Exception Handling for System.exit(status)

Preface#

TopicCommand.main(args)
Encountered a problem when executing the command to create a topic in kafka using zookeeper. In the code of the open-source tool, when creating the topic, it eventually performs a System.exit(0) operation, which terminates our JVM. At this point, we cannot modify the code of the tool, so we can try to catch System.exit(status) from a different perspective.

Implementation#

Inherit from the SecurityManager class, which is from java.lang.
Then override the checkExit(int status) method.

static class DemoSecurityManager extends SecurityManager {  
	@Override public void checkExit(int status) {  
		throw new SecurityException();  
	}  
}

Add this code before the code block that will execute System.exit(status), and try-catch this code.

@Test  
void testMain() {  
  System.out.println("startMain");  
  DemoSecurityManager demoSecurityManager = new DemoSecurityManager();  
  System.setSecurityManager(demoSecurityManager);
  try {  
		main(new String[]{});
  } catch (Exception e) {  
		System.err.println("Skip the method that exits, and continue execution");
  }  
  System.out.println("endMain");
  // Prevent memory overflow
  System.setSecurityManager(null);
}  
  
public static void main(String[] args) {
  System.out.println("testMain");
  System.exit(0);  
}

This will result in the following execution result:

startMain
testMain
endMain