Spring Boot 1.5.9与2.0.2私有实现Bean注入差异原因及修复方案

当Spring尝试装配一个拥有public接口和private实现类的Bean时，Spring Boot 2.0.2会抛出非法访问异常，具体栈跟踪如下：

Caused by: java.lang.IllegalAccessException: Class kotlin.reflect.jvm.internal.FunctionCaller$Constructor can not access a member of class com.example.demo.MyCompImpl with modifiers "public"
	at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:102) ~[na:1.8.0_112]
	at java.lang.reflect.AccessibleObject.slowCheckMemberAccess(AccessibleObject.java:296) ~[na:1.8.0_112]
	at java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:288) ~[na:1.8.0_112]
	at java.lang.reflect.Constructor.newInstance(Constructor.java:413) ~[na:1.8.0_112]
	at kotlin.reflect.jvm.internal.FunctionCaller$Constructor.call(FunctionCaller.kt:66) ~[kotlin-reflect-1.2.41.jar:1.2.41-release-74 (1.2.41)]
	at kotlin.reflect.jvm.internal.KCallableImpl.call(KCallableImpl.kt:107) ~[kotlin-reflect-1.2.41.jar:1.2.41-release-74 (1.2.41)]
	... 22 common frames omitted

版本差异对比 #

• Spring Boot 1.5.9：该场景下Bean装配流程正常，无任何异常抛出
• Spring Boot 2.0.2：触发IllegalAccessException，无法完成私有实现类的Bean初始化与装配

问题复现代码示例 #

package com.example.demo

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.builder.SpringApplicationBuilder
import org.springframework.stereotype.Component

@SpringBootApplication
class DemoApplication

fun main(args: Array<String>) {
    SpringApplicationBuilder(DemoApplication::class.java).run(*args)
}

interface ValueProvider {
    fun provideValue(): Double
}

@Component
private class ValueProviderImpl(): ValueProvider {
    override fun provideValue() = 3.1415
}

interface MyComp {
    fun getValue(): Double
}

@Component
private class MyCompImpl(val provider: ValueProvider): MyComp {
    override fun getValue() = provider.provideValue()
}

内容的提问来源于stack exchange，提问作者ohwhy