Boolean property name starting with 'is' not serialized/deserialized properly

[tbvh]

Hi,
I'm experiencing issues with a boolean property which name starts with 'is'.
While the getter doesn't get prefixed by kotlin, it seems that jackson still strips away 'is' as though it was a prefix. The resulting json doesn't contain the 'is', and deserialization fails.

This test illustrates the problem:

class SerializationTest {
    @Test
    fun testIsBool() {
        val mapper = ObjectMapper()
        mapper.registerModule(KotlinModule())

        val example = IsBoolExample(true)
        val json = mapper.writeValueAsString(example) 
        // json contains: {"trueOrFalse":true}

        val deserialized = mapper.readValue(json, IsBoolExample::class.java)

        Assert.assertEquals(example.isTrueOrFalse, deserialized.isTrueOrFalse)
    }
}
class IsBoolExample(val isTrueOrFalse: Boolean)

This fails on mapper.readValue(..) with:

com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.bol.service.reptile.spring.IsBoolExample: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
at [Source: {"trueOrFalse":true}; line: 1, column: 2]

[tbvh]

Note that the following test succeeds as expected:

class SerializationTest {
    @Test
    fun testBool() {
        val mapper = ObjectMapper()
        mapper.registerModule(KotlinModule())

        val example = BoolExample(true)
        val json = mapper.writeValueAsString(example)
        // json contains: {"trueOrFalse":true}

        val deserialized = mapper.readValue(json, BoolExample::class.java)

        Assert.assertEquals(example.trueOrFalse, deserialized.trueOrFalse)
    }
}
class BoolExample(val trueOrFalse: Boolean)

And finally, if another field is present (so a constructor can be matched) and FAIL_ON_UNKNOWN_PROPERTIES is false, then the boolean parameter stays (defaults to) false.

class SerializationTest {
    @Test
    fun testStrIsBoolExample() {
        val mapper = ObjectMapper()
        mapper.registerModule(KotlinModule())
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)

        val example = StrIsBoolExample(true, "example")
        val json = mapper.writeValueAsString(example)
        // json contains: {"str":"example","trueOrFalse":true}

        val deserialized = mapper.readValue(json, StrIsBoolExample::class.java)

        Assert.assertEquals(example.isTrueOrFalse, deserialized.isTrueOrFalse)
    }
}
class StrIsBoolExample(val isTrueOrFalse: Boolean,val str: String)

Here the assert fails.

[hizhengfu]

Encountered the same problem,
It was also found that pId was serialized to pid

[DavidRigglemanININ]

I'm seeing this issue as well. One thing I noticed is that if I flip the val to a var, then it works as expected. So I'm guessing the issue is that the val generates a Java getter but not the setter, and that's what's causing the problem here.

[apatrida]

Jackson expects JavaBean naming patterns, Kotlin does not always generate things that way and therefore creates an unwinnable situation. I'm still looking at options, but there is a workaround for some cases.

This works by adding a JsonProperty annotation:

  @Test
    fun testGithub80_FailOnBoolWith_Is() {
        val mapper = jacksonObjectMapper()

        val example = IsBoolExample(true)
        val json = mapper.writeValueAsString(example)
        // json contains: {"trueOrFalse":true}

        val deserialized = mapper.readValue<IsBoolExample>(json)

        assertEquals(example.isTrueOrFalse, deserialized.isTrueOrFalse)
    }

    class IsBoolExample(@JsonProperty("trueOrFalse") val isTrueOrFalse: Boolean)

[raderio]

If in Kotlin I have
class IsBoolExample(val isTrueOrFalse: Boolean)
I expect to have isTrueOrFalse in json, not trueOrFalse, if I need trueOrFalse I will have trueOrFalse property in class.

So I think it will be ok to add @JsonProperty with values for boolean properties by default by jackson-module-kotlin, or at least to be configurable by property in module.

[jdorleans]

I have a similar problem for Boolean property when its name starts with is*. In my case, it is already a var and it doesn't work as mentioned above. The only trivial way I found was to add @JsonProperty, since I want its name to be recognised as it is and not configure the module to ignore it.
Here's my example:

class Product {
  var isNew: Boolean? = null
}
...
val map = mapOf("isNew" to true) // Deserialized Product JSON in a Map<String, Any?>
mapper.convertValue(map, Product::class.java) // FAIL 

The error message says property isNew is not recognised and the only known property is called: new.

[dynamics3]

We have encountered this thing as well. When we receive json that has a boolean, which starts with "is", then it fails on jacksonObjectMapper().readValue<TestData>(jsonString) throwing UnrecognizedPropertyException. Example: data class TestData(val isOk: Boolean = false)

The funny thing is that when another property is added to data class, then it works flawlessly, e.g.
data class TestData(val addedProp: String = "", val isOk: Boolean = false).

Adding @get:JsonProperty("isOk") annotation fixes the issue. However, it would be great if the appropriate solution is added.

[ahmetgeymen]

I have also encountered with this issue with my String property. I overcame with using annotation @get:JsonProperty("isSomething"). Though I think we should not use any annotation, Jackson should serialize properly.

See also:
(#52)

[sschuberth]

Another incarnation of the problem seems to be that @JsonIgnore does not work on such properties. For code

@JsonIgnore
val isWholeProjectExcluded = true

the property still gets serialized (as "wholeProjectExcluded").

A work-around is to write the code as

val isWholeProjectExcluded
        @JsonIgnore
        get() = true

or shorter, as @Tapac points out, as

@get:JsonIgnore
val isWholeProjectExcluded = true

[tjsnell]

Just wasted a bunch of time tracking this down. Any plans to fix it?

[Tapac]

@sschuberth, you can use get as annotation target (see more here)
@get:JsonIgnore val isWholeProjectExcluded = true