java - Jackson xml and json root element

Question

I have a service which returns objects in JSON and XML format.

http://localhost:8091/apiN/xml/2

XML Result

<restObjectList>
    <restObjectList>
        <restObjectList>
            <timestamp>2017-06-19 17:01:01</timestamp>
            <title>Rest object</title>
            <fullText>This is the full text. ID: 1</fullText>
            <id>1</id>
            <value>0.1412789210135622</value>
        </restObjectList>
        <restObjectList>
            <timestamp>2017-06-19 17:01:01</timestamp>
            <title>Rest object</title>
            <fullText>This is the full text. ID: 2</fullText>
            <id>2</id>
            <value>0.9886539664938628</value>
        </restObjectList>
    </restObjectList>
</restObjectList>

http://localhost:8091/apiN/2

JSON result

{
    "restObjectList": [
        {
            "timestamp": "2017-06-19 17:01:01",
            "title": "Rest object",
            "fullText": "This is the full text. ID: 1",
            "id": 1,
            "value": 0.1412789210135622
        },
        {
            "timestamp": "2017-06-19 17:01:01",
            "title": "Rest object",
            "fullText": "This is the full text. ID: 2",
            "id": 2,
            "value": 0.9886539664938628
        }
    ]
}

Result I'd like to receive

xml

<restObjectList>
    <restObject>
        <timestamp>2017-06-19 17:01:01</timestamp>
        <title>Rest object</title>
        <fullText>This is the full text. ID: 1</fullText>
        <id>1</id>
        <value>0.1412789210135622</value>
    </restObject>
    <restObject>
        <timestamp>2017-06-19 17:01:01</timestamp>
        <title>Rest object</title>
        <fullText>This is the full text. ID: 2</fullText>
        <id>2</id>
        <value>0.9886539664938628</value>
    </restObject>
</restObjectList>

json

{
    "restObjectList": [{
        "restObject": {
            "timestamp": "2017-06-19 17:01:01",
            "title": "Rest object",
            "fullText": "This is the full text. ID: 1",
            "id": 1,
            "value": 0.1412789210135622
        }
    }, {
        "restObject": {
            "timestamp": "2017-06-19 17:01:01",
            "title": "Rest object",
            "fullText": "This is the full text. ID: 2",
            "id": 2,
            "value": 0.9886539664938628
        }
    }]
}

How do I wrap restObject for JSON and XML and fix XML data for restObjectList because this tag is repeated at different levels.

My code

RestObject

@JsonRootName(value = "restObject")
@XmlRootElement(name = "restObject")
public class RestObject implements Serializable {

    private LocalDateTime timestamp;
    private String title;
    private String fullText;
    private Long id;
    private Double value;

    //Getters, setters
}

RestObjectList

@JsonRootName(value = "restObjectList")
@XmlSeeAlso({RestObject.class})
public class RestObjectList {

    private List<RestObject> restObjectList;

    //Getter and setter
}

JacksonConfig

@Configuration
public class JacksonConfig {

    @Bean
    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(true).build();
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);//Use custom date-time format.
        objectMapper.configure(SerializationFeature.WRAP_ROOT_VALUE, false);
        objectMapper.configure(DeserializationFeature.UNWRAP_ROOT_VALUE, false);
        return objectMapper;
    }

    @Bean
    public ObjectMapper objectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.enable(SerializationFeature.WRAP_ROOT_VALUE);
        objectMapper.enable(DeserializationFeature.UNWRAP_ROOT_VALUE);
        return objectMapper;
    }
}

Answer 1

The JSON and XML structures are not equivalent. In XML you want a list of RestObject and in JSON you want a list whose elements wrap instances of RestObject in another object. This isn't something you can get with a simple Jackson annotation, you would need a custom serializer only for JSON serialization. First of all, getting the desired XML format is straightforward:

class RestObject implements Serializable {
    private LocalDateTime timestamp;
    private String title;
    private String fullText;
    private Long id;
    private Double value;
}

@JsonRootName("restObjectList")
class RestObjectList {
    @JacksonXmlProperty(localName = "restObject")
    @JacksonXmlElementWrapper(useWrapping = false)
    private List<RestObject> restObjectList;
}

If you absolutely want to wrap each element in the array in json you'll need a custom serializer e.g.

class RestObjectSerializer extends JsonSerializer<RestObject> {
    @Override
    public void serialize(RestObject value, JsonGenerator gen, SerializerProvider serializers) throws
            IOException {
        gen.writeStartObject();
        gen.writeObjectFieldStart("restObject");
        gen.writeObjectField("timeStamp", value.getTimestamp());
        gen.writeStringField("title", value.getTitle());
        // other fields
        gen.writeEndObject();
        gen.writeEndObject();
    }
}

And register only with the ObjectMapper that serializes JSON so it doesn't interfere with serialization to XML:

ObjectMapper mapper = new ObjectMapper();
SimpleModule module = new SimpleModule("MyModule");
module.addSerializer(RestObject.class, new RestObjectSerializer());
mapper.registerModule(module);