从JDK8升级至JDK17后JUnit测试因Mockito初始化失败报错

报错信息 #

java.lang.IllegalStateException: Could not initialize plugin: interface org.mockito.plugins.MockMaker (alternate: null)
at org.mockito.internal.configuration.plugins.PluginLoader$1.invoke(PluginLoader.java:84)
at jdk.proxy2/jdk.proxy2.$Proxy26.isTypeMockable(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
at org.mockito.internal.configuration.plugins.PluginInitializer.loadImpl(PluginInitializer.java:52)
... 59 more
Caused by: org.mockito.exceptions.base.MockitoInitializationException:
Could not initialize inline Byte Buddy mock maker.

It appears as if your JDK does not supply a working agent attachment mechanism.
Java : 17
JVM vendor name : Oracle Corporation
JVM vendor version : 17.0.11+7-LTS-207
JVM name : Java HotSpot(TM) 64-Bit Server VM
JVM version : 17.0.11+7-LTS-207
JVM info : mixed mode, sharing
OS name : Windows 10
OS version : 10.0
at org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker.(InlineByteBuddyMockMaker.java:234)
... 65 more
Caused by: java.lang.NoClassDefFoundError: net/bytebuddy/agent/ByteBuddyAgent
at org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker.(InlineByteBuddyMockMaker.java:117)
... 65 more
Caused by: java.lang.ClassNotFoundException: net.bytebuddy.agent.ByteBuddyAgent
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
... 66 more

核心原因 #

报错根源是缺少net.bytebuddy.agent.ByteBuddyAgent类，Mockito的内联Mock生成器依赖该类在JDK17环境中完成代理类创建。JDK17的模块系统与JDK8差异较大，旧版本Mockito未适配JDK17，导致依赖缺失。

解决步骤 #

• 升级Mockito版本：使用支持JDK17的Mockito版本（推荐4.0+，例如4.11.0及以上），新版本已适配JDK17模块系统，会自动引入兼容的ByteBuddy依赖。
• 手动补充ByteBuddy Agent依赖：若升级Mockito后问题仍存在，直接添加依赖：
  Maven：

  <dependency>
      <groupId>net.bytebuddy</groupId>
      <artifactId>byte-buddy-agent</artifactId>
      <version>1.14.11</version>
      <scope>test</scope>
  </dependency>
  

  Gradle：

  testImplementation 'net.bytebuddy:byte-buddy-agent:1.14.11'
  

• 临时切换Mock生成器（不推荐长期使用）：在src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker文件中添加：

  mock-maker-inline=false
  

  该方案会禁用内联生成器，使用传统Mock方式，仅作为临时应急手段，因为内联生成器支持更多Mock场景。

内容的提问来源于stack exchange，提问作者Shivangi Tripathi