Category: Proxy usage

In Java, you can use the synchronized keyword to create a critical section in which one thread has exclusive access to a Java object. In JNI, you can use the MonitorEnter() and MonitorExit() functions for the same purpose. While we can't give you the synchronized keyword in C++, we can do something that is almost as good.

The runtime library provides you with the xmog_lock_holder utility type for the purpose of providing synchronization on a Java object. Here's how you might use it in your code:

MyProxyType       mpt = MyProxyType::getInstance();
 
// this is the scope to which the synchronization applies
{
    // the constructor attempts to grab the lock on the
    // passed in object, blocking if held by another thread
    xmog_lock_holder   monitor( mpt );
 
    ...
} // the 'monitor' object goes out of scope and 
  // its destructor releases the lock

You can synchronize on a type, i.e. the static members of a Java class, by using the xmog_java_class instance associated with a proxy type as illustrated in the following snippet:

xmog_java_class *      clazz = MyProxyType::get_class();
 
// this is the scope to which the synchronization applies
{
    // the constructor attempts to grab the lock on the
    // passed in object, in this case, a type object
    xmog_lock_holder   monitor( *clazz );
 
    ...
} // the 'monitor' object goes out of scope and 
  // its destructor releases the lock