A solution where the Null attribute is not shown when fastjson generates json

For example

Map < String , Object > jsonMap = new HashMap< String , Object>(); 
jsonMap.put("a",1); 
jsonMap.put("b",""); 
jsonMap.put("c",null); 
jsonMap.put("d","wuzhuti.cn"); 
 
String str = JSONObject.toJSONString(jsonMap); 
System.out.println(str); 
// The output :{"a":1,"b":"",d:"wuzhuti.cn"} 

It can be seen from the output that the corresponding key of null has been filtered out. This is obviously not what we want, and we need to use the SerializerFeature serialization property of fastjson

This is the method: JSONObject.toJSONString(Object object, SerializerFeature... features)

SerializerFeature serialization property for Fastjson

QuoteFieldNames -- Whether double quotes are used when key is printed, the default is true

WriteMapNullValue -- Fields with output value null, default to false

WriteNullNumberAsZero -- If the value field is null, the output is 0 instead of null

The WriteNullListAsEmpty -- �List field is null and the output is [], not null

WriteNullStringAsEmpty - If the character type field is null, the output is "" instead of null

The WriteNullBooleanAsFalse Boolean field, if null, outputs false instead of null

code

Map < String , Object > jsonMap = new HashMap< String , Object>(); 
jsonMap.put("a",1); 
jsonMap.put("b",""); 
jsonMap.put("c",null); 
jsonMap.put("d","wuzhuti.cn"); 
 
String str = JSONObject.toJSONString(jsonMap,SerializerFeature.WriteMapNullValue); 
System.out.println(str); 
// The output :{"a":1,"b":"","c":null,"d":"wuzhuti.cn"}