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.{{cite web
|last1=McMillan |first1=Robert
|date=1997-07-01 |df=mdy
|url=https://www.infoworld.com/article/2076977/microsoft-s-j-direct-called-death-of-java.html
|title=Microsoft's J/Direct called death of Java
|publisher=JavaWorld
|accessdate=2020-07-16
}}
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.{{cite web
|date=1997-08-01
|url=http://www.xent.com/FoRK-archive/july97/0491.html
|title=JFC; Microsoft declares war
|publisher=xent.com
|accessdate=2007-07-14
}}
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the drop by Microsoft of their specific Java virtual machine, and the switch to the .NET environment, J/Direct was no longer maintained.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
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:{{cite web
|url=http://msdn.microsoft.com/en-us/library/aa233951%28v=VS.60%29.aspx
|title=Aliasing (Method Renaming)
|publisher=Microsoft
|accessdate=2010-11-20
}}
{{sxhl|2=java|1=
/** @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.{{cite web
|url=http://www.codeguru.com/java/tij/tij0193.shtml
|title=J/Direct
|date=March 2001
|publisher=codeguru.com
|accessdate=2010-11-20
}}
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.{{cite web
|url=http://msdn.microsoft.com/en-us/library/aa264867%28v=VS.60%29.aspx
|title=How the VM Chooses Between ANSI and Unicode
|publisher=Microsoft
|accessdate=2010-11-20
}}
See also
- Java Native Interface
- Java Native Access
- P/Invoke, the equivalent .NET API
References
{{Reflist|colwidth=30em}}
External links
- [https://docs.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-6.0/aa242534(v=vs.60) Writing Windows-Based Applications with J/Direct]
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