Java overview

About

In the GhostPDL repository sample Java projects can be found in /demos/java.

Within this location the following folders are of relevance:

• jni jni
• gsjava gsjava
• gstest gstest
• gsviewer gsviewer

Platform & setup

Building Ghostscript

Ghostscript should be built as a shared library for your platform.

See Building Ghostscript.

jni: Building the Java Native Interface

Before building the JNI ensure that Ghostscript has already been built for your platform and that you have JDK installed.

The JNI is for use in the Java interface, this object must be placed somewhere on your Java PATH. On Windows, the DLL can be placed in the working directory, next to gsjava.jar.

Preparing your include folder

The build scripts require the header jni.h, which defines all JNI functions, and jni_md.h, which defines all system-specific integer types. The build scripts expect an include folder relative to their location which contain these header files from your system.

These headers are typically found in the following directories:

Once your include folder has been located folder you can copy it and place it in your ghostpdl/demos/java/jni/gs_jni folder.

Your build scripts should now be ready to run as they will be able to find the required JNI header files in their own relative include folder.

Building on Windows

The jni folder contains a Visual Studio Solution file /jni/gs_jni/gs_jni.sln which you should use to build the required JNI gs_jni.dll library file.

With the project open in Visual Studio, select the required architecture from the drop down - then right click on 'gs_jni' in the solution explorer and choose "Build".

Building on MacOS

On your command line, navigate to ghostpdl/demos/java/jni/gs_jni and ensure that the build script is executable and then run it, with:

chmod +x build_darwin.sh
./build_darwin.sh

Building on Linux

On your command line, navigate to ghostpdl/demos/java/jni/gs_jni and ensure that the build script is executable and then run it, with:

chmod +x build_linux.sh
./build_linux.sh

gsjava: Building the JAR

Building with the command line

Navigate to ghostpdl/demos/java/gsjava and use the following:

NOTE
gsjava has a dependancy on jni, please ensure that gs_jni is able to be built beforehand.

Building with Eclipse

Alternatively you can use Eclipse to build the JAR file.

Using Eclipse import the source folder gsjava as a project and select Export > Java > JAR File as shown in the screenshot example below:

Linking the JAR

The built JAR should be properly linked within your project Java Build Path as follows:

Demo projects

gstest

This project can be opened in Eclipse and used to test the Ghostscript API. The sample here simply sets up an instance of Ghostscript and then sets and gets some parameters accordingly.

gsviewer

This project can be used to test the Ghostscript API alongside a UI which handles opening PostScript and PDF files. The sample application here allows for file browsing and Ghostscript file viewing.

Below is a screenshot of the sample application with a PDF open:

To run the project navigate to the demos/java/gsviewer location and ensure that the required libraries are in the directory:

Building on Windows

Run the build_win32.bat script.

Running on Windows

To run, open gsviewer.jar either through File Explorer or in the command line through the following command:

java -jar gsviewer.jar

Building on MacOS

On your command line, navigate to ghostpdl/demos/java/gsviewer and ensure that the build script is executable and then run it, with:

chmod +x build_darwin.sh
./build_darwin.sh

This will automatically build gs_jni.dylib (in the ghostpdl/demos/java/jni/gs_jni/ location) and gsjava.jar gsviewer.jar in the gsviewer directory.

Running on MacOS

Ensure that the Ghostscript library exists in the gsviewer directory. (Copy and move the built library from ghostpdl/sobin as required).

Ensure that the run script is executable and then run it, with:

chmod +x start_darwin.sh
./start_darwin.sh

Building on Linux

On your command line, navigate to ghostpdl/demos/java/gsviewer and ensure that the build script is executable and then run it, with:

chmod +x build_linux.sh
./build_linux.sh

This will automatically build gs_jni.so (in the ghostpdl/demos/java/jni/gs_jni/ location) and gsjava.jar gsviewer.jar in the gsviewer directory.

NOTE
On Linux, when using OpenJDK, the property "assistive_technologies" may need to be modified for the Java code to build. It can be modified by editing the "accessibility.properties" file. This is located at:

/etc/java-8-openjdk/accessibility.properties

Running on Linux

Ensure that the Ghostscript library exists in the gsviewer directory. (Copy and move the built library from ghostpdl/sobin as required).

Ensure that the run script is executable and then run it, with:

chmod +x start_linux.sh
./start_linux.sh