Java SecurityManager checkAwtEventQueueAccess()用法及代碼示例

SecurityManager類checkAwtEventQueueAccess()方法

• checkAwtEventQueueAccess() 方法在 java.lang 包中可用。
• checkAwtEventQueueAccess() 方法用於通過使用 AWTPermission(“accessEventQueue”) 調用 checkPermission 來訪問 AWT(Abstract Window Toolkit) 事件隊列。
• checkAwtEventQueueAccess() 方法是一個非靜態方法，它隻能通過類對象訪問，如果我們嘗試使用類名訪問方法，那麽我們將得到一個錯誤。
• checkAwtEventQueueAccess() 方法可能在訪問 AWT 事件隊列時拋出異常。
  SecurityException- 當不允許調用線程訪問 AWT 事件隊列時，可能會拋出此異常。

用法:

    public void checkAwtEventQueueAccess();

參數：

• 它不接受任何參數。

返回值：

這個方法的返回類型是void，它什麽都不返回。

例：

// Java program to demonstrate the example 
// of void checkAwtEventQueueAccess()
// method of SecurityManager 

public class CheckAwtEventQueueAccess {
    public static void main(String[] args) {
        // By using setProperty() method is to set the policy property 
        // with security manager
        System.setProperty("java.security.policy", "file:/C:/java.policy");

        // Instantiating a SecurityManager object
        SecurityManager smgr = new SecurityManager();

        // By using setSecurityManager() method is to set the
        // security manager
        System.setSecurityManager(smgr);

        // By using CheckAwtEventQueueAccess() method is to check 
        // that awt event queue is accessed or not
        smgr.checkAwtEventQueueAccess();

        // Display the message when queue is acessible
        System.out.println("Not Restricted..");
    }
}

輸出

Exception in thread "main" java.security.AccessControlException:access denied (
java.awt.AWTPermission accessEventQueue)
        at java.security.AccessControlContext.checkPermission(AccessControlConte
xt.java:264)
        at java.security.AccessController.checkPermission(AccessController.java:
427)
        at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
        at java.lang.SecurityManager.checkAwtEventQueueAccess(SecurityManager.ja
va:1398)
        at CheckAwtEventQueueAccess.main(CheckAwtEventQueueAccess.java:18)