jackson entities turn json is NULL or empty does not participate in the serialization [Reserved]

Original blog: https://www.cnblogs.com/yangy608/p/3936848.html

 

1. entities

/**
 * The marked on the attribute, the attribute is NULL if not involved in the sequence of
 * If the top in the class, and that all the properties of this class of work
 * Include.Include.ALWAYS 默认
 * Include.NON_DEFAULT not attribute to the default value of the sequence
 * Include.NON_EMPTY property is empty ( "") is NULL or not serialized
 * Include.NON_NULL property is not serialized NULL
 */
@JsonInclude(Include.NON_NULL)

 

2. On the code

ObjectMapper mapper = new ObjectMapper();

/**
 * Set the mapper objects through this method, all the objects will be serialized serialized change rules 
 * Include.Include.ALWAYS 默认 
 * Include.NON_DEFAULT not attribute to the default value of the sequence 
 * Include.NON_EMPTY property is empty ( "") is NULL or not serialized 
 * Include.NON_NULL property is not serialized NULL 
 */
mapper.setSerializationInclusion(Include.NON_NULL);

User user = new User(1,"",null);
String outJson = mapper.writeValueAsString(user);
System.out.println(outJson);

 

Note: Only for VO work, Map List does not work, for example:

ObjectMapper mapper = new ObjectMapper();
mapper.setSerializationInclusion(Include.NON_NULL);
 
Map map = new HashMap();
map.put("a", null);
map.put("b", "b");
 
String ret_val = mapper.writeValueAsString(map);
System.err.println (ret_val);
Map m = mapper.readValue(ret_val, Map.class);
System.err.println(m.get("a") + "|" + m.get("b"));

Output:

{"b":"b","a":null}

null|b

 

VO = the new VO ();
vo.setA ( null );
vo.setB("b");
         
String ret_val1 = mapper.writeValueAsString(vo);
System.err.println (ret_val1);
VO v = mapper.readValue (ret_val1, VO. Class );
System.err.println(v.getA() + "|" + v.getB());<br>

Output:

{"b":"b"}

|b

 

 

 

 

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