new JFileChooser()遭遇AssertionError的解决方案

背景说明

今天在运行自己早前写的一个Swing应用程序时，在一个打开文件对话框的功能莫名其妙的遭遇java.lang.RuntimeException: java.lang.AssertionError。这是个断言错误，以前没有遇到过，一时搞不清楚状态。

具体报错信息如下，在语句new JFileChooser()出触发：

java.lang.RuntimeException: java.lang.AssertionError at java.beans.EventHandler.invokeInternal(EventHandler.java:489) at java.beans.EventHandler.access$000(EventHandler.java:279) at java.beans.EventHandler$1.run(EventHandler.java:430) at java.security.AccessController.doPrivileged(Native Method) at java.beans.EventHandler.invoke(EventHandler.java:428) at com.sun.proxy.$Proxy0.actionPerformed(Unknown Source) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.AbstractButton.doClick(AbstractButton.java:376) at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:833) at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:877) at java.awt.Component.processMouseEvent(Component.java:6525) at javax.swing.JComponent.processMouseEvent(JComponent.java:3321) at java.awt.Component.processEvent(Component.java:6290) at java.awt.Container.processEvent(Container.java:2234) at java.awt.Component.dispatchEventImpl(Component.java:4881) at java.awt.Container.dispatchEventImpl(Container.java:2292) at java.awt.Component.dispatchEvent(Component.java:4703) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462) at java.awt.Container.dispatchEventImpl(Container.java:2278) at java.awt.Window.dispatchEventImpl(Window.java:2739) at java.awt.Component.dispatchEvent(Component.java:4703) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746) at java.awt.EventQueue.access$400(EventQueue.java:97) at java.awt.EventQueue$3.run(EventQueue.java:697) at java.awt.EventQueue$3.run(EventQueue.java:691) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86) at java.awt.EventQueue$4.run(EventQueue.java:719) at java.awt.EventQueue$4.run(EventQueue.java:717) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75) at java.awt.EventQueue.dispatchEvent(EventQueue.java:716) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82) Caused by: java.lang.AssertionError at sun.awt.shell.Win32ShellFolder2$4.call(Win32ShellFolder2.java:400) at sun.awt.shell.Win32ShellFolder2$4.call(Win32ShellFolder2.java:398) at sun.awt.shell.Win32ShellFolderManager2$ComInvoker.invoke(Win32ShellFolderManager2.java:535) at sun.awt.shell.ShellFolder.invoke(ShellFolder.java:518) at sun.awt.shell.Win32ShellFolder2.getIShellFolder(Win32ShellFolder2.java:398) at sun.awt.shell.Win32ShellFolder2.access$200(Win32ShellFolder2.java:72) at sun.awt.shell.Win32ShellFolder2$2.call(Win32ShellFolder2.java:298) at sun.awt.shell.Win32ShellFolder2$2.call(Win32ShellFolder2.java:296) at sun.awt.shell.Win32ShellFolderManager2$ComInvoker.invoke(Win32ShellFolderManager2.java:535) at sun.awt.shell.ShellFolder.invoke(ShellFolder.java:518) at sun.awt.shell.Win32ShellFolder2.<init>(Win32ShellFolder2.java:296) at sun.awt.shell.Win32ShellFolderManager2.createShellFolderFromRelativePIDL(Win32ShellFolderManager2.java:95) at sun.awt.shell.Win32ShellFolder2$11.call(Win32ShellFolder2.java:819) at sun.awt.shell.Win32ShellFolder2$11.call(Win32ShellFolder2.java:807) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at sun.awt.shell.Win32ShellFolderManager2$ComInvoker$3.run(Win32ShellFolderManager2.java:511) at java.lang.Thread.run(Thread.java:745)

解决方案(也就是问题原因)

经过在Bing上面的搜索，找到相关英文资料(百度上面没有查找到相关信息)。

最后的解决方案是：禁用JVM的-esa参数设置(Disable assertions by removing -esa virtual machine argument.)

-enableassertions[:<package name>"..." | :<class name> ]
-ea[:<package name>"..." | :<class name> ]
上述参数就用来设置JVM是否启动断言机制（从JDK1.4开始支持），缺省时JVM关闭断言机制。用-ea可打开断言机制，不加<packagename>和classname时运行所有包和类中的断言，如果希望只运行某些包或类中的断言，可将包名或类名加到-ea之后。例如要启动包com.wombat.fruitbat中的断言，可用命令java -ea:com.wombat.fruitbat...<Main Class>。

-enablesystemassertions
-esa
激活系统类的断言。

然后我就回到Netbeans中查看该工程的运行参数，还真设置了-ea -esa，但是我完全不知道是什么时候设置上的，肯定不是我自己设置的。移除掉VM选项中的内容即可正常运行了。