在 Spring Boot / Kotlin 中自动装配泛型

Question

目前我有如下课程：

interface Mapper<IN, OUT> {
    fun map(input: IN): OUT
}

@Service
class ContractPhaseMapper: Mapper<Contract, List<ContractPhase>> {
    override fun map(input: Contract): List<ContractPhase> = contract.phases.map { 
        ContractPhase(...)
    }
}

@Service
class ContractPhaseProcessor(private val contractPhaseMapper: Mapper<Contract, List<ContractPhase>>) {
    fun createResponse(contracts: List<Contract>) = SomeResponse(
        contractPhases = contracts.map { contractPhaseMapper.map(it) }.flatten()
    )
}

不幸的是，这导致 Spring 退出并显示消息：

Parameter # of constructor in my.package.ContractPhaseProcessor required a bean of type 'my.package.mapper.Mapper' that could not be found.

如果我尝试像 Mapper<Contract, Customer> 这样的映射器，它会正常工作。

我也尝试使用@Qualifier 使其明确使用此服务，但它仍然不起作用。

有人知道这个问题的简单解决方案吗？

Answer 1

我无法弄清楚为什么您的方法不起作用 - 但我已经重现了您的问题并可以建议您解决方法：如果您使用 @Configuration 注释类而不是 @Service 注释来配置 Spring bean ，一切正常：

class ContractPhaseMapper: Mapper<Contract, List<ContractPhase>> {
    override fun map(input: Contract): List<ContractPhase> = ...
}

class ContractPhaseProcessor(private val contractPhaseMapper: Mapper<Contract, List<ContractPhase>>) {
    fun createResponse(contracts: List<Contract>) : String = ...
}

@Configuration
open class MyConfiguration {
    @Bean
    open fun mapper() : Mapper<Contract, List<ContractPhase>> = ContractPhaseMapper()

    @Bean
    open fun processor(mapper: Mapper<Contract, List<ContractPhase>>) : ContractPhaseProcessor = ContractPhaseProcessor(mapper)
}

// Main function, that wires up the application context deriving bean definitions
//  from the given class MyConfiguration, annotated with @Configuration
fun main() {
   AnnotationConfigApplicationContext(MyConfiguration::class.java).use { context ->
        val component = context.getBean(ContractPhaseProcessor::class.java)
        println(component)
        println(component.createResponse(listOf()))
    }
}

我希望这可以帮助您解决问题！