java jackson库各对象之间转换

java对象 到 json字符串

Model model = new Model();
model.setAge(25);
List<Model> models = new ArrayList<Model>();
models.add(models);
ObjectMapper mapper = new ObjectMapper(); 
mapper.writeValueAsString(model);
mapper.writeValueAsString(models);

java对象 到 jsonNode、objectNode、arrayNode对象

jsonNode <- json string <- java object

json字符串 到 java对象

String json = "{\"age\" : 25}";
ObjectMapper mapper = new ObjectMapper(); 
Model model = mapper.readValue(json, Model.class);
String json2 = "[{\"age\" : 25}]";
Model models = mapper.readValue(json2, new TypeReference<List<Model>>);

json字符串 到 jsonNode、objectNode、arrayNode对象

String json = "{\"age\" : 25}";
String json2 = "[{\"age\" : 25}]";
ObjectMapper mapper = new ObjectMapper();  
JsonNode jsonNode = mapper.readTree(json); 
ObjectNode objectNode = (ObjectNode)jsonNode;
JsonNode jsonNode = mapper.readTree(json2); 
ArrayNode arrayNode = (ArrayNode)jsonNode;  //if is array object

jsonNode等对象 到 json字符串

ObjectMapper mapper = new ObjectMapper(); 
mapper.writeValueAsString(jsonNode);
mapper.writeValueAsString(arrayNode);

jsonNode等对象 到 java对象

jsonNode -> json string -> java object

class Model {
  private int age;
  
  public void setAge(int age){
    this.age = age;
  }

  public int getAge(){
    return age;
  }
}