JSONObject.toJSONString(Object object,SerializerFeature… features)

Fastjson的SerializerFeature序列化属性

QuoteFieldNames———-输出key时是否使用双引号,默认为true
WriteMapNullValue——–是否输出值为null的字段,默认为false
WriteNullNumberAsZero—-数值字段如果为null,输出为0,而非null
WriteNullListAsEmpty—–List字段如果为null,输出为[],而非null
WriteNullStringAsEmpty—字符类型字段如果为null,输出为”“,而非null
WriteNullBooleanAsFalse–Boolean字段如果为null,输出为false,而非nul

Map < String,Object > jsonMap = new HashMap< String,Object>(); 
jsonMap.put("a",1); 
jsonMap.put("b",""); 
jsonMap.put("c",null); 
jsonMap.put("d","dddddddddd"); 

String str = JSONObject.toJSONString(jsonMap,SerializerFeature.WriteMapNullValue); 
System.out.println(str); 
//输出结果:{"a":1,"b":"","c":null,"d":"dddddddddd"}