When jackson object is converted to json, It is NULL and does not participate in serialization summary. jacksonjson

When jackson object is converted to json, It is NULL and does not participate in serialization summary. jacksonjson

Add dependency first
<Dependency>
<GroupId> com. google. code. gson </groupId>
<ArtifactId> gson </artifactId>
</Dependency>

Method 1: Use @ JsonInclude (JsonInclude. Include. NON_NULL) on the object)

1. if it is placed on an attribute, if it is NULL, it is not involved in serialization;
2. If it is placed on the class, it will take effect for all the attributes of the class;

Parameter meaning:
JsonInclude. Include. ALWAYS default
JsonInclude. Include. NON_DEFAULT attribute is default value not serialized
The JsonInclude. Include. NON_EMPTY attribute is NULL ("") or NULL is not serialized.
The property of JsonInclude. Include. NON_NULL is NULL and is not serialized.

Before use

After use

Method 2: If you do not want to add such a configuration every time, you can configure a global definition in application. yml, which takes effect by default.

spring:   jackson:        default-property-inclusion: non_null

 

Method 3: set through the ObjectMapper object. The following is a test case.

@ Testpublic void test () throws JsonProcessingException {ResultVo resultVo = new ResultVo (); resultVo. setCode (0); resultVo. setMsg ("succeeded"); ObjectMapper mapper = new ObjectMapper (); mapper. setserializationsion Sion (JsonInclude. include. ALWAYS); // default String json = mapper. writeValueAsString (resultVo); System. out. println (json); mapper = new ObjectMapper (); mapper. setserializationsion Sion (JsonInclude. include. NON_NULL); // The property is NULL. json = mapper is not serialized. writeValueAsString (resultVo); System. out. println (json); Map map = new HashMap (); map. put ("code", 0); map. put ("msg", "successful"); map. put ("data", null); json = mapper. writeValueAsString (map); System. out. println (json );}

Print as follows:

{"Code": 0, "msg": "successful", "data": null} {"code": 0, "msg ": "successful"} {"msg": "successful", "code": 0, "data": null}

Note: ObjectMapper only works for VO and does not work for Map List.

 

1. If a field must be returned, you can give the default value (such as string ""; list []) at the beginning of the object class to avoid null.

2. When the jackson object is converted to json, @ JsonIgnore is used to place an attribute on this attribute when it is not serialized.