In previous blog entry We learnt about upload simple file to google blob store using Guice and GIN with GWT. Now in this I shall describe a technique for uploading image to blob store and displaying it back on the gwt page. Example Code can be downloaded from http://code.google.com/p/gwt-image-file-upload/. While uploading file into blobstore use [...]
Archive for the ‘GWT’ Category
GWT blob upload Exception
Posted by _AB on July 19th, 2011
Uncaught exception from servlet java.lang.IllegalStateException: Must be called from a blob upload callback request. This is because Upload Url should be generated from Server on run time and form submitted on that action. for example, you need to get file upload through blobstoreService.createUploadUrl(“/data/upload”). what ever it returns submit file on that URL.
GWT/GAE File Upload Using Guice and Gin
Posted by _AB on July 19th, 2011
Client Side: 1- create Upload form in new dialog box public class UploadDialog extends DialogBox { private void createForm(){ VerticalPanel panel = new VerticalPanel(); form = new FormPanel(); [...]
Posted in GWT, Java 
Tags: blob upload, GAE file upload servlet, Gin Guice dispatch, GWT file Upload 
1 Comment »Assert in GWT
Posted by _AB on June 29th, 2011
Asserts are removed when compiled to javascript. Use asserts for things that are so wrong that it’s a programming error that ought to be caught in development mode, and you don’t want to pay any overhead in production for it.
Coding Basics – Compatibility with the Java Language and Libraries – Google Web Toolkit – Google Code
Posted by _AB on June 29th, 2011
Language support GWT supports most of the core Java language syntax and semantics, but there are a few differences you will want to be aware of. Note: As of GWT 1.5, GWT compiles the Java language syntax that is compatible with J2SE 1.5 or earlier. Versions of GWT prior to GWT 1.5 are limited to [...]
Posted in GWT Tags: GWT coding basics, GWT compatibility with Java Language, Language support 7 Comments »GAE – upload file blobstore exception
Posted by _AB on June 27th, 2011
When I run the GAE local server, the BlobStorage service works fine. When I run the GWT/GAE project in GWT development mode, however, the blob store service doesn’t work: Problem accessing /_ah/upload/aglhbHRhaXN0YXRyGwsSFV9fQmxvYlVwbG9hZFNlc3Npb25fXxgBDA. Reason: Must call one of set*BlobStorage() first. Caused by: java.lang.IllegalStateException: Must call one of set*BlobStorage() first. at Solution I’ve been able to resolve [...]
Posted in GWT Tags: BlobStorage, GAE, GWT development mode, java.lang.IllegalStateException No Comments »How do I speed up the gwt compiler?
Posted by _AB on June 13th, 2011
Let’s start with the uncomfortable truth: GWT compiler performance is really lousy. You can use some hacks here and there, but you’re not going to get significantly better performance. A nice performance hack you can do is to compile for only specific browsers, by inserting the following line in your gwt.xml: <define-property name=”user.agent” values=”ie6,gecko,gecko1_8″></define-property> or in [...]
Minimizing work – Google App Engine – Google Code
Posted by _AB on June 2nd, 2011
Paging without using offset Paging is a convenient way of presenting users with a large amount of information without overwhelming them or exacerbating load times. The concept is simple—instead of displaying all data on a single screen, only a subset of the data is displayed, like a listing of search results in your favorite search [...]
