwert could you please follow up?

[tomsnor]

@joshfree if possible, I'd like to make a PR myself. Let me know!

[alzimmermsft]

Hi @tomsnor, we gladly accept any contributions to the repository, so please feel free to submit a PR if you wish.

I'll add some context on what is likely happening here.

BinaryData is mostly just a wrapper around different implementations of BinaryDataContent that handle different data formats. These contents are bucketed into a few broad categories of BINARY, OBJECT, and TEXT which are then used by an internal Jackson Modules that determine how to handle serialization and deserialization of BinaryData. It looks like this is where the issue is coming from in your example as you're using an ObjectMapper external to the Azure SDKs, which we should work on having this scenario being handled correctly.

My thoughts on the design for this, BinaryData is just an object wrapper around the true handling managed by BinaryDataContent, so the BinaryDataContent property in BinaryData should be annotated with JsonValue. Then, BinaryDataContent should be annotated with JsonSerializer and JsonDeserializaer to handle serialization and deserialization without having to rely on JacksonAdapter. You can look to JsonPatchDocument and JsonPatchOperation for some guidance as this is roughly equivalent in functionality.

[tomsnor]

@alzimmermsft what do you think about annotating com.azure.core.util.BinaryData#content and com.azure.core.implementation.util.SerializableContent#content with @jsonvalue? As no 'special' serialization is needed for a POJO, I think the double @jsonvalue annotation should sufficient.

Would you expect a double check of all com.azure.core.implementation.util.BinaryDataContent subclasses in this PR?

[alzimmermsft]

@alzimmermsft what do you think about annotating com.azure.core.util.BinaryData#content and com.azure.core.implementation.util.SerializableContent#content with @jsonvalue? As no 'special' serialization is needed for a POJO, I think the double @jsonvalue annotation should sufficient.

Would you expect a double check of all com.azure.core.implementation.util.BinaryDataContent subclasses in this PR?

@tomsnor, I don't see any issues with that :)