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gwt-openlayers-devl
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From: Edwin C. <com...@gm...> - 2010-02-10 15:39:40
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Hi Nishant, GWT-OpenLayers is a wrapper library for the OpenLayers Javascript library, so GWT projects can use OpenLayers functionality without having to implement the JSNI wrapper code themselves. In an ideal world it would be a plain GWT port of OpenLayers, but for now it leverages the momentum of OpenLayers. Add 1) There is currently no overview of which functionality is wrapped by GWT-OL exactly. However, most of the stuff for working with OGC WMS/WFS webservices and vector layers has been wrapped. Recently also the vector feature manipulations controls (modify, drag, rotate features) have been wrapped and the WFS protocol has been implemented. The GWT-OL codebase has evolved mainly on the basis of the needs of the developers. There has been some work on third-party layers (Google, ArcGiS), but I cannot tell you the status of the support for these layers, as I do not have showcase examples for them yet and have not used them myself. Add 2) First of all GWT-OL wraps OpenLayers, so bugs in OpenLayers are also in GWT-OL. There are no pressing bugs that I can think of in GWT-OL specifically. The most pressing things are extending the showcase with more examples and providing more documentation to users of the API. My current focus is adding a simple open proxy implementation, which should make it easy to use WFS protocol and make a showcase example for that. There is off course more functionality of OpenLayers that I'd like to see wrapped, but the infrastructure for wrapping OpenLayers is good in place. Add 3) MapFish is a solution with client and server side components. The client side components are build on top of OpenLayers and recently GeoExt, which itself uses OpenLayers for the map component and Ext-JS for the GUI components. GeoExt in turn is building stuff to interface with the MapFish print service. GeoExt and MapFish provide stuff for building GIS applications that is not in OpenLayers, but tie you into Ext-JS for the GUI. The only true comparison you can make is GWT-OpenLayers with OpenLayers. If you're doing everything in JavaScript then you should be using OpenLayers and if you are also using Ext-JS then have a look at GeoExt and MapFish. However, if you are developing with GWT, which itself gives you a lof of benefits over developing in Javascript (see for example: http://www.keylimetie.com/Blog/2009/3/11/why-choose-gwt/), then you cannot simply use OpenLayers, but need GWT-OpenLayers. Ad 4) There is no roadmap past the one for version 0.5 (https://sourceforge.net/apps/trac/gwt-openlayers/roadmap), but the ultimate goals are: - to wrap all OpenLayers offers - provide tight GWT integration (using GWT widgets in popups etc) In tandem to those goals it would be nice if a plain GWT web mapping library gets of the ground. That would preferably be when Vector Graphics hit GWT to implement Vector Layers. There is already a GWTCanvas in incubator: http://code.google.com/p/google-web-toolkit-incubator/wiki/GWTCanvas and there are other iniatives like: http://code.google.com/p/gwt-canvas/ http://code.google.com/p/gwt-g2d/ http://vaadin.com/web/hene/wiki/-/wiki/Main/GWT+Graphics Greetings, Edwin On 10 February 2010 14:15, nishant verma <nis...@gm...> wrote: > Hi > > I am currently a developer in OpenXdata project > http://www.openxdata.org/. OpenXdata is an open-source, enterprise, > end-to-end software solution for any type of forms based data collection and > management using mobile devices and web forms. > > We are now looking for developing a web-based GIS application > for OpenXdata. We were searching for various open-source GIS web frameworks, > when we came across your project at > http://sourceforge.net/projects/gwt-openlayers/. We have also looked at > OpenLayers, MapFish etc. But on sourceforge, we couldn't find answers to > some questions we have. In this context, on behalf of OpenXdata, I would > like to ask you a few questions: > > 1) What all functionalities of OpenLayers does GWT-OpenLayers support? On > this link > http://geoserver.org/display/GEOSDOC/Google+Web+Toolkit+(GWT),+OpenLayers+and+GeoServer, > we could find a mention of some of the functionalities, but seems like this > is an old documentation and refers to GWT-OpenLayers 0.1. > > 2) What are the most pressing bugs that GWT-OpenLayers is facing? > > 3) What are the key benefits when compared to other frameworks like MapFish? > > 4) What is the road map for this project? Does it strive to provide all the > functionality of OpenLayers in future versions? > > I will be grateful to get a reply. Please feel free to ask any questions. > > Regards, > Nishant > |
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From: Edwin C. <com...@gm...> - 2010-02-12 17:28:06
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Hi Nishant, The GWT-OpenLayers library is wrapped using JSNI (http://code.google.com/webtoolkit/doc/latest/DevGuideCodingBasicsJSNI.html), but it uses JSObject, which decorates JavascriptObject with some convenience methods, so less JSNI code is needed. The approach that was taken was to use composite wrapper classes, so everything in GWT-OpenLayers is a JSObjectWrapper that keeps on to the JSObject it wraps. If there is JSNI code this is put in a separate Impl file. Overlay types are not used for multiple reasons: - a cleaner API can be achieved with JSObjectWrapper, as methods on JSObject are not automatically on the object extending JSObjectWrapper - Overlay types have to have a default constructor - Overlay types cannot be used for creating JavaScript objects from scratch (read: OpenLayers configuration objects) When no arrays of objects are returned or have to go into a method, than wrapping is straightforward. The code is online browsable. Simple examples are perhaps the base types such as Pixel: http://gwt-openlayers.hg.sourceforge.net/hgweb/gwt-openlayers/gwt-openlayers/file/ Let me know if that is what you were looking for... If you want to contribute to GWT-OL it will not be problematic to grant you access to do that. I try to keep the entry bar low for that. Greeting, Edwin On 12 February 2010 14:21, nishant verma <nis...