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Getting Started

This section describes some tips and hints on how to get the interface started. This is actually where most problems occur.

Windows

Under Windows, you should add SICStus Prolog's and Java's DLL directories to your %PATH%. This will enable Windows library search method to locate all relevant DLLs. For SICStus, this is the same as where sicstus.exe is located, usually C:\Program Files\SICStus Prolog 3.9.1\bin. For Java, it is usually C:\jdk1.3.1\jre\bin\hotspot (for JDK 1.2.2 it would be C:\jdk1.2.2\jre\bin\classic).

For example (Windows NT/2000/XP): 

set PATH=C:\jdk1.3.1\jre\bin\hotspot;%PATH%
set PATH=C:\Program Files\SICStus Prolog 3.9.1\bin;%PATH%

UNIX

When library(jasper) is used to embed Java in a SICStus development system or run-time system, then the run-time linker needs to be told where to find the Java libraries (e.g. libjvm.so). During installation, InstallSICStus will build either the sicstus executable or the jasper foreign resource so that it contains the necessary information; the detail are platform dependent.

If you use spld to relink SICStus or to build a run-time system, you can use the command line option --resource=-jasper (note the minus sign). This tells spld to include the search path (rpath) in the executable needed to ensure that library(jasper) can find the Java libraries.

If you want to run sicstus with another Java than what was specified during installation, you can use spld without the --resources option to get a SICStus executable without any embedded Java paths. In this case, you need to set the environment variable LD_LIBRARY_PATH (or similar) appropriately. One example of this is to use the JDK 1.3 server version instead of the default (client) version.

Alternatively, you can use spld with the --resource=-jasper and --with-jdk=DIR options to generate a development system with embedded paths to another Java directory tree. This will only work if the alternative directory tree has the same structure as the JDK directory seen by InstallSICStus.

Running Java from SICStus

If SICStus is used as parent application, things are usually really simple. Just execute the query | ?- use_module(library(jasper)).. After that, it is possible to perform meta-calls as described in Jasper Library Predicates.

On UNIX, you may encounter the following error message: 

% sicstus
SICStus 3.8 (sparc-solaris-5.5.1): Wed Sep 22 08:42:14 MET DST 1999
Licensed to SICS
| ?- use_module(library(jasper)).
[...]
{SYSTEM ERROR: 'Attempted to load Java engine into sbrk\'d
SICStus system (try starting SICStus with -m option)'}
[...]

Since most platforms don't allow sbrk() and malloc() (or threads) to coexist peacefully, SICStus refuses to load the JVM if not the -m flag was given to SICStus. The message can, as the error message suggests, be avoided if SICStus is started with the -m flag: 

% sicstus -m
The -m flag is not needed, and is ignored, on Windows.

When Jasper is used in run-time systems, additional constraints apply as described in Runtime Systems on Target Machines. The Java to SICStus interface relies on dynamically loading the SICStus run-time system. For this reason, it is not possible to use library(jasper) from an executable that links statically with the SICStus run-time.

Running SICStus from Java

If Java is used as parent application, things are a little more complicated. There are a couple of things which need to be taken care of. The first is to specify the correct class path so that Java can find the Jasper classes (SICStus, SPTerm, and so on). This is done by specifying the pathname of the file jasper.jar: 

% java -classpath $SP_PATH/bin/jasper.jar ...

SP_PATH does not need to be set; it is only used here as a placeholder. See the documentation of the Java implementation for more info on how to set classpaths.

The second is to specify where Java should find the Jasper native library (libspnative.so or spnative.dll), which the SICStus class loads into the JVM by invoking the method System.loadLibrary("spnative"). The loadLibrary method uses a platform dependent search method to locate the Jasper native library, and quite often this method fails. A typical example of such a failure looks like: 

% java -classpath [...]/jasper.jar se.sics.jasper.SICStus
Trying to load SICStus.
Exception in thread "main" java.lang.UnsatisfiedLinkError: no spnative
in java.library.path
	at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1133)
	at java.lang.Runtime.loadLibrary0(Runtime.java:470)
	at java.lang.System.loadLibrary(System.java:745)
	at se.sics.jasper.SICStus.loadNativeCode(SICStus.java:37)
	at se.sics.jasper.SICStus.initSICStus(SICStus.java:80)
	at se.sics.jasper.SICStus.<init>(SICStus.java:111)
	at se.sics.jasper.SICStus.main(SICStus.java:25)

On UNIX, this can be fixed by explicitly setting the Java property java.library.path to the location of libspnative.so, like this: 

% java -Djava.library.path=/usr/local/lib [...]

On Windows, Java must be able to find spnative.dll through the PATH environment variables and setting -Djava.library.path can lead to problems if multiple versions of SICStus has been installed.

If this works properly, SICStus should have been loaded into the JVM address space. The only thing left is to tell SICStus where the runtime library (i.e. sprt.sav) is located. On those platforms where the SICStus run-time system can determine its own location, e.g. Windows, Solaris and Linux, the run-time system will find the runtime library automatically. Otherwise, you may choose to specify this explicitly by either giving a second argument when initializing the SICStus object or by specifying the property sicstus.path:

Example (UNIX): 

% java -Dsicstus.path=/usr/local/lib/sicstus-3.9

If you do not specify any explicit path, SICStus will search for the runtime library itself.

If everything is set up correctly, you should be able to call main (which contains a short piece of test-code) in the SICStus root class, something like this: 

% java -Djava.library.path="/usr/local/lib" \
       -Dsicstus.path="/usr/local/lib/sicstus-3.9.1" \
       -classpath "/usr/local/lib/sicstus-3.9.1/bin/jasper.jar" \
        se.sics.jasper.SICStus
Trying to load SICStus.
If you see this message, you have successfully
initialized the SICStus Prolog engine.

On Windows, it would look something like this, depending on the shell used: 

% java -classpath "C:/Program Files/SICStus Prolog 3.9.1/bin/jasper.jar" se.sics.jasper.SICStus
Trying to load SICStus.
If you see this message, you have successfully
initialized the SICStus Prolog engine.

If more than one se.sics.jasper.SICStus instance will be created, then the SICStus run-times named e.g. libsprt39_instance_01_.so, need to be available as well. See Runtime Systems on Target Machines.