# Mirai Console Backend - JVM Plugins - Debug > 建议在 Java 9+ 的环境中进行排错, mirai-console 在 java 9+ 中的错误堆栈中报告了错误类来自哪个类加载器 ## 错误堆栈基本解析 ```log java.lang.Exception: Thread stack dump at java.base/java.lang.Thread.dumpStack(Thread.java) at example-plugin.mirai2.jar[shared]//com.example.exmapleplugin.sharedlib.SharedLib.handle(shared.kt:6) at example-plugin.mirai2.jar[private]//com.example.exmapleplugin.privatelib.PrivLib.cmd(priv.kt:5) at example-plugin.mirai2.jar//com.example.exmapleplugin.MyCommand.cmd(MyCommand.kt:63) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at ...... at net.mamoe.mirai.console.command.CommandManager.executeCommand$default(CommandManager.kt:125) at chat-command-0.5.1.jar//net.mamoe.mirai.console.plugins.chat.command.PluginMain.handleCommand(PluginMain.kt:86) at chat-command-0.5.1.jar//net.mamoe.mirai.console.plugins.chat.command.PluginMain$onEnable$2$1.invokeSuspend(PluginMain.kt:69) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at ...... ``` 来自 plugin 本身的类加载器的堆栈会以 插件文件名 开头, 其中 `...[private]` `....[shared]` 都是该插件使用的类库. - `[shared]` 代表是共享库, 其中的类可以被依赖此插件的其他插件解析到 - `[private]` 代表是私有库, 仅该插件自己内部使用, 依赖此插件的其他插件将不能解析到此类加载器的类 ## 多插件间数据交换结果和预期不符合 多插件间数据结果不一致 90% 是因为缺少依赖关系导致的未解析到相同的类导致结果不一致 关于如何建立关系, 见 [JVMPlugin - Data Exchange](./JVMPlugin-DataExchange.md) 可以使用以下代码确定是否是因为类链接错误导致的数据不一致 ```kotlin fun MiraiLogger.dumpClass(klass: Class<*>) { info { "Class name: $klass" } info { " |- loader: ${klass.classLoader}" } info { " |- module: ${klass.module}" } } ``` ```java public static void dumpClass(MiraiLogger logger, Class klass) { logger.info("Class name: " + klass); logger.info(" |- loader: " + klass.getClassLoader()); logger.info(" |- module: " + klass.getModule()); } ``` ## 使用的第三方库报错没有模块实现 在插件初始化的时候, 线程上下文类加载器依然还是 console 的系统类加载器 (`AppClassLoader`), 需要手动将其切换到插件的类加载器 详见 [Issue Comment](https://github.com/mamoe/mirai/issues/2138#issuecomment-1179673302) ```kotlin fun onEnable() { val oThreadCtxLoader = Thread.currentThread().contextClassLoader try { Thread.currentThread().contextClassLoader = javaClass.classLoader // ....... } finally { Thread.currentThread().contextClassLoader = oThreadCtxLoader } } ``` ## 使用依赖库后无法加载插件 / clinit 无法使用依赖库 错误类似 ```log 2023-12-08 00:23:42 E/main: Failed to init MiraiConsole. net.mamoe.mirai.console.internal.util.ServiceLoadException: Could not load service com.example.exmapleplugin.MyPlugin at .... Caused by: java.lang.NoClassDefFoundError: com/example/somelibrary/ClassFromLibrary at java.base/java.lang.Class.forName0(Native Method) at java.base/java.lang.Class.forName(Class.java:467) at net.mamoe.mirai.console.internal.util.PluginServiceHelper.loadService(PluginServiceHelper.kt:51) Caused by: java.lang.NoClassDefFoundError: org/quartz/SchedulerException ... 23 more Caused by: java.lang.ClassNotFoundException: com/example/somelibrary/ClassFromLibrary at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) Caused by: java.lang.ClassNotFoundException: com.example.somelibrary.ClassFromLibrary at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520) at net.mamoe.mirai.console.internal.plugin.JvmPluginClassLoaderN.loadClass(JvmPluginClassLoader.kt:389) ... 