Kotlin: XML and Annotation constructor mapper does not work

[VitaliiLebedynskyi]

About the Bug...

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of MyBatis.

• I have confirmed this bug reproduces without 3rd party extensions (e.g. mybatis-plus).

Database Version

MySql 8

JDBC Driver Version

Maria driver 3.5.6

Issue Description

I am using kotlin and MyBatis for my project.
I found that i am not able to use constructor mapping. Issue mostly related to Kotlin Data classes support.

Inside the class

public class DefaultObjectFactory implements ObjectFactory, Serializable {
    private <T> T instantiateClass(Class<T> type, List<Class<?>> constructorArgTypes, List<Object> constructorArgs) 
}

MyBatis calls type.getDeclaredConstructor(constructorArgTypes.toArray(new Class[0])) and it throws Exception in Kotlin.

I did a debug. I checked - The types and values are correct and their count is correct!

Applogize for pasted image but it is to complex to explain:

So we see that we have args, arg types and their count is fine.

The issue is that - it missatches constructor signature and constructorArgTypes.toArray(new Class[0])
If i cal type.getDeclaredConstructors() it returns a valid constructor. You can see it in screenshot.

And here is my class: (Same issue for BOTH. Data class and just a class)

class DBQuestTemplate(
    val pk: Int?,
    val uuid: String,
    val name: String,
    val startTime: LocalDateTime?,
    val endTime: LocalDateTime?,
    val refreshType: QuestRefreshType,
    val target: QuestTarget,
    val reward: List<QuestReward>,
    val image: String?,
    val enabled: Boolean,
    val restricted: Boolean,
    val questOrder: Int,
    val questGroup: Int,
)

The mapper is

<constructor>
            <idArg column="q_pk" javaType="int"/>
            <arg column="q_uuid" javaType="string"/>
            <arg column="q_name" javaType="string"/>
            <arg column="q_start_time" javaType="java.time.LocalDateTime"/>
            <arg column="q_end_time" javaType="java.time.LocalDateTime"/>
            <arg column="q_refresh_type" javaType="com.simple.games.data.model.QuestRefreshType"/>
            <arg column="q_target"
                 javaType="com.simple.games.data.model.QuestTarget"
                 typeHandler="com.simple.games.data.handler.QuestTargetHandler"/>
            <arg column="q_reward"
                 javaType="java.util.List"
                 typeHandler="com.simple.games.data.handler.QuestRewardListHandler"/>
            <arg column="q_image" javaType="string"/>
            <arg column="q_enabled" javaType="boolean"/>
            <arg column="q_restricted" javaType="boolean"/>
            <arg column="q_quest_order" javaType="int"/>
            <arg column="q_quest_group" javaType="int"/>
        </constructor>

And the error is:

java.lang.NoSuchMethodException: com.simple.games.data.model.DBQuestTemplate.<init>(java.lang.Integer,java.lang.String,java.lang.String,java.time.LocalDateTime,java.time.LocalDateTime,com.simple.games.data.model.QuestRefreshType,com.simple.games.data.model.QuestTarget,java.util.List,java.lang.String,java.lang.Boolean,java.lang.Boolean,java.lang.Integer,java.lang.Integer)

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• I checked the Preview and my report looks awesome! 👍

[VitaliiLebedynskyi]

I am not sure yet.. But i am working with my batis for last couople of month.. And everytime i face some magic issues.

And i think the issues in Nullable fields. If kotlin class has non nullable field. It is not able to match with Java nullable fields.

