使用com.fasterxml.jackson生成json空对象字符串

目标json样式

在项目中需要将java对象生成如下的json字符串

{"name":"akio","obj":{}}

相关Java类

public class User implements Serializable {    private String name;    private Object obj = new Object();    //getter/setter}

使用net.sf.json生成目标json字符串

public static void main(String[] args) throws Exception {    User user = new User();    user.setName("akio");    JSONObject json = JSONObject.fromObject(user);    System.out.println(json.toString());}

使用com.fasterxml.jackson生成目标json字符串

public static void main(String[] args) throws Exception {    User user = new User();    user.setName("akio");    ObjectMapper mapper = new ObjectMapper();    String jsonString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(user);    System.out.println(jsonString);}

结果报错：

Exception in thread "main" com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class java.lang.Object and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: cn.akioyuan.nulljsonobject.User["obj"])    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:269)....

根据提示，添加相应配置信息后，可生成空的json对象

ObjectMapper mapper = new ObjectMapper();mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);//设置为false

gradle dependencies

"net.sf.json-lib:json-lib:2.4:jdk15","com.fasterxml.jackson.core:jackson-core:2.7.4","com.fasterxml.jackson.core:jackson-databind:2.7.4",