Created
November 4, 2020 15:40
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Distinguish nulls and non-present values with Jackson, Optional<T>, and Kotlin
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| package testing | |
| import com.fasterxml.jackson.databind.ObjectMapper | |
| import org.junit.jupiter.api.Assertions.assertEquals | |
| import org.junit.jupiter.api.Test | |
| import java.util.* | |
| class TestJacksonWithOptional { | |
| val defaultObjectMapper = ObjectMapper().apply { | |
| findAndRegisterModules() | |
| // jackson-datatype-jdk8 is present | |
| // jackson-module-kotlin is present | |
| } | |
| data class Example( | |
| val greeting: Optional<String>? = null | |
| ) | |
| @Test | |
| fun `handles optional type with non-null value`() { | |
| val json = """{ "greeting": "hello" }""" | |
| val obj = defaultObjectMapper.readValue(json, Example::class.java) | |
| assertEquals("hello", obj.greeting?.get()) | |
| } | |
| @Test | |
| fun `handles optional type with null value`() { | |
| val json = """{ "greeting": null }""" | |
| val obj = defaultObjectMapper.readValue(json, Example::class.java) | |
| assertEquals(false, obj.greeting?.isPresent) | |
| } | |
| @Test | |
| fun `handles optional type with non-present value`() { | |
| val json = """{ }""" | |
| val obj = defaultObjectMapper.readValue(json, Example::class.java) | |
| assertEquals(null, obj.greeting) | |
| } | |
| } |
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This demo test code is for this stackoverflow question: https://stackoverflow.com/a/64683356/516910