J/Direct

J/Direct was a technology included in some versions of Microsoft's 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the drop by Microsoft of their specific Java Virtual Machine, and the switch to the .NET environment, J/Direct was no longer maintained.

Contents

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[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

References

  1. ^ "Microsoft's J/Direct called death of Java". JavaWorld. 1997-07-01. http://www.javaworld.com/javaworld/jw-07-1997/jw-07-jdirect.html?page=1. Retrieved 2010-11-20. 
  2. ^ "JFC; Microsoft declares war". xent.com. 1997-08-01. http://www.xent.com/FoRK-archive/july97/0491.html. Retrieved 2007-07-14. 
  3. ^ "Aliasing (Method Renaming)". Microsoft. http://msdn.microsoft.com/en-us/library/aa233951%28v=VS.60%29.aspx. Retrieved 2010-11-20. 
  4. ^ "J/Direct". codeguru.com. http://www.codeguru.com/java/tij/tij0193.shtml. Retrieved 2010-11-20. 
  5. ^ "How the VM Chooses Between ANSI and Unicode". Microsoft. http://msdn.microsoft.com/en-us/library/aa264867%28v=VS.60%29.aspx. Retrieved 2010-11-20. 

External links