java：fastjson生成json字符串时null属性不显示（value为null，则键不显示问题）

案例

Map fastJsonMap = new HashMap();
	List nullList = null;
	List emptyList = new ArrayList();
	fastJsonMap.put("num", 1);
	fastJsonMap.put("emptyStr", "");
	fastJsonMap.put("nullValue", null);
	fastJsonMap.put("str", "baidu.com");
	fastJsonMap.put("nullList", nullList);
	fastJsonMap.put("emptyList", emptyList);

	String str = JSONObject.toJSONString(fastJsonMap);

输出结果

{"str":"baidu.com","emptyList":[],"emptyStr":"","num":1}

修改

String str = JSONObject.toJSONString(fastJsonMap,
            SerializerFeature.WriteMapNullValue,
            SerializerFeature.WriteNullListAsEmpty);

输出结果

{"str":"baidu.com","emptyList":[],"emptyStr":"","num":1,"nullValue":null,"nullList":null}

• 1

SerializerFeature属性

枚举值	解释
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null