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我正在使用ByteBuddy重新綁定另一個庫的類以向其添加Spring依賴注入。問題是我不能實例化用作攔截器的類，這意味着我不能使用Spring將ApplicationContext注入攔截器。在運行時生成的類中使用Kotlin對象
要解決這個問題，我創建了一個對象StaticAppContext，其獲取實現ApplicationContextAware注入ApplicationContext：
@Component
object StaticAppContext : ApplicationContextAware {
private val LOGGER = getLogger(StaticAppContext::class)
@Volatile @JvmStatic lateinit var context: ApplicationContext
override fun setApplicationContext(applicationContext: ApplicationContext?) {
context = applicationContext!!
LOGGER.info("ApplicationContext injected")
}
}
是能否注入就好了（我可以看到日誌消息），但是當我嘗試從攔截器訪問ApplicationContext，我得到kotlin.UninitializedPropertyAccessException: lateinit property context has not been initialized。
是變基類和incerceptor在這個類中定義的類：
package nu.peg.discord.d4j
import net.bytebuddy.ByteBuddy
import net.bytebuddy.dynamic.ClassFileLocator
import net.bytebuddy.dynamic.loading.ClassLoadingStrategy
import net.bytebuddy.implementation.MethodDelegation
import net.bytebuddy.implementation.SuperMethodCall
import net.bytebuddy.implementation.bind.annotation.*
import net.bytebuddy.matcher.ElementMatchers
import net.bytebuddy.pool.TypePool
import nu.peg.discord.config.BeanNameRegistry.STATIC_APP_CONTEXT
import nu.peg.discord.config.StaticAppContext
import nu.peg.discord.util.getLogger
import org.springframework.beans.BeansException
import org.springframework.beans.factory.config.AutowireCapableBeanFactory
import org.springframework.context.annotation.DependsOn
import org.springframework.stereotype.Component
import sx.blah.discord.api.IDiscordClient
import sx.blah.discord.modules.Configuration
import sx.blah.discord.modules.IModule
import sx.blah.discord.modules.ModuleLoader
import java.lang.reflect.Constructor
import java.util.ArrayList
import javax.annotation.PostConstruct
/**
* TODO Short summary
*
* @author Joel Messerli @15.02.2017
*/
@Component @DependsOn(STATIC_APP_CONTEXT)
class D4JModuleLoaderReplacer : IModule {
companion object {
private val LOGGER = getLogger(D4JModuleLoaderReplacer::class)
}
@PostConstruct
fun replaceModuleLoader() {
val pool = TypePool.Default.ofClassPath()
ByteBuddy().rebase<Any>(
pool.describe("sx.blah.discord.modules.ModuleLoader").resolve(), ClassFileLocator.ForClassLoader.ofClassPath()
).constructor(
ElementMatchers.any()
).intercept(
SuperMethodCall.INSTANCE.andThen(MethodDelegation.to(pool.describe("nu.peg.discord.d4j.SpringInjectingModuleLoaderInterceptor").resolve()))
).make().load(ClassLoader.getSystemClassLoader(), ClassLoadingStrategy.Default.INJECTION)
LOGGER.info("The D4J ModuleLoader has been replaced with ByteBuddy to allow for Spring injection")
}
override fun getName() = "Spring Injecting Module Loader"
override fun enable(client: IDiscordClient?) = true
override fun getVersion() = "1.0.0"
override fun getMinimumDiscord4JVersion() = "1.7"
override fun getAuthor() = "Joel Messerli <[email protected]>"
override fun disable() {}
}
class SpringInjectingModuleLoaderInterceptor {
companion object {
private val LOGGER = getLogger(SpringInjectingModuleLoaderInterceptor::class)
@Suppress("UNCHECKED_CAST")
@JvmStatic
fun <T> intercept(
@This loader: ModuleLoader,
@Origin ctor: Constructor<T>,
@Argument(0) discordClient: IDiscordClient?,
@FieldValue("modules") modules: List<Class<out IModule>>,
@FieldValue("loadedModules") loadedModules: MutableList<IModule>
) {
LOGGER.debug("Intercepting $ctor")
val loaderClass = loader.javaClass
val clientField = loaderClass.getDeclaredField("client")
clientField.isAccessible = true
clientField.set(loader, discordClient)
val canModuleLoadMethod = loaderClass.getDeclaredMethod("canModuleLoad", IModule::class.java)
canModuleLoadMethod.isAccessible = true
val factory = StaticAppContext.context.autowireCapableBeanFactory
for (moduleClass in modules) {
try {
val wired = factory.autowire(moduleClass, AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE, false) as IModule
LOGGER.info("Loading autowired module {}@{} by {}", wired.name, wired.version, wired.author)
if (canModuleLoadMethod.invoke(loader, wired) as Boolean) {
loadedModules.add(wired)
} else {
LOGGER.info("${wired.name} needs at least version ${wired.minimumDiscord4JVersion} to be loaded (skipped)")
}
} catch (e: BeansException) {
LOGGER.info("Spring could not create bean", e)
}
}
if (Configuration.AUTOMATICALLY_ENABLE_MODULES) { // Handles module load order and loads the modules
val toLoad = ArrayList<IModule>(loadedModules)
val loadModuleMethod = loaderClass.getDeclaredMethod("loadModule", IModule::class.java)
while (toLoad.size > 0) {
toLoad.filter { loadModuleMethod.invoke(loader, it) as Boolean }.forEach { toLoad.remove(it) }
}
}
LOGGER.info("Module loading complete")
}
}
}
當我調試這個的IntelliJ顯示了創建StaticAppContext的新實例時，攔截試圖訪問StaticAppContext，這是有道理的，因爲拋出異常。
從生成的代碼調用時，Kotlin對象是不是真正的Singletons，或者我做錯了什麼？什麼是解決這個問題的方法？
該項目還可以在Github上找到：https://github.com/jmesserli/discord-bernbot/tree/master/src/main/kotlin/nu/peg/discord
編輯
我能夠通過移除spring-boot-devtools其中添加自己的ClassLoader來解決這個問題。當我嘗試使用Thread.currentThread().contextClassLoader的建議時，我得到了一個不同的例外情況，告訴我它已經加載了不同的ClassLoader（這證實這是ClassLoader的問題）。而且，似乎可能有種族的假設是正確的。
我現在有一個不同的問題，我會做一些研究，看看我能否自己解決它。