Cpptasks - working hello world jni example on linux

Question

I have a working hello world example working on linux that uses cpptasks for the build. I'll post it here as I don't see any info on this out there. I hope this is helpful for you.
-Todd
Contents:
- build.xml
- helloworld.c
- helloWorldCWrapper.java
- directory structure
- environment vars
- output : $ant build
- output : $ant run
- References
build.xml
<?xml version="1.0" encoding="UTF-8"?>
<project basedir="." default="build" name="myJni">
     <property name="build" value="build"/>
     <property name="src" value="src"/>
     <property name="stub" location="stub"/>
     <property environment="os"/>
<!-- Load the cpptasks task -->
<taskdef resource="cpptasks.tasks"/>
<typedef resource="cpptasks.types"/>
     <path id="project.classpath">
<pathelement location="${build}"/>
<pathelement location="."/>
</path>
     <target name="init">
          <mkdir dir="${build}"/>
          <mkdir dir="${stub}"/>
</target>
<target name="clean" depends="init">      
          <delete>
               <fileset dir="${build}">
               <include name="*.class"/>
               </fileset>
               <fileset dir="${stub}">
               <include name="*.h"/>
               <include name="*.c"/>
               </fileset>
          </delete>
     </target>
<target name="jni-compile" description="--> create the jni h/c files">
     <javah class="com.bigdog.jni.helloWorldCWrapper" destdir="${stub}" verbose="yes" force="yes">
          <classpath refid="project.classpath"/>
     </javah>      
</target>
     <target name="build" depends="init, java-compile, jni-compile, c-compile">
</target>
     <target name="java-compile">
<echo message="${ant.project.name}: ${ant.file}"/>
<javac destdir="${build}">
<src path="${src}"/>
<classpath refid="project.classpath"/>
</javac>
     </target>
<target name="c-compile" description="--> compile c code">
<cc link="shared" outtype="shared" multithreaded="true" optimize="speed"
objdir="${build}" outfile="${build}/libhelloworld">
<compilerarg value="-Wall"/>
<compilerarg value="-D_JNI_IMPLEMENTATION_"/>
<compilerarg value="-fno-strict-aliasing"/>
<linker name="g++">
          <linkerarg value="-olibhelloworld.so"/>
     </linker>
<fileset dir="${src}" includes="helloworld.c"/>
     <includepath>
          <path path="${os.JAVA_HOME}/include"/>
          <path path="${os.JAVA_HOME}/include/linux"/>
          <path path="${basedir}/stub"/>
          <path path="${build}"/>
     </includepath>
</cc>
</target>
     <target name="run">
<echo message="${ant.project.name}: ${ant.file}"/>
          <echo message="java.library.path = ${java.library.path}"/>
          <echo message="LD_LIBRARY_PATH = ${os.LD_LIBRARY_PATH}"/>
<java classname="com.bigdog.jni.helloWorldCWrapper">
<classpath refid="project.classpath"/>
</java>
     </target>
</project>
helloworld.c
#include <jni.h>
#include <stdio.h>
#include "com_bigdog_jni_helloWorldCWrapper.h"
JNIEXPORT void JNICALL
Java_com_bigdog_jni_helloWorldCWrapper_print(JNIEnv *env, jobject obj)
          printf("Hello world :o)\n");
          return;
helloWorldCWrapper.java
package com.bigdog.jni;
public class helloWorldCWrapper {
     private native void print();
     public static void main(String[] args) {
          new helloWorldCWrapper().print();               
     static {
