Update readme

Author: stellaraccident

README.markdown

@@ -29,3 +29,43 @@ Syntax
 		--cflags			CFLAGS to use when compiling a JNI library
 		--ldflags			LDFLAGS to use when linking to the jvm
 		
+Example Usage
+-------------
+I wrote this tool primarily to aid in building JNI libraries.  All of the other options are present because they are easy to get at and I was forever writing little one liner java programs to pull them out of the system properties.
+
+Here is an example Linux makefile for building a shared library:
+
+	JAVA_CMD ?= java
+	CFLAGS ?= -O3
+	FREETYPE_CFLAGS ?= $(shell freetype-config --cflags)
+	JAVA_CFLAGS ?= $(shell $(JAVA_CMD) -jar java-config.jar --cflags)
+
+
+	libmapnik-jni.so: mapnikjni.cpp mapnikjni.h
+		g++ -o libmapnik-jni.so \
+			-fPIC -shared \
+			$(CFLAGS) \
+			$(FREETYPE_CFLAGS) \
+			$(JAVA_CFLAGS) \
+			mapnikjni.cpp \
+			$(LDFLAGS) \
+			-lmapnik2
+
+And here is an example OSX makefile for building a jnilib:
+	JAVA_CMD ?= java
+	CFLAGS ?= -O3
+	FREETYPE_CFLAGS ?= $(shell freetype-config --cflags)
+	JAVA_CFLAGS ?= $(shell $(JAVA_CMD) -jar java-config.jar --cflags)
+
+
+	libmapnik-jni.jnilib: mapnikjni.cpp mapnikjni.h
+		g++ -dynamiclib -o libmapnik-jni.jnilib \
+			$(CFLAGS) \
+			$(FREETYPE_CFLAGS) \
+			$(JAVA_CFLAGS) \
+			mapnikjni.cpp \
+			$(LDFLAGS) \
+			-lmapnik2 -framework JavaVM
+
+I used to use autoconf or other such craziness for this stuff, but JNI libraries are usually simple enough to require just quick incantations like the above.  Bundling the java-config.jar with your source and using it to discover compilation options on the fly makes it all self-configuring.
+