尽管使用了Jackson-Module-Kotlin，但仍无法构建Kotlin数据类的实例

Question

我正在尝试对Kotlin数据类进行挑选，但是我会发现错误：

Exception in thread "main" com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `TestBean` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (String)"{"foo": "bar"}"; line: 1, column: 2]
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:63)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1432)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1062)
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1302)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:326)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:159)
    at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:1719)
    at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1261)
    at MainKt.main(Main.kt:13)

这是代码：

fun main(args: Array<String>) {
    ObjectMapper().registerKotlinModule()
        .readerFor(TestBean::class.java)
        .readValue<TestBean>("{\"foo\": \"bar\"}");
}

data class TestBean(private val foo: String)

和依赖项：

<dependencies>
    <dependency>
        <groupId>org.jetbrains.kotlin</groupId>
        <artifactId>kotlin-stdlib-jdk8</artifactId>
        <version>1.6.21</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.module</groupId>
        <artifactId>jackson-module-kotlin</artifactId>
        <version>2.10.5</version>
        <scope>compile</scope>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.10.5</version>
        <scope>compile</scope>
    </dependency>
</dependencies>

Answer 1

问题是私有属性foo。您可以将其公开或使用@jsonproperty使其正常工作

data class TestBean(@JsonProperty("foo") private val foo: String)