Spring+Kotlin环境下如何用配置动态值替换硬编码表名？

场景与问题 #

使用Spring + Kotlin开发Web应用，现有MyBatis Mapper及表定义类如下：

MyEntityMapper代码 #

@Mapper
@Repository
interface MyEntityMapper {
    /**
     * Поиск MyEntity.
     *
     * @param selectStatement Параметры запроса.
     * @return List MyEntity.
     */
    @SelectProvider(type = SqlProviderAdapter::class, method = "select")
    @Results(
        id = "myEntityMap",
        value = [
            Result(property = "name", column = "NAME"),
            Result(property = "price", column = "PRICE"),
            Result(property = "age", column = "AGE")
        ]
    )
    fun findListBy(selectStatement: SelectStatementProvider): List<MyEntity>

    /**
     * Обновление MyEntity.
     *
     * @param updateStatement MyEntity
     * @return Количество обновленных записей.
     */
    @UpdateProvider(type = SqlProviderAdapter::class, method = "update")
    fun update(updateStatement: UpdateStatementProvider): Int
}

fun MyEntityMapper.selectMany(completer: SelectCompleter) =
    selectList(this::findListBy, myEntity_.all, myEntity, completer)

fun MyEntityMapper.update(completer: UpdateCompleter) =
    update(this::update, MyEntity_, completer)

MyEntity_表定义类（非Spring组件） #

class MyEntity_ : SqlTable("my_entity") {
    val name = column<String>(name = "NAME", jdbcType = VARCHAR)
    val price = column<String>(name = "PRICE", jdbcType = VARCHAR)
    val age = column<String>(name = "AGE", jdbcType = VARCHAR)

    val all = listOf(
        name,
        price,
        age
    )

    companion object {
        val myEntity_ = MyEntity_()
    }
}

当前核心问题：class MyEntity_ : SqlTable("my_entity")中的表名"my_entity"为硬编码，希望替换为application.properties中的配置值；同时想了解Spring中如何为接口注入动态值。

一、动态替换表名的实现方案 #

方案1：将MyEntity_转为Spring组件，通过构造函数注入表名 #

修改MyEntity_类，移除静态单例，通过@Value注入配置中的表名：

@Component
class MyEntity_(@Value("\${table.names.my_entity}") tableName: String) : SqlTable(tableName) {
    val name = column<String>(name = "NAME", jdbcType = VARCHAR)
    val price = column<String>(name = "PRICE", jdbcType = VARCHAR)
    val age = column<String>(name = "AGE", jdbcType = VARCHAR)

    val all = listOf(name, price, age)
}

在application.properties中添加配置：

table.names.my_entity=my_entity

后续使用时，通过Spring的@Autowired注入MyEntity_实例，修改原扩展函数：

fun MyEntityMapper.selectMany(myEntity_: MyEntity_, completer: SelectCompleter) =
    selectList(this::findListBy, myEntity_.all, myEntity, completer)

方案2：通过配置类创建MyEntity_实例（不修改类本身为组件） #

如果不想将MyEntity_标记为Spring组件，可通过配置类动态传入表名：

首先修改MyEntity_构造函数：

class MyEntity_(tableName: String) : SqlTable(tableName) {
    val name = column<String>(name = "NAME", jdbcType = VARCHAR)
    val price = column<String>(name = "PRICE", jdbcType = VARCHAR)
    val age = column<String>(name = "AGE", jdbcType = VARCHAR)

    val all = listOf(name, price, age)
}

创建配置类提供Bean：

@Configuration
class TableConfig {
    @Value("\${table.names.my_entity}")
    private lateinit var myEntityTableName: String

    @Bean
    fun myEntity_(): MyEntity_ {
        return MyEntity_(myEntityTableName)
    }
}

同样在application.properties中配置表名，使用时通过@Autowired注入MyEntity_实例即可。

二、Spring中为接口注入动态值的方法 #

接口无法直接实例化，需通过以下方式实现动态值注入：

方法1：为接口编写实现类，注入动态值 #

定义接口后，创建Spring管理的实现类，在实现类中注入配置值：

interface TableNameProvider {
    fun getMyEntityTableName(): String
}

@Component
class TableNameProviderImpl(@Value("\${table.names.my_entity}") private val tableName: String) : TableNameProvider {
    override fun getMyEntityTableName(): String {
        return tableName
    }
}

后续在需要的地方注入TableNameProvider接口即可获取动态值。

方法2：结合MyBatis Provider注入动态值（针对Mapper场景） #

如果需要在MyBatis的Provider类中使用动态值，可将Provider类转为Spring组件，注入配置值：

@Component
class SqlProviderAdapter {
    @Value("\${table.names.my_entity}")
    private lateinit var myEntityTableName: String

    fun select(selectStatement: SelectStatementProvider): String {
        // 动态拼接SQL时使用myEntityTableName
        return "SELECT NAME, PRICE, AGE FROM $myEntityTableName ${selectStatement.whereClause}"
    }
}

注意确保MyBatis能识别Spring管理的Provider类，可通过@MapperScan配置或在Mapper的@SelectProvider中指定Spring Bean的名称。

内容的提问来源于stack exchange，提问作者Pavel Bukhalov