Java GUI 中的线程安全问题

Java GUI 中的线程安全问题

线程安全问题：

From：http://www.jguru.com/faq/view.jsp?EID=131370


Question - Please explain why Swing is not thread safe and AWT is.

Answer
Simple answer is - "that's the design choice the Swing team made". It is a well-known fact that writing thread safe API/library is more difficult and inefficient.

So to simplify the implementation of Swing library they chose it to be not thread safe. The argument being that most of the GUI related work happens in the callbacks from the GUI which happen on the single GUI thread anyways. Granted - for long running tasks the user will have to do more work if he/she wants to do multithreaded activity. Not making Swing thread safe allowed them to implement the Swing which covered a lot more ground (new controls, layouts, keyboard actions, layered pane etc) in a short amount of time.

It is not that bad though - Swing does provide a mechanism to deal with the issues of threading -

• javax.swing.SwingUtilities.invokeLater(Runnable ...);
• javax.swing.SwingUtilities.invokeAndWait(Runnable ...);
• javax.swing.JProgressBar class
• javax.swing.ProgressMonitor
• javax.swing.ProgressMonitorInputStream
• SwingWorker

For more explaination of why they made that decision please see the following URLs:

• http://java.sun.com/products/jfc/tsc/articles/threads/threads1.html
• http://java.sun.com/products/jfc/tsc/articles/threads/threads2.html
• http://java.sun.com/products/jfc/tsc/articles/threads/threads3.html

The AWT is based on the OS's WIndowing System's peer objects which are inherently thread safe. That is why AWT is thread safe.

One can argue though that they should have provided factory methods (similar to collections framework) or subclasses to get thread safe versions of the Swing classes - for example, TSJTextField or TSJTree where the "TS" stands for 'thread safe'


另外 , swt和swing一样都是线程不安全的， 但是java.util.Timer确是安全的，

thread safe问题归根结底是该类和方法是否可重入，re-entrance.