J/Direct
J/Direct was a technology included in some versions of Microsoft Java Virtual Machine, which allowed direct calls into the Windows API. J/Direct was specific of Microsoft's Virtual Machine, in replacement of the standard Java Native Interface (JNI).
A Java program which used J/Direct would not run on platforms other than Microsoft Windows.
The release of J/Direct (along with AFC and WFC), was part of an effort by Microsoft to gain leadership on the growing Java community.[1]
Since this destroyed one of the main advantages of Java, its cross-platform nature, J/Direct was often seen as an attempt by Microsoft to undermine Java's cross-platform capabilities, and an example of the tactic of embrace, extend and extinguish.[2]
After the drop by Microsoft of their specific Java virtual machine, and the switch to the .NET environment, J/Direct was no longer maintained.
Architecture
[edit]J/Direct used a kind of annotation in Java code to make the link between Java and Windows functions. As annotations did not exist in Java when J/Direct was designed, Microsoft used a special syntax in Java comments.
For example, to declare the GetSysColor function in the User32 API:[3]
/** @dll.import("USER32", entrypoint="GetSysColor") */
static native int getSysColor(int nIndex);
The Microsoft Java implementation already provided a pre-defined package which provided a set of pre-defined classes bound to the User32, Gdi32.dll, and Kernel32.dll APIs.[4]
Additionally, the Microsoft VM used some built-in rules to be able to bind automatically the Java code to some Windows API functions. For example, it chose automatically between ANSI and Unicode versions of Windows API functions.[5]
See also
[edit]- Java Native Interface
- Java Native Access
- P/Invoke, the equivalent .NET API
References
[edit]- ^ McMillan, Robert (July 1, 1997). "Microsoft's J/Direct called death of Java". JavaWorld. Retrieved 2020-07-16.
- ^ "JFC; Microsoft declares war". xent.com. 1997-08-01. Retrieved 2007-07-14.
- ^ "Aliasing (Method Renaming)". Microsoft. Retrieved 2010-11-20.
- ^ "J/Direct". codeguru.com. March 2001. Retrieved 2010-11-20.
- ^ "How the VM Chooses Between ANSI and Unicode". Microsoft. Retrieved 2010-11-20.
External links
[edit]
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