Structure

this blog introduce 3 ways using mybatis

• based on annotationed SQL and Query interfaces : suppored by MyBatis framework

• based on Query Wrapper : supported by MyBatis Plus framework

  MyBatis Plus provides a easier way to dynamically set condition and updated fields

• base on Query Condition : combined MyBatis Plus and Kotlin, so called MyBatis++

  MyBatis++ provides a more easier way to build complicated conditions

  and supports update values through an Example bean

MyBatis++ Controller Abilities

this controller present multiple ways to do CURD with MyBatis++

you can choose your favorite ones or those match your current project most comfortably

package x.spring.hello.controller

import org.springframework.beans.factory.annotation.Autowired
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RestController
import x.kotlin.commons.serialize.JSON.toJson
import x.kotlin.commons.serialize.JSON.toJsonOrNull
import x.kotlin.commons.string.UUID
import x.spring.hello.model.User
import x.spring.hello.model.UserExample
import x.spring.hello.repository.UserMapper
import x.spring.hello.mybatis.*

@RestController
class UserController {

    @Autowired
    private lateinit var userMapper: UserMapper

    @GetMapping("/01")
    fun selectAll(): String {
        val userList = userMapper.selectAll()
        return userList.toJson()
    }

    @GetMapping("/02")
    fun selectByName(): String {
        val user = userMapper.selectUserByName("Jimmy")
        return user.toJsonOrNull().orEmpty()
    }

    @GetMapping("/03")
    fun selectByCondition(): String {
        val condition = condition { it.eq(User::name, "Jimmy") }
        val users = userMapper.selectList(condition.build())
        return users.toJson()
    }

    @GetMapping("/04")
    fun insert(): String {
        val user = User()
        user.name = UUID.short()
        userMapper.insert(user)
        return user.toJson()
    }

    @GetMapping("/05")
    fun insertOrUpdate(): String {
        val user = User()
        user.id = "1"
        user.name = UUID.short()
        userMapper.insertOrUpdate(user)
        return user.toJson()
    }

    @GetMapping("/06")
    fun updateByCondition(): String {
        val cond1 = condition { it.isNotNull(User::id) }
        val cond2 = condition { it.eq(User::name, "Jimmy") }
        val cond3 = condition { it.gt(User::age, 15) }
        val cond4 = condition {
            it.set(User::name, "Jimmy")
            it.set(User::age, 18)
        }
        val condition = cond1 and cond2 and cond3 attributes cond4
        val count = userMapper.update(condition.build())
        return count.toJson()
    }

    @GetMapping("/07")
    fun updateByEntityAndCondition(): String {
        val entity = User()
        entity.name = "Updated"
        entity.age = 36
        val cond1 = condition { it.isNotNull(User::id) }
        val cond2 = condition { it.like(User::name, "Jimmy") }
        val cond3 = condition { it.gt(User::age, 35) }
        val condition = cond1 and (cond2 or cond3)
        val count = userMapper.update(entity, condition.build())
        return count.toJson()
    }

    @GetMapping("/08")
    fun updateByExampleAndCondition(): String {
        val example = UserExample()
        example.age = 18
        val cond1 = condition { it.isNotNull(User::id) }
        val cond2 = condition { it.like(User::name, "Jimmy") }
        val cond3 = condition { it.gt(User::age, 35) }
        val condition = cond1 and (cond2 or cond3) values example
        val count = userMapper.update(condition.build())
        return count.toJson()
    }

    @GetMapping("/09")
    fun selectCrossTables(): String {
        val userRoles = userMapper.selectUserRole()
        return userRoles.toJson()
    }
}

Configure Plugins and Repositories

pluginManagement {
    repositories {
        gradlePluginPortal()
        google()
        mavenCentral()
    }
}

dependencyResolutionManagement {
    repositoriesMode = RepositoriesMode.PREFER_SETTINGS
    repositories {
        gradlePluginPortal()
        google()
        mavenCentral()
    }
}

buildscript {
    repositories {
        gradlePluginPortal()
        google()
        mavenCentral()
    }
}

plugins {
    id("org.jetbrains.kotlin.jvm") version "2.0.21" apply false
    id("org.jetbrains.kotlin.kapt") version "2.0.21" apply false
    id("org.jetbrains.kotlin.plugin.spring") version "2.0.21" apply false
    id("org.springframework.boot") version "3.4.1" apply false
}

include("spring-mybatis")

Apply Plugins and Add Dependencies

plugins {
    id("org.jetbrains.kotlin.jvm")
    id("org.jetbrains.kotlin.kapt")
    id("org.jetbrains.kotlin.plugin.spring")
    id("org.springframework.boot")
}

java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

dependencies {
    val springBootVersion = "3.4.1"
    val springCloudVersion = "4.2.0"
    val springCloudAlibabaVersion = "2023.0.3.2"
    // commons
    api("io.github.hellogoogle2000:kotlin-commons:1.0.19")
    // kotlin
    api("org.jetbrains.kotlin:kotlin-reflect:2.0.21")
    // spring
    api("org.springframework.boot:spring-boot-starter:$springBootVersion")
    api("org.springframework.boot:spring-boot-starter-web:$springBootVersion")
    api("org.springframework.cloud:spring-cloud-starter-bootstrap:$springCloudVersion")
    // mybatis
    api("link.thingscloud:quick-spring-boot-starter-mybatis-plus:2025.01.22")
}

