[JSON <-> Java Object] JSON Reading and Writing Using ObjectMapper #jackson #spring #spring_boot #json

java_json.java

// jackson package

//JSON to Java
String json = "{ \"color\" : \"Black\", \"type\" : \"BMW\" }";
ObjectMappper mapper = new ObjectMapper();
// readValue throws IOException, com.fasterxml.jackson.core.JsonParseException, 
// JsonMappingException
JavaObject object = mapper.readValue(json, JavaObject.class);

//Java to JSON
String jsonStr = mapper.writeValueAsString(object);

//JSON array to Java List
String jsonCarArray = 
  "[{ \"color\" : \"Black\", \"type\" : \"BMW\" }, { \"color\" : \"Red\", \"type\" : \"FIAT\" }]";
List<Car> listCar = objectMapper.readValue(jsonCarArray, new TypeReference<List<Car>>(){});

//JSON to Java map
String json = "{ \"color\" : \"Black\", \"type\" : \"BMW\" }";
Map<String, Object> map = objectMapper.readValue(json, new TypeReference<Map<String,Object>>(){});

// JsonNode
String json = "{ \"color\" : \"Black\", \"type\" : \"FIAT\" }";
JsonNode jsonNode = objectMapper.readTree(json);
String color = jsonNode.get("color").asText();

// JSON Array to POJO List
String jsonStr = "[{\"first\": \"alex\", \"last\": \"hou\"}," +
                      "{\"first\": \"mike\", \"last\": \"xie\"}]";

ObjectMapper mapper = new ObjectMapper();
List<People> peopleList = mapper.readValue(jsonStr,
                    mapper.getTypeFactory().constructCollectionType(List.class, People.class));