Copyright 1998, O'Reilly & Associates, Inc. This package may be copied under the same terms as Perl itself. Disclaimers ----------- This is a work in progress, and relies on bleeding-edge technology from the network. Don't expect not to be surprised occasionally. Requirements ------------ Under Solaris and Linux (and other Unix-like systems), Perl 5.005 (or later) must be compiled and installed as a shared library (libperl.so). I had to use the system's malloc. JPL was originally built and tested with 5.004_04 and early Java 1.1 development kits. This version has not been well tested under other versions, so you can expect some rough edges. You need JDK 1.1. On Solaris, 1.1.5 has been verified to work. Linux users can try the latest version (1.1.3 or later) available from (for example): ftp://ftp.blackdown.org/pub/Linux/JDK/1.1.3/updates/libjava-1.1.3v2-1.tar.gz The get_jdk directory contains a script that will download JDK (but not the patch file above) off of the net for you. (This presumes you've already installed the modules mentioned in ../README.) You may need to ensure that all files under the ../jpl directory are writable. install-jpl expects to be run with super-user privileges so that it can put things in the right places. Microsoft Windows ----------------- Only a subset of JPL works under Microsoft Windows. This subset includes the JNI extension and the JPL module. This is enough for you to embed Java in Perl, but not Perl in Java. This has only been tested with the Sun JDK 1.1.8. I haven't tested it with JDK 1.2 (aka Java 2) or any Microsoft implementation of Java. Kaffe ----- You might notice some mention of Kaffe (www.kaffe.org) in the source files. This is because some preliminary work is being done in this area, but JPL doesn't yet work with Kaffe. What the heck is JPL? --------------------- JPL is a hybrid (to use the polite term) language. It's basically Java in which the methods can optionally be implemented by Perl code. A preprocessor called "JPL::Compile" looks at your .jpl file and spits out the appropriate .java, .c, .h, .pl, and .so files to accomplish the desired task. Hopefully a lot of those files can go away in the future as jpl mutates into a Perl-to-Java compiler. The long-term goal is for jpl to be able to take a pure Perl file and spit out a java .class file. This initial version of JPL is an attempt to begin to mesh the semantics of Java and Perl. Some people may find it useful in its current form, but you should know right up front that we've still got a ways to go with it. A journey of a thousand miles continues with the second step... JPL Syntax ---------- JPL syntax is trivial, given that you know Java and Perl. Pretend like you're writing a native Java method, but say "perl" instead of "native", and then instead of omitting the body of the method, put your Perl code in double curlies. (See Sample.jpl for an example.) Calling back from Perl to Java is done through the JNI (Java Native Interface). No weird transmogrifications are done by the preprocessor to your Perl code--it's all normal Perl. The preprocessor just wraps it up into funny subroutines you don't see unless you peek at the .pl file it generates. Installation ------------ There are two ways to install JPL. The first way gives you the ability to embed Perl in Java programs. You can also call back into Java from your embedded Perl programs. This should work well with most JDKs, and is the only option for people using a JDK that uses green threads (see your JDK documentation). The second way lets you embed Java in Perl, but doesn't provide support for the other direction. This is good, in theory, if you need to work with a lot of Java classes from within Perl. I say "in theory," because this doesn't actually work a lot of the time. To use this second way, you must be using a JDK with native threads. At this point, the second way is the only way to use JPL under Microsoft Windows. Oddly enough, this is the only platform under which the second way works! Installation the First Way (All of JPL) --------------------------------------- Run "install-jpl". You have to tell it whether you want to use the current directory for JPL_HOME or some other directory. Everything else should take care of itself, except that after install-jpl writes the setvars program, you are responsible to invoke it properly before any JPL applications can be compiled under the current shell. sh: eval `setvars -sh` csh: eval `setvars -csh` perl: eval `setvars -perl`; install-jpl has been tested under: Solaris 2.5.1 SPARC, GCC 2.8.0, Perl 5.005_03, JDK 1.1.7 Debian 2.1 x86, Perl 5.005_60, JDK 1.1.7v3 ******************** Solaris 2.5.1 Users: ******************** NOTE: Under Solaris 2.5.1, you may get an error message when install-jpl builds Sample.jpl: You must install a Solaris patch to run this version of the Java runtime. Please see the README and release notes for more information. Exiting. This is apparently a spurious message, and it has been reported to Sun. Although this message aborts the installation, all of JPL is installed by the time this message is reached. To recover and continue, run setvars as described above, cd to the Sample directory, and type 'make' to continue building. You can then run 'java Sample' to test the example. Unfortunately, each time you use 'make' to build a JPL application, it will abort when it tries to run 'perl -c' on the generated .pl file. However, you can continue building by typing 'make' again. Just-JNI (call into Java from Perl only) ---------------------------------------- This has been tested with: Debian 2.1 SPARC, Perl 5.005_60, JDK 1.2 beta (crashes with AWT, though) Windows NT 4.0 SP4, ActivePerl 519, JDK 1.1.8, Visual C++ Solaris 7, Perl 5.005_03, JDK 1.1.6, GCC 2.8.1 Solaris 7 Note (this probably applies to all native thread situations): Native threads were tricky. I had to build my own Perl, configured with: sh Configure -Dprefix=/opt/perl5.005 -Duseshrplib -Doptimize=-g \ -Uusemymalloc -D cc=gcc -Dusethreads -d When Configure let me edit config.sh, I changed libs to: libs='-lthread -lsocket -lnsl -ldl -lm -lposix4 -lpthread -lc -lcrypt' The leading -lthread is the only thing I had to add. How do I do this crazy thing? 1) Cd into the JPL directory. Type the following: perl Makefile.PL make make install Under windows, that's: perl Makefile.PL nmake nmake install 3) cd into the JNI directory (cd ../JNI or cd ..\JNI) 4) We now need to compile and make the Closer.class available to your JPL program. Closer is a WindowListener that closes the Frame we make in the test program. It seems that we've managed to fix the problem with CLASSPATH not getting propagated to the JVM, so if '.' is in your CLASSPATH, you should be able to compile Closer.java and leave it in the current directory: javac Closer.java 5) Make the demo: a) If you are on Windows, copy typemap.win32: copy typemap.win32 typemap (this step will probably go away when we clean up some of the WIN32 #defines) b) type the following: perl Makefile.PL make make test Under Windows: perl Makefile.PL nmake nmake test c) if all went well, type: make install or, under Windows: nmake install Mailing List ------------ To subscribe to the jpl mailing list, send an email message to jpl-subscribe@perl.org. CVS Access ---------- Information on accessing the bleeding edge JPL via CVS can be found at: http://users.ids.net/~bjepson/jpl/cvs.html More Info --------- You can look at the Sample and Test directories, as well as the ../eg directory for examples. Perhaps the most important bit of advice we can give you is to watch http://perl.oreilly.com for further information on how to get further information. Have the appropriate amount of fun.