OVERVIEW
As ISAM is defined for native code (primarily C), a bridge is
necessary to connect Java to the native code. This bridge is done through
JNI (Java Native Interface), allowing Java code to access ISAM as if it were just another
Java API, while allowing the original native code ISAM to execute and access the original
ISAM data.
ISAMJ is in two parts: the Java side and the JNI native side. The
Java side remains the same regardless of platform. The same Java interfaces
and Java classes are accessed on any platform from Windows to Solaris. The
JNI piece is unique to each platform.
ISAMJ Java
The ISAMJ Java side has two interface layers, a low-level and
a high-level interface. The low-level interface closely matches the original ISAM
specification, including functions such as isaddindex and iserase. The high-level
interface more closely resembles existing Java API's, encapsulating the ISAM
function in a more object-oriented framework; classes such as ISAMFile extends File and
ISAMRecord which may be extended by user record classes. The low-level functionality is
encompassed within the ISAM and ISAMConstants classes.
The high-level functionality is encompassed within the ISAMFile, ISAMRecord,
ISAMKey, ISAMAudHead, ISAMDictInfo and ISAMConstants classes.
ISAMJ Native
The ISAMJ native side implements a JNI interface used by the
Java side and accesses a native code shared library which implements the ISAM
functionality. Java native code must be in shared library/shared object
form (.DLL in Windows). The ISAMJ native side accesses this shared library, passing
requests and data from the Java side to the native ISAM driver. The native ISAM drivers
tested include D-ISAM and ObjecTrieve; of these two,
only D-ISAM provides variable length as well as fixed length functionality.
ISAMJ Deliverables
ISAMJ includes the high- and low-level functionality .class
files (Java executables). ISAMJ also includes the native isamj.dll or libisamj.so
connector piece. This connector piece is unique to each platform, currently
available for Windows and Solaris; other platforms are available upon request.
ISAMJ does not include ISAM functionality itself; this must
be provided by a third-party (such as Byte Designs D-ISAM). File created and accessed
using ISAMJ may be created and accessed using Java programs, while
the data is in the original binary datafile format.
ISAMJ includes the JavaDoc documentation of the classes, the format most used for Java
class documentation and most familiar to Java programmers.
Installation
Installation for development consists of unzipping or
untarring the distribution file. A Java file called 'isamj.jar' and several directories
will be created upon extracting the distribution file. The directories will include one
named 'docs' and one named after the platform (e.g., 'win32').
In the docs directory are the documentation files in JavaDoc .html format. They may be
viewed using any modern browser and are for the development machine only.
The isamj.jar file contains the Java .class files necessary
for the implementation and access of ISAMJ from Java. This isamj.jar file must be made
accessible to the Java Virtual Machine used in development (and later, the JVM used in
deployment). This may be done by adding it to the CLASSPATH, as in:
CLASSPATH=$CLASSPATH:{isamj-directory}/isamj.jar
export CLASSPATH
Or it may be done by copying it to the ext (extensions)
directory of Java. Or an IDE (Integrated Development Environment) may have its own method
of adding .jar files.
The native file (found in a directory named after the
platform, such as win32) will be named after isamj with the shared object extension for
the platform, such as isamj.dll, libisamj.so, libisamj.sa, or libisamj.sl. It must be
available in the same fashion that native shared object are always made available on the
native platform. In Windows, it will look in the PATH and current directory. On other
platforms, LD_LIBRARY_PATH must include the directory which contains the file.
Finally, the ISAM implementation itself (such as D-ISAM) must be present and available.
The ISAM implementation must be in the form of a shared library for it to be accessible by
Java. See the JavaDoc on ISAM for information on setting the filename. The native ISAM
library provides the actual ISAM functionality to which ISAMJ bridges. Follow the
directions for the ISAM implementation in regards to its setup.
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