[jeffgbutler]

I write a lot of Kotlin code with MyBatis and usually don't have issues. But... Kotlin is a bit weird about nullable vs. nonnullable primitives and you need to use the correct MyBatis type aliases. I'm assuming this is the problem you are facing. The last four fields in your class are actual Java primitives, so you need to use different type aliases. Here's a short table for reference:

Kotlin Type	Java Type	MyBatis Alias
Int	int	_int
Int?	Integer	int
Boolean	boolean	_boolean
Boolean?	Boolean	boolean

So I think your mapper should look like this:

<constructor>
  <idArg column="q_pk" javaType="int"/>
  <arg column="q_uuid" javaType="string"/>
  <arg column="q_name" javaType="string"/>
  <arg column="q_start_time" javaType="java.time.LocalDateTime"/>
  <arg column="q_end_time" javaType="java.time.LocalDateTime"/>
  <arg column="q_refresh_type" javaType="com.simple.games.data.model.QuestRefreshType"/>
  <arg column="q_target"
                 javaType="com.simple.games.data.model.QuestTarget"
                 typeHandler="com.simple.games.data.handler.QuestTargetHandler"/>
  <arg column="q_reward"
                 javaType="java.util.List"
                 typeHandler="com.simple.games.data.handler.QuestRewardListHandler"/>
  <arg column="q_image" javaType="string"/>
  <arg column="q_enabled" javaType="_boolean"/>
  <arg column="q_restricted" javaType="_boolean"/>
  <arg column="q_quest_order" javaType="_int"/>
  <arg column="q_quest_group" javaType="_int"/>
</constructor>

[VitaliiLebedynskyi]

But the actual issue is related to

<arg column="q_target"
                 javaType="com.simple.games.data.model.QuestTarget"
                 typeHandler="com.simple.games.data.handler.QuestTargetHandler"/>
  <arg column="q_reward"
                 javaType="java.util.List"
                 typeHandler="com.simple.games.data.handler.QuestRewardListHandler"/>

I have moved it out of consrtuctor and using result map like this:

    <resultMap id="DBQuestTemplateResultMapper" type="com.simple.games.data.model.DBQuestTemplate">
        <id property="pk" column="q_pk"/>
        <result property="uuid" column="q_uuid"/>
        <result property="name" column="q_name"/>
        <result property="startTime" column="q_start_time"/>
        <result property="endTime" column="q_end_time"/>
        <result property="refreshType" column="q_refresh_type"/>
        <result property="image" column="q_image"/>
        <result property="enabled" column="q_enabled"/>
        <result property="questType" column="q_quest_type"/>
        <result property="questOrder" column="q_quest_order"/>
        <result property="questGroup" column="q_quest_group"/>

        <result property="target"
                column="q_target"
                typeHandler="com.simple.games.data.handler.QuestTargetHandler"/>

        <result property="reward"
                column="q_reward"
                typeHandler="com.simple.games.data.handler.QuestRewardListHandler"/>

        <association property="localization"
                     javaType="com.simple.games.data.model.DbLocalization"
                     resultMap="com.simple.games.data.dao.LocalizationDao.LocalizationResultMapper"/>
    </resultMap>

and it works fine.

And the class is

data class DBQuestTemplate(
    val pk: Int?,
    val uuid: String,
    val name: String,
    val startTime: LocalDateTime?,
    val endTime: LocalDateTime?,
    val refreshType: QuestRefreshType,
    val image: String?,
    val enabled: Boolean,
    val questType: QuestType,
    val questOrder: Int,
    val questGroup: Int,
) {
    // TODO move out here. Temp solution?
    lateinit var target: QuestTarget
    lateinit var reward: List<QuestReward>
    var localization: DbLocalization? = null
}

[jeffgbutler]

Please make a small project that reproduces the issue, then I will take a look. There are examples of how to do that here: https://github.com/harawata/mybatis-issues

[jeffgbutler]

I maintain a library of examples using MyBatis with Kotlin. I just added an example using explicit constructor mappings - using both annotations and XML.

The repo is here: https://github.com/jeffgbutler/mybatis-kotlin-examples

The specific example for explicit constructor mappings is here: https://github.com/jeffgbutler/mybatis-kotlin-examples/tree/master/src/main/kotlin/example07

Hope this will help.

[VitaliiLebedynskyi]

@jeffgbutler

It works. Thanks a lot.. My mistake - did not read documentation clearly.. Maybe you can add a link to kotlin doc in Essentials block.. Thank you. It could be closed