          System.loadLibrary("helloworld");
directory structure
./.project
./.classpath
./build
./build/com
./build/com/bigdog
./build/com/bigdog/jni
./build/com/bigdog/jni/helloWorldCWrapper.class
./build/history.xml
./build/helloworld.o
./build/libhelloworld.so
./build/dependencies.xml
./stub
./stub/com_bigdog_jni_helloWorldCWrapper.h
./src
./src/com
./src/com/bigdog
./src/com/bigdog/jni
./src/com/bigdog/jni/helloWorldCWrapper.java
./src/helloworld.c
./bin
./bin/helloworld.c
./build.xml
./build-user.xml
./history.xml
environment vars
user@machine:~/working/eclipse_proj/myJini$ export | grep LD
declare -x LD_LIBRARY_PATH="/home/user/working/eclipse_proj/myJini/build"...
Note: I had to modify the LD_LIBRARY_PATH in my .bashrc file. Modifying
it from the command line seemed to have no effect.
output : $ant build
Buildfile: /home/user/working/eclipse_proj/myJini/build.xml
init:
java-compile:
[echo] myJni: /home/user/working/eclipse_proj/myJini/build.xml
[javac] Compiling 1 source file to /home/user/working/eclipse_proj/myJini/build
jni-compile:
[javah] [Search path = /home/user/bin/jdk1.5.0_03/jre/lib/rt.jar:/home/user/bin/jdk1.5.0_03/jre/lib/i18n.jar:/home/user/bin/jdk1.5.0_03/jre/lib/sunrsasign.jar:/home/user/bin/jdk1.5.0_03/jre/lib/jsse.jar:/home/user/bin/jdk1.5.0_03/jre/lib/jce.jar:/home/user/bin/jdk1.5.0_03/jre/lib/charsets.jar:/home/user/bin/jdk1.5.0_03/jre/classes:/home/user/working/eclipse_proj/myJini/build:/home/user/working/eclipse_proj/myJini]
[javah] [Loaded /home/user/working/eclipse_proj/myJini/build/com/bigdog/jni/helloWorldCWrapper.class]
[javah] [Loaded /home/user/bin/jdk1.5.0_03/jre/lib/rt.jar(java/lang/Object.class)]
[javah] [Forcefully writing file /home/user/working/eclipse_proj/myJini/stub/com_bigdog_jni_helloWorldCWrapper.h]
c-compile:
[cc] Starting dependency analysis for 1 files.
[cc] 0 files are up to date.
[cc] 1 files to be recompiled from dependency analysis.
[cc] 1 total files to be compiled.
[cc] Starting link
build:
BUILD SUCCESSFUL
Total time: 2 seconds
output : $ant run
Buildfile: /home/user/working/eclipse_proj/myJini/build.xml
run:
[echo] myJni: /home/user/working/eclipse_proj/myJini/build.xml
[echo] java.library.path = /home/user/bin/jdk1.5.0_03/jre/lib/i386/server:/home/user/bin/jdk1.5.0_03/jre/lib/i386:/home/user/bin/jdk1.5.0_03/jre/../lib/i386:/home/user/working/eclipse_proj/myJini/build:/usr/local/qt/lib:/usr/local/qt/lib:/usr/local/qt/lib:/usr/local/qt/lib:/mnt/bea/p4/src910_150/bea/weblogic90/server/native/linux/i686:/lib:/lib/i686:/usr/lib:/usr/openwin/lib
[echo] LD_LIBRARY_PATH = /home/user/bin/jdk1.5.0_03/jre/lib/i386/server:/home/user/bin/jdk1.5.0_03/jre/lib/i386:/home/user/bin/jdk1.5.0_03/jre/../lib/i386:/home/user/working/eclipse_proj/myJini/build:/usr/local/qt/lib:/usr/local/qt/lib:/usr/local/qt/lib:/usr/local/qt/lib:/mnt/bea/p4/src910_150/bea/weblogic90/server/native/linux/i686:/lib:/lib/i686:/usr/lib:/usr/openwin/lib
Hello world :o)
BUILD SUCCESSFUL
Total time: 1 second
References:
http://public.cabit.wpcarey.asu.edu/janjua/java/jni/
http://bleaklow.com/blog/archive/000162.html
http://sourceforge.net/projects/ant-contrib
http://sourceforge.net/project/showfiles.php?group_id=36177&package_id=28636

Answer 1

VC++ works just fine.
I use the IDE rather than command-line processing. I create a "dll" project, and implement the functions defined by running javah.