使用 SerializerFeature.WriteNullStringAsEmpty 解决

   List<HistoryVector> historyVectors= new ArrayList<>();HistoryVector historyVector = new HistoryVector();historyVector.setInput("1");historyVector.setReason("111111");historyVector.setResult(null);historyVectors.add(historyVector);System.out.println(JSON.toJSONString(historyVector));System.out.println(JSON.toJSONString(historyVector, SerializerFeature.WriteNullStringAsEmpty));

输出的信息

{"input":"1","reason":"111111"}
{"case_desc":"","input":"1","reason":"111111","result":""}

当然你也可以写成一个配置，无需在每个JSON.toJSONString里面添加参数，以下为fastjson SerializerFeature其他方法