MyBatis++ Spring Properties

# service
server.port=10003
spring.application.name=mybatis
spring.profiles.active=dev
spring.devtools.add-properties=false
# mybatis
spring.datasource.username=root
spring.datasource.password=123456789
spring.datasource.url=jdbc:mysql://localhost:3306/dev?characterEncoding=utf-8&serverTimezone=UTC

MyBatis++ Application

package x.spring.hello

import org.mybatis.spring.annotation.MapperScan
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication

@SpringBootApplication
@MapperScan(basePackages = ["x.spring.hello.repository"])
class MybatisApplication

fun main(args: Array<String>) {
    runApplication<MybatisApplication>(*args)
}

MyBatis++ Beans

package x.spring.hello.model

import com.baomidou.mybatisplus.annotation.IdType
import com.baomidou.mybatisplus.annotation.TableId

class User {

    @TableId(type = IdType.ASSIGN_UUID)
    var id = ""

    var name = ""

    var age = 0
}

package x.spring.hello.model

class UserExample {

    var id: String? = null

    var name: String? = null

    var age: Int? = null
}

package x.spring.hello.model

class UserRoleQueryResult {

    var name = ""

    var role = ""
}

MyBatis++ Mapper

mapper sometimes called interface, service or repository in other projects

package x.spring.hello.repository

import link.thingscloud.quick.mybatisplus.base.BaseMapper
import org.apache.ibatis.annotations.Select
import x.spring.hello.model.User
import x.spring.hello.model.UserRoleQueryResult

interface UserMapper : BaseMapper<User> {

    @Select("select * from user")
    fun selectAll(): MutableList<User>

    @Select("select * from user where name = #{name}")
    fun selectUserByName(name: String): User?

    @Select(
        """
          select 
            user.name as name,
            role.name as role 
          from user left join role
          on user.roleId = role.id
        """
    )
    fun selectUserRole(): List<UserRoleQueryResult>
}

MyBatis++ Query Builder

this is the core component to build query condition and examples

difference between entity and example is :

entity will update all field, while example only update non-null fields

package x.spring.hello.mybatis

import com.baomidou.mybatisplus.extension.kotlin.KtUpdateWrapper
import kotlin.reflect.KClass
import kotlin.reflect.KProperty1
import kotlin.reflect.full.memberProperties

fun interface ConditionConfigurator<T : Any> {
    fun configure(wrapper: KtUpdateWrapper<T>)
}

data class QueryCondition<T : Any>(
    val configurator: ConditionConfigurator<T>
)

inline fun <reified T : Any> QueryCondition<T>.build(): KtUpdateWrapper<T> {
    val wrapper = KtUpdateWrapper(T::class.java)
    configurator.configure(wrapper)
    return wrapper
}

inline fun <reified T : Any> condition(configurator: ConditionConfigurator<T>): QueryCondition<T> {
    return QueryCondition(configurator)
}

infix fun <T : Any> QueryCondition<T>.and(other: QueryCondition<T>): QueryCondition<T> {
    val configurator = ConditionConfigurator {
        configurator.configure(it)
        it.and { other.configurator.configure(it) }
    }
    return QueryCondition(configurator)
}

infix fun <T : Any> QueryCondition<T>.or(other: QueryCondition<T>): QueryCondition<T> {
    val configurator = ConditionConfigurator {
        configurator.configure(it)
        it.or { other.configurator.configure(it) }
    }
    return QueryCondition(configurator)
}

infix fun <T : Any> QueryCondition<T>.not(other: QueryCondition<T>): QueryCondition<T> {
    val configurator = ConditionConfigurator {
        configurator.configure(it)
        it.not { other.configurator.configure(it) }
    }
    return QueryCondition(configurator)
}

infix fun <T : Any> QueryCondition<T>.attributes(other: QueryCondition<T>): QueryCondition<T> {
    val configurator = ConditionConfigurator {
        configurator.configure(it)
        other.configurator.configure(it)
    }
    return QueryCondition(configurator)
}

inline infix fun <reified T : Any, reified S : Any> QueryCondition<T>.values(example: S): QueryCondition<T> {
    val configurator = ConditionConfigurator { wrapper ->
        configurator.configure(wrapper)
        val properties = S::class.memberProperties
        properties.forEach { propertyS ->
            val value = propertyS.get(example)
            value.takeIf { it != null } ?: return@forEach
            val property = T::class.findPropertyByName(propertyS.name)
            property.takeIf { it != null } ?: return@forEach
            wrapper.set(property, value)
        }
    }
    return QueryCondition(configurator)
}

inline fun <reified T : Any> KClass<T>.findPropertyByName(name: String): KProperty1<T, *>? {
    return memberProperties.firstOrNull { it.name == name }
}