@gm...> wrote: > Hi Edwin, > > Thanks for your reply. I have one question. Lets say we start > using GWT-OpenLayers in our application, but later find that there is some > functionality of OpenLayers which is not provided by GWT-Openlayers, then > how can we wrap those required functionalities into java code. Can you give > us a simple example of how this is done currently. May be we could ourselves > expand GWT-Openlayers library according to our requirements and thereby also > be able to contribute to your project. > > Regards, > Nishant > > On Wed, Feb 10, 2010 at 9:09 PM, Edwin Commandeur > <com...@gm...> wrote: >> >> Hi Nishant, >> >> GWT-OpenLayers is a wrapper library for the OpenLayers Javascript >> library, so GWT projects can use OpenLayers functionality without >> having to implement the JSNI wrapper code themselves. >> >> In an ideal world it would be a plain GWT port of OpenLayers, but for >> now it leverages the momentum of OpenLayers. >> >> Add 1) There is currently no overview of which functionality is >> wrapped by GWT-OL exactly. However, most of the stuff for working with >> OGC WMS/WFS webservices and vector layers has been wrapped. Recently >> also the vector feature manipulations controls (modify, drag, rotate >> features) have been wrapped and the WFS protocol has been implemented. >> The GWT-OL codebase has evolved mainly on the basis of the needs of >> the developers. There has been some work on third-party layers >> (Google, ArcGiS), but I cannot tell you the status of the support for >> these layers, as I do not have showcase examples for them yet and have >> not used them myself. >> >> Add 2) First of all GWT-OL wraps OpenLayers, so bugs in OpenLayers are >> also in GWT-OL. There are no pressing bugs that I can think of in >> GWT-OL specifically. The most pressing things are extending the >> showcase with more examples and providing more documentation to users >> of the API. My current focus is adding a simple open proxy >> implementation, which should make it easy to use WFS protocol and make >> a showcase example for that. >> There is off course more functionality of OpenLayers that I'd like to >> see wrapped, but the infrastructure for wrapping OpenLayers is good in >> place. >> >> Add 3) MapFish is a solution with client and server side components. >> The client side components are build on top of OpenLayers and recently >> GeoExt, which itself uses OpenLayers for the map component and Ext-JS >> for the GUI components. GeoExt in turn is building stuff to interface >> with the MapFish print service. GeoExt and MapFish provide stuff for >> building GIS applications that is not in OpenLayers, but tie you into >> Ext-JS for the GUI. >> The only true comparison you can make is GWT-OpenLayers with >> OpenLayers. If you're doing everything in JavaScript then you should >> be using OpenLayers and if you are also using Ext-JS then have a look >> at GeoExt and MapFish. However, if you are developing with GWT, which >> itself gives you a lof of benefits over developing in Javascript (see >> for example: http://www.keylimetie.com/Blog/2009/3/11/why-choose-gwt/), >> then you cannot simply use OpenLayers, but need GWT-OpenLayers. >> >> Ad 4) There is no roadmap past the one for version 0.5 >> (https://sourceforge.net/apps/trac/gwt-openlayers/roadmap), but the >> ultimate goals are: >> - to wrap all OpenLayers offers >> - provide tight GWT integration (using GWT widgets in popups etc) >> >> In tandem to those goals it would be nice if a plain GWT web mapping >> library gets of the ground. That would preferably be when Vector >> Graphics hit GWT to implement Vector Layers. There is already a >> GWTCanvas in incubator: >> http://code.google.com/p/google-web-toolkit-incubator/wiki/GWTCanvas >> and there are other iniatives like: >> http://code.google.com/p/gwt-canvas/ >> http://code.google.com/p/gwt-g2d/ >> http://vaadin.com/web/hene/wiki/-/wiki/Main/GWT+Graphics >> >> Greetings, >> Edwin >> >> On 10 February 2010 14:15, nishant verma <nis...@gm...> wrote: >> > Hi >> > >> > I am currently a developer in OpenXdata project >> > http://www.openxdata.org/. OpenXdata is an open-source, enterprise, >> > end-to-end software solution for any type of forms based data collection >> > and >> > management using mobile devices and web forms. >> > >> > We are now looking for developing a web-based GIS >> > application >> > for OpenXdata. We were searching for various open-source GIS web >> > frameworks, >> > when we came across your project at >> > http://sourceforge.net/projects/gwt-openlayers/. We have also looked at >> > OpenLayers, MapFish etc. But on sourceforge, we couldn't find answers to >> > some questions we have. In this context, on behalf of OpenXdata, I would >> > like to ask you a few questions: >> > >> > 1) What all functionalities of OpenLayers does GWT-OpenLayers support? >> > On >> > this link >> > >> > http://geoserver.org/display/GEOSDOC/Google+Web+Toolkit+(GWT),+OpenLayers+and+GeoServer, >> > we could find a mention of some of the functionalities, but seems like >> > this >> > is an old documentation and refers to GWT-OpenLayers 0.1. >> > >> > 2) What are the most pressing bugs that GWT-OpenLayers is facing? >> > >> > 3) What are the key benefits when compared to other frameworks like >> > MapFish? >> > >> > 4) What is the road map for this project? Does it strive to provide all >> > the >> > functionality of OpenLayers in future versions? >> > >> > I will be grateful to get a reply. Please feel free to ask any >> > questions. >> > >> > Regards, >> > Nishant >> > > > |
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