1. Overview

This quick tutorial will show how to use Jackson 2 to convert a JSON String to a JsonNode (com.fasterxml.jackson.databind.JsonNode).

If you want to dig deeper and learn other cool things you can do with the Jackson 2 – head on over to the main Jackson tutorial.

2. Quick Parsing

Very simply, to parse the JSON String we only need an ObjectMapper:

@Test public void whenParsingJsonStringIntoJsonNode_thenCorrect() throws JsonParseException, IOException { String jsonString = "{"k1":"v1","k2":"v2"}"; ObjectMapper mapper = new ObjectMapper(); JsonNode actualObj = mapper.readTree(jsonString); assertNotNull(actualObj); }

3. Low Level Parsing

If, for some reason, you need to go lower level than that, the following example exposes the JsonParser responsible with the actual parsing of the String:

@Test public void givenUsingLowLevelApi_whenParsingJsonStringIntoJsonNode_thenCorrect() throws JsonParseException, IOException { String jsonString = "{"k1":"v1","k2":"v2"}"; ObjectMapper mapper = new ObjectMapper(); JsonFactory factory = mapper.getFactory(); JsonParser parser = factory.createParser(jsonString); JsonNode actualObj = mapper.readTree(parser); assertNotNull(actualObj); }

4. Using the JsonNode

After the JSON is parsed into a JsonNode Object, we can work with the Jackson JSON Tree Model:

@Test public void givenTheJsonNode_whenRetrievingDataFromId_thenCorrect() throws JsonParseException, IOException { String jsonString = "{"k1":"v1","k2":"v2"}"; ObjectMapper mapper = new ObjectMapper(); JsonNode actualObj = mapper.readTree(jsonString); // When JsonNode jsonNode1 = actualObj.get("k1"); assertThat(jsonNode1.textValue(), equalTo("v1")); }

5. Conclusion

This article illustrated how to parse JSON Strings into the Jackson JsonNode model to enable a structured processing of the JSON Object.

The implementation of all these examples and code snippets can be found in my github project – this is an Eclipse based project, so it should be easy to import and run as it is.