spring-boot - 如何使用Binder反序列化为Kotlin数据类？

Question

我使用的是 SpringBoot2.0.0.RELEASE，Kotlin 1.2.30，Java9。

我在配置文件中有如下配置:

test:
  user:
    id: 111
    username: 111
    password: 111
    addtime: 2018-11-11 11:11:11

User.kt代码如下:

data class User(
        val id: String,
        val username: String,
        val password: String,
        val addtime: LocalDateTime
) : Serializable

我尝试使用以下代码读取配置:

Binder.get(this.context.environment)
        .bind("test.user", User::class)
        .orElse(null)

但是，它没有成功并返回以下错误:

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [demo.User]: Illegal arguments for constructor; nested exception is java.lang.IllegalArgumentException: No argument provided for a required parameter: parameter #0 id of fun <init>(kotlin.String, kotlin.String, kotlin.String, java.time.LocalDateTime): demo.User
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:179)
    at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:124)
    at org.springframework.boot.context.properties.bind.JavaBeanBinder$Bean.lambda$getSupplier$0(JavaBeanBinder.java:173)
    at org.springframework.boot.context.properties.bind.JavaBeanBinder$BeanSupplier.get(JavaBeanBinder.java:227)
    at org.springframework.boot.context.properties.bind.JavaBeanBinder$BeanProperty.lambda$getValue$0(JavaBeanBinder.java:303)
    ... 80 more

完整错误日志:https://gist.github.com/Cat7373/174b0ddaf103b35062e7b03982f8cb38

我怎样才能成功？感谢您的帮助。

Answer 1

也许这个引用会有所帮助，尝试在定义数据类时添加 @PersistentConstructor 注释:Spring constructor annotations on Kotlin data class with default values或者，尝试为每个属性设置默认值。例如:

data class User(
    val id: String = "",
    val username: String = "",
    val password: String = "",
    val addtime: LocalDateTime = LocalDateTime.now()
) : Serializable