ZOO-Project WPS Java-API and JGrasstools Java Hydrological Toolbox

The ZOO-Project (http://zoo-project.org/) is a solid Open Geospatial Consortium (OGC) Web Processing Service (WPS - http://www.opengeospatial.org/standards/wps) standard server implementation with an open flexible API that works well with many different programming languages. The Java bindings have never been tested in advanced configurations and complex data types, and to date only implement the minimum necessary interfaces. The JGrasstools project is a modular processing library and its highly annotated nature makes it possible to adapt quite easily to other toolboxes. JGrasstools contains a wide variety of powerful and efficient GIS, hydrology and geomorphological tools and processes, that can be exposed to and used by other libraries and toolkits. One example has been the adaptation to the Geotools Process API. The JGrasstools project, as well as other java based projects (as JTS, Sextante or even Geotools) would benefit greatly from the possibility to be used within a web-enabled WPS execution environment, as well as being integrated with the open standards suite of the OGC.  Some time ago Moovida tried integrating the JGrasstools libraries with the ZOO-Project Java binding to expose them as native WPS processes. This would allow them to work inside the ZOO-Project and serve its modules under the WPS standard.

Some Background

The ZOO-Project WPS implementation is a flexible, modular high performance HTTP CGI implementation. ZOO-Kernel is a powerful server-side C Kernel which makes it possible to manage and chain Web services, by loading dynamic libraries and handling them as on-demand Web services. The ZOO Kernel is written in C language, and supports several common programming languages in order to connect to numerous libraries and models (http://zoo-project.org/trac/wiki/ZooWebSite/ZooKernel). The generic ZOO API is basically accessible for every possible programming and web scripting language that can be run under the CGI interface. Main API implementations, the ZOO services, are available for C/C++, Python, JavaScript, PHP, Fortran and Java. Some API bindings are more advanced and complete and make the full ZOO-API (http://zoo-project.org/trac/wiki/ZooWebSite/ZOOAPI/Classes#ZOOAPIClasses) accessible to the ZOO service in the particular programming language (e.g. C, Python or JavaScript). In comparison the the Java API binding only exposes the minimum functionality to run from the ZOO Kernel.

JGrasstools (http://moovida.github.io/jgrasstools/) is a powerful GIS toolkits with functionality reaching from standard geoprocessing algorithms to advanced processing features used in hydrology and geomorphology. JGrasstools is based on a Maven (http://maven.apache.org/) build process, which takes care of dependency resolution and creating the succinct jar packages with the compiled classes. Maven is a defacto standard for managing (source and dependencies) building and deploying (jar packaging, resources, copying, publishing, archiving and installing) Java-based software projects. JGrasstools is also used as a toolbox in the uDig desktop GIS software (http://udig.refractions.net/). If JGrasstools could be exposed via a open standards and interfaces, web-based processing and execution environment (like ZOO-Project provides) it can be widely used in WebGIS deployments and large scale cloud based processing chains.

The next level

Andrea from Moovida said he didn't have enough time to continue developing this idea. He developed a generator which would programmatically scan through the annotated JGrasstools modules and generate respective ZooJavaWps classes per JGrasstools module/method and the corresponding ZOO-Project .zcfg config file. The only struggle I had was getting the CLASSPATH properly set up, as the ZOO-Project is basically an HHTP CGI application which will start a JVM per request. When I picked up on this in preparation for a GSoC proposal, I found that there were a few little botches with the parameter mapping from ZOO Java API into the very nicely annotated JGrasstools methods. So I took one example generated (WPS-ified) JGrasstool process and adjusted the parameter mapping and got it running with ZOO-Project. Additionally I adjusted the JGrasstools Maven config files to download the necessary dependencies in the target folders to copy them collectively in the ZOO-Project Java CLASSPATH.

Unfortunately I also didn't have time to drive this further still. However, it is just soooo close really :-) Alternatively a 52North WPS implementation based on the super practical JGrasstools annotations and Andrea's generator would also be relatively straightforward.