26 more ``` 此原因是因为 clinit 阶段时 mirai-console 还未加载依赖库至插件类搜索路径中。 如果您使用 mirai-console 2.16.0+ 请创建 `plugin.yml`, mirai-console 才能将依赖库在 clinit 阶段前加载到插件类搜索路径，见 [JVMPlugin - 通过资源文件提供静态信息](./JVMPlugin.md#%E9%80%9A%E8%BF%87%E8%B5%84%E6%BA%90%E6%96%87%E4%BB%B6%E6%8F%90%E4%BE%9B%E9%9D%99%E6%80%81%E4%BF%A1%E6%81%AF) 如果您使用 mirai-console 2.160 之前的版本, 请创建一个新的类，此类不要包含依赖库的代码，然后将此类的代码转移到您的真正的逻辑代码 示例 ```kotlin object OuterPlugin: KotlinPlugin(...) { override fun onEnable() { ActuallyPluginClassLoader.onEnable() } } object ActuallyPluginClassLoader { fun onEnable() { // ..... } } ``` > 底层分析 > > 为了实现插件之间的相互依赖，mirai-console 必须获取到插件的信息 (PluginDescription) 才能进行插件类路径链接操作 > > 在 mirai-console 2.16.0 之前，插件加载顺序为 > > - 加载插件主类 (即 clinit 阶段) > - 加载插件实例 (传递 PluginDescription 给 mirai-console) > - mirai-console 构建插件依赖关系，链接插件类路径 > - 执行插件的 onEnable > > 在 2.16.0+, 存在 plugin.yml 时, 插件加载的顺序为 > > - 加载 plugin.yml > - 构建插件依赖关系，链接插件类路径 > - 加载插件主类 > - 加载插件实例 > - 执行 onEnable ## java.lang.LinkageError: loader constraint violation ```log java.lang.LinkageError: loader constraint violation: when resolving method 'void io.ktor.client.request.HttpRequestBuilder.setMethod(io.ktor.http.HttpMethod)' the class loader 'test-ktor-dev.mirai2.jar' @61dde151 of the current class, com/kasukusakura/testktor/TestKtor$getTailrec$$inlined$get$2, and the class loader 'app' for the method's defining class, io/ktor/client/request/HttpRequestBuilder, have different Class objects for the type io/ktor/http/HttpMethod used in the signature (com/kasukusakura/testktor/TestKtor$getTailrec$$inlined$get$2 is in unnamed module of loader 'test-ktor-dev.mirai2.jar' @61dde151, parent loader 'global-shared' @32b9bd12; io.ktor.client.request.HttpRequestBuilder is in unnamed module of loader 'app') at ................. java.lang.LinkageError: loader constraint violation: when resolving method 'void io.ktor.client.request.HttpRequestBuilder.setMethod(io.ktor.http.HttpMethod)' the class loader 'test-ktor-dev.mirai2.jar' @61dde151 of the current class, com/kasukusakura/testktor/TestKtor$getTailrec$$inlined$get$2, and the class loader 'app' for the method's defining class, io/ktor/client/request/HttpRequestBuilder, have different Class objects for the type io/ktor/http/HttpMethod used in the signature ( com/kasukusakura/testktor/TestKtor$getTailrec$$inlined$get$2 is in unnamed module of loader 'test-ktor-dev.mirai2.jar' @61dde151, parent loader 'global-shared' @32b9bd12; io.ktor.client.request.HttpRequestBuilder is in unnamed module of loader 'app' ) ``` 翻译 ```log JVM 无法解析 com/kasukusakura/testktor/TestKtor$getTailrec$$inlined$get$2 中的方法引用 'void io.ktor.client.request.HttpRequestBuilder.setMethod(io.ktor.http.HttpMethod)' 搜索到的 'io.ktor.client.request.HttpRequestBuilder' 位于系统类加载器 'app' 中 HttpRequestBuilder 中的 HttpMethod 引用和 TestKtor$getTailrec$$inlined$get$2 得到的 HttpMethod 引用 不一致, 无法连接 ``` 结论: 插件没有附带完整的 ktor 依赖导致部分类解析至插件库加载器, 部分类解析至系统类加载器