java - Kotlin - Jackson 忽略空值

Question

我在使用 Jackson 解析 JSON 时遇到了问题，我想忽略 null 属性。这是我的代码。

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
data class ParsedSurvey(
    val items: List<ParsedSurveyItem> = listOf()
)

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
data class ParsedSurveyItem(
    val type: String = "",
    val text: String = "",
    val instructions: String = "",
    val prog: String = "",
    val `var`: String = "",
    val columns: List<ParsedSurveyAnswer> = listOf(),
    val rows: List<ParsedSurveyAnswer> = listOf(),
    val num: String = "",
    val multi: Boolean = false,
    val random: Boolean = false,
    val min: Int = -1,
    val max: Int = -1,
    val recordOrder: Boolean = false,
    val rowLength: Int = -1
)

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
data class ParsedSurveyAnswer @JsonCreator(mode = JsonCreator.Mode.PROPERTIES) constructor(
    val text: String = "",
    val prog: String = "<p></p>",
    @JsonProperty("isOpen") val isOpen: Boolean = false
)

如果我尝试将 ParsedSurveyItem 中的行属性设置为 null。我收到此错误:

value failed for JSON property rows due to missing (therefore NULL) value for creator parameter rows which is a non-nullable type.
Jackson doesn't ignore 

为什么 Jackson 解析空值？感谢您的帮助。

Answer 1

您可以设置行属性 null 只有当它可以为 null 时。它的意思是改成

 val rows: List<ParsedSurveyAnswer>? 

您还可以删除 listOf() & @JsonIgnoreProperties(ignoreUnknown = true)