单元测试出错Native library for Attach API not available in this JRE

偶然一天，运行eclipse单元测试，报错：

java.lang.IllegalStateException: Native library for Attach API not available in this JRE
	at mockit.internal.startup.JDK6AgentLoader.getVirtualMachineImplementationFromEmbeddedOnes(JDK6AgentLoader.java:81)
	at mockit.internal.startup.JDK6AgentLoader.loadAgent(JDK6AgentLoader.java:54)
	at mockit.internal.startup.AgentInitialization.initializeAccordingToJDKVersion(AgentInitialization.java:21)
	at mockit.internal.startup.Startup.initializeIfNeeded(Startup.java:208)
java.lang.IllegalStateException: Native library for Attach API not available in this JRE
	at mockit.internal.startup.JDK6AgentLoader.getVirtualMachineImplementationFromEmbeddedOnes(JDK6AgentLoader.java:81)
	at mockit.internal.startup.JDK6AgentLoader.loadAgent(JDK6AgentLoader.java:54)
	at mockit.internal.startup.AgentInitialization.initializeAccordingToJDKVersion(AgentInitialization.java:21)
	at mockit.internal.startup.Startup.initializeIfNeeded(Startup.java:208)

检查了下，发现由于最近jmockit升级，导致eclipse的参数出了问题影响的。进入eclipse-->preference-->TestNG-->Run/Debug，这里有个设置运行时JVM args,把jmockit.jar设置下，格式为：-javaagent:D:\repository\com\alibaba\external\test.jmockit\0.999.11\test.jmockit-0.999.11.jar。

重新跑单元测试，运行正常！问题解决；

这个出错有点奇怪，通过出错类，进行跟踪，发现最后的出错信息如下：

 Class  JDK6AgentLoader{
private VirtualMachine attachToThisVM()
   {
      try {
         return VirtualMachine.attach(pid);
      }
      catch (AttachNotSupportedException e) {
         throw new RuntimeException(e);
      }
      catch (IOException e) {
         throw new RuntimeException(e);
      }
   }
 private VirtualMachine getVirtualMachineImplementationFromEmbeddedOnes()
   {
      try {
         if (File.separatorChar == '\\') {
            return new WindowsVirtualMachine(ATTACH_PROVIDER, pid);
         }
         else {
            return new LinuxVirtualMachine(ATTACH_PROVIDER, pid);
         }
      }
  catch (AttachNotSupportedException e) {
         throw new RuntimeException(e);
      }
      catch (IOException e) {
         throw new RuntimeException(e);
      }
      catch (UnsatisfiedLinkError e) {
         throw new IllegalStateException("Native library for Attach API not available in this JRE", e);
      }
}

通过文件路径判断是windwo，还是linux操作系统，从代码看catch并抛出异常的处理很常见；

WindowsVirtualMachine{ 
static
/*     */   {
/* 167 */     System.loadLibrary("attach");
/* 168 */     init();
/* 169 */     stub = generateStub();
/*     */   }
}

如果没有-javaagent,那么上面的代码就回出错，而这部分是虚拟机启动的装载初始化操作，所以javaagent设置的是虚拟机启动初始化类；

jmockit里面用到了jdk6.0的不少特性，jdk6.0的动态修改和装载还是挺强大的。