My second book “Java EE Development with Eclipse – Second Edition” has been published. One of the reasons I did not post much on the blog was this book. I had been working on the book for the past few months and I am very glad that it has been published now.
One of the challenges writing this book was the diverse topics that it covered – Servlets, JSP, JSF, JDO, EJB, JSM, SOAP, REST, Spring, Unit Testing, Debugging and trouble shooting performance and memory issues in Java applications. Separate books could be written, and books have been written, on some of these topics.
This book explains how to develop applications using these technology in Eclipse IDE. The focus is not just on how to use different technologies in JEE, but also on setting up development environment, testing, debugging and deploying applications developed using these technologies.
In an Eclipse RCP application I was working on recently, I had to implement a TreeViewer with in-place editing feature. It was not easy to find all the information required to implement this, so I thought I would explain it here.
First let’s take a simple example, where hierarchical data is displayed in a tree.
When any item in the tree is double clicked, I want to edit the value in-place.
Here is the code to create this tree, without editing support. I will first create a data model using a Map. To simplify the example, I am assuming only one level of hierarchy.
I had presented a tutorial on implementing Eclipse Editor plugin a couple of years ago. Recently when I started implementing a new Eclipse editor, I was looking for that presentation, but couldn’t find it easily. I like to use my blog as reference for myself, so I thought I would post my Eclipse editor tutorial here.
For the tutorial, I created a new language called VGL (Vector Graphics Language) and built Eclipse editor plugin for it. The language is not important, and just serves the purpose for explaining how to create an editor. The tutorial starts with defining the language and then incrementally builds features of a typical Eclipse editor. I created separate projects for each step in the tutorial. There are nine Eclipse projects. Download and import project in Eclipse for each step if you want to see how it is built incrementally. The last project contains all the editor features covered in this tutorial.
JFace TreeViewer is a very useful UI control for displaying hierarchical data. It is used extensively in Eclipse, for example in Project/Package/Navigator view, Outline view, Debug Variables view etc. Eclipse .org hosts a nice article on TreeViewer – How to use the JFace Tree Viewer.
To specify data and its hierarchy in the TreeViewer, you implement ITreeContentProvider interface. This interface has methods like getElements, getChildren which you need to override to provide content and structure to the TreeViewer. You would typically return array of your model objects from getElements or getChildren methods. And since it is a tree view, you can expand or collapse the nodes. The model classes for an example in the above article could be Category (book, game etc.), Book and Game. Category can have Books or Games. You might load this information from a database and pass it to the content provider object. To refresh information in the TreeViewer, you would call one of the variants of refresh() function.
I spent quite a lot of time today trying to debug “Access restriction” error in one of my Eclipse plugins. In the last four years of Eclipse plugin development, I don’t recall ever facing this issue, but today suddenly some of the imports in one of the classes in my Eclipse plugin were flagged off as errors –
Access restriction: The type ISelection is not accessible due to restriction on required library <eclipse-path>\eclipse\plugins\org.eclipse.jface_3.6.1.M20100825-0800.jar
I had seen warnings about ‘restricted access’ for some of the imports earlier, but those were for classes that Eclipse discouraged to use e,g, for internal Eclipse classes. But today I was seeing errors.
The error does not tell much about what could have gone wrong. ISelection is exported from jface plugin and it is a public interface. And I had used this class without any error in other plugins.
I have been stuck with the problem of making UI widgets fill horizontally in a grid layout a few times. The solution is simple, but when I have to create UI using Eclipse SWT after a long gap, I tend to forget how I had made this work earlier, so I decided to blog about this.
I had to create a simple UI with one label and associated text box. I coded it like this –
GridLayout layout = new GridLayout(2, false);
tabContainer.setLayout(layout);//this is the parent composite
Label label1 = new Label(tabContainer, SWT.NONE);
GridData gd = new GridData();
gd.grabExcessHorizontalSpace = false;
Text txtBox1 = new Text(tabContainer, SWT.BORDER);
gd = new GridData();
gd.grabExcessHorizontalSpace = true;
I have been developing Eclipse plugins for more than four years now. I have implemented many features in the ColdFusion Builder, which is an Eclipse based IDE. Eclipse SDK provides a SWT Browser control which can be used within Eclipse plugin to display HTML files. Eclipse does not include any browser, but it uses the system browser- on Windows it is Internet Explorer and on Macintosh it is Safari. I have used this control mainly to display static HTML content or open a URL on a remote server, e.g. for executing ColdFusion Builder extensions written in CFML.