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HDF Newsletter 42
May 26, 1999
CONTENTS
Release of Java Products v2.3
A new release of the HDF Java Products is now available from:
http://hdf.ncsa.uiuc.edu/java-hdf-html/download.html
This release includes many fixes and performance enhancements
to the Java HDF Viewer and Java HDF Interface. This release
also includes a complete implementation of the Java HDF Server,
which supports transparent access to remote HDF files. The
release includes pre-built binaries (including the HDF library)
for several popular platforms, and full source code.
For complete information, see:
http://hdf.ncsa.uiuc.edu/java-hdf-html/
Below is a list of new features in release 2.3 of the JHV.
For a complete list of features, see the JHV User's Guide.
(http://hdf.ncsa.uiuc.edu/java-hdf-html/jhv/index.html)
- Distributed with the newest released HDF library, HDF41r3.
- Significant performance improvement to handle larger datasets.
- Zoom in and out to navigate large images.
- All new and improved "spreadsheet" package.
- Transparent access to remote files with RMI server, servlet,
or standalone server.
- Ability to modify and save spreadsheet data.
- A User Preferences Menu.
- Both 'bounding-box' and entry form selection of a subset of
an SDS array or raster image.
- Field and record selections in the Vdata spreadsheet.
- Revised and updated Online User's Guide.
The Java HDF products provide Java classes for reading and creating HDF
files. These classes are designed to operate as a "data server" for HDF,
accepting requests (Java objects describing what to read) and returning
data and metadata from an HDF file (as Java objects). The Java HDF Viewer
uses these classes to access HDF files on local disk.
Starting with Release 2.3, the Java HDF Products also include classes to
transparently access HDF files across a network. The HDF Java Products can
be run as a server on any system that wishes to share the contents of HDF
files with JHV clients across a network. The Java HDF Server contains
exactly the same code as used in the Java HDF Viewer client, with
additional code to send the request to a remote system and return the
results as serialized Java objects via a network. Release
2.3 of the JHV contains the complete code for both the client and
server.
To access data on a remote system, the JHS must be installed and started.
The Java HDF server can be configured in three different ways:
- A standalone server
The server runs as a standalone program which listens on a socket.
- A Servlet
The server runs as a Servlet, plugged in to a Java Web server.
- An RMI Remote Object
The server is accessed as a Java object using the Java Remote
Invocation Method (RMI).
A JHV client can use none, any, or all of these methods to access HDF
files on remote systems, depending on how the remote system's Java HDF
Server is configured. In each case, the server functions identically,
and the results returned are the same from each, and for files on local
disk. The features and display are identical no matter where the HDF
file is located.
For more complete information about the Java HDF Server, see:
http://hdf.ncsa.uiuc.edu/java-hdf-html/jhs/index.html
GR interface supports JPEG compression
Newsletter 41, announcing the release of HDF 4.1r3, failed to mention
that the GR interface now supports JPEG compression. Using C, you
can now use GRsetcompress to compress a GR image with JPEG compression.
However, the Fortran counterpart to this function (mgscompress) does not
support JPEG compression. We will be providing a new GR Fortran function
that supports JPEG compression in the near future.