Convert Java Object to JsonNode in Jackson

java

json-serialization

objectmapper

jsonnode

byAnton Shumikhin·Oct 28, 2024

Use the power of Jackson's ObjectMapper and leverage its valueToTree() method for transforming any Java object into a JsonNode:

ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNode = mapper.valueToTree(new MyObject());

This command magically morphs your Java object, MyObject, into a JsonNode; ready for whatever JSON wizardry you plan.

For a versatile encore, try out mapper.convertValue(object, JsonNode.class):

ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNode = mapper.convertValue(new MyObject(), JsonNode.class);

The above approach ensures a direct and efficient conversion, like instant teleportation, skirting any stopovers at Stringville.

Efficient conversion strategies

Beware of nulls and defaults

ObjectMapper has an interesting relationship with null values. By default, null fields are invited to the JsonNode party. If you prefer them to stay away, just tell the mapper:

mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

One could say it's good to be null-inclusive, but hey, sometimes you just want to keep things clean.

Singling out custom types

Got an object that prides itself on being custom made or enjoy using polymorphism? No worries, ObjectMapper can handle that too, just remember to introduce your special module first:

mapper.registerModule(new MyCustomModule());

Here, mapper = bouncer; MyCustomModule = VIP pass.

Performance? Yes, please!

If your object resembles a metropolitan city map, consider the performance costs of conversion. Direct methods like valueToTree() and convertValue() are your fast travel options.

Beyond conversion: using JsonNode

Navigating the JSON tree

JsonNode is a powerful robust tree traversing guide. Watch it lead the way with methods like get, path, and findValue:

JsonNode childNode = jsonNode.get("childFieldName"); // "Follow me, please"
JsonNode missingNode = jsonNode.path("fieldNameThatMayNotExist"); // "Hmm, nope. No path here."
List<JsonNode> foundValues = jsonNode.findValues("commonFieldNameAcrossTree"); // "Found 'em all! Pokemon style."

Modifying your JsonNode

Change is inevitable, and JsonNode knows that. Use methods like put and remove to keep your JSON up-to-date:

((ObjectNode) jsonNode).put("newFieldName", "newValue"); // New kid on the block
((ObjectNode) jsonNode).remove("obsoleteFieldName"); // Thanos snapped!

Reverse process: JsonNode to Java Object

Want to return to your origins? When needed, use the treeToValue method to get back to your Java Object:

MyObject myObject = mapper.treeToValue(jsonNode, MyObject.class);

But brace yourself for JsonProcessingException challenges that may arise during this voyage.

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