CODEWITHSUNDEEP
javajsonjackson
etang
etang

Reputation: 750

Json manipulation on top of Jackson

Jackson is great for translating between POJO and json strings. But it's a pain to use it for manipulating a json string. I find myself doing stuff like:

ObjectMapper mapper = new ObjectMapper();
JsonNode node = mapper.readTree(ReadFile("testObj.json"));
((ObjectNode)node).put("testField", "newTestValue");
TestObject obj = mapper.readValue(mapper.writeValueAsString(node), TestObject.class);

And this is the simple example. It gets more complicated if you want to add a new object or an array of things. Is there a better way to do this?

Upvotes: 1

Views: 5080

Answers (1)

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279880

I don't see what's so difficult. If you are certain your root JSON is a JSON object, simply cast the value returned by ObjectMapper#readTree(..) to an ObjectNode and manipulate it.

String json = "{\"sample\": \"some value\", \"nested\": {\"prop\": 123, \"nestedArray\":[1,2, \"string value\"], \"array\":[null, 42]}}";
ObjectNode node = (ObjectNode) new ObjectMapper().readTree(json);
System.out.println(node);
ArrayNode arrayNode = node.putArray("new array");
arrayNode.add(true).add(1).add("new value"); // chain add calls
arrayNode.addObject().put("nestedInArray", "nested object value"); // add an object and add to it
System.out.println(node);

prints

{"sample":"some value","nested":{"prop":123,"nestedArray":[1,2,"string value"],"array":[null,42]}}
{"sample":"some value","nested":{"prop":123,"nestedArray":[1,2,"string value"],"array":[null,42]},"new array":[true,1,"new value",{"nestedInArray":"nested object value"}]}

Note that you can also add your custom objects too. They will typically be wrapped in POJONode objects.

Upvotes: 3

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