SerializeConfig config = new SerializeConfig();
// 设置序列化为下划线
config.propertyNamingStrategy = PropertyNamingStrategy.SnakeCase;
String content = JSON.toJSONString(contentMap, config, SerializerFeature.WriteNullNumberAsZero, SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteNullStringAsEmpty, SerializerFeature.WriteNullBooleanAsFalse);
PropertyNamingStrategy参数