Wednesday, June 3, 2015

Generic drag and drop in eclipse

The default drag and drop from SWT relies on the fact that source and target both agree on certain transfer types. The source adds the drop data, the target has to know how to deal with that data.

A drop target in eclipse therefore cannot deal with unknown objects by default. Eg you cannot drop your plugin local objects on a Navigator view. This article describes how you can drop your own objects into existing eclipse views and how to enrich your local drop target with generic drop support.

Source code for this tutorial is available on github as a single zip archive, as a Team Project Set or you can browse the files online.

Step 1: Simple drag support

Lets start with default SWT drag support. Create a new Plug-in Project named com.codeandme.draganddrop. Add a new view with a Text element to it. Name the text element txtInput. I expect you are familiar with that procedure.

Now we add TextTransfer support:
  int operations = DND.DROP_MOVE | DND.DROP_COPY;
  DragSource source = new DragSource(txtInput, operations);

  Transfer[] types = new Transfer[] { TextTransfer.getInstance() };

  source.addDragListener(new DragSourceListener() {
   public void dragStart(DragSourceEvent event) {
    if (txtInput.getText().length() == 0)
     event.doit = false;

   public void dragSetData(DragSourceEvent event) {
    // for text drag to editors
    if (TextTransfer.getInstance().isSupportedType(event.dataType)) = txtInput.getSelectionText();

   public void dragFinished(DragSourceEvent event) {
This is default SWT dnd code, nothing special so far.

Step 1: Add drag support for generic objects

By default the action to be performed on a drop is implemented by the DropListener of the target. Fortunately eclipse provides a special transfer type that delegates the drop action to a dedicated class which we may provide in our plugin.

Switch to your plugin.xml and add a new Extension of type org.eclipse.ui.dropActions. Add an action element to it, set the id to com.codeandme.draganddrop.dropText and implement a class TextDropActionDelegate:
package com.codeandme.draganddrop;


import org.eclipse.core.resources.IContainer;
import org.eclipse.core.resources.IFile;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.NullProgressMonitor;
import org.eclipse.core.runtime.Path;
import org.eclipse.swt.widgets.Text;
import org.eclipse.ui.part.IDropActionDelegate;

public class TextDropActionDelegate implements IDropActionDelegate {

 public static final String ID = "com.codeandme.draganddrop.dropText";

 public boolean run(Object source, Object target) {
  if (source instanceof byte[]) {
   if (target instanceof IContainer) {
    IContainer parent = (IContainer) target;
    IFile file = parent.getFile(new Path("dropped text.txt"));
    if (!file.exists()) {
     try {
      file.create(new ByteArrayInputStream((byte[]) source), true, new NullProgressMonitor());
     } catch (CoreException e) {

    return true;

   } else if (target instanceof Text)
    ((Text) target).setText(new String((byte[]) source));

  return false;
The run() method gets called when the drop action is to be performed. The target is automatically set to the object under the mouse when we perform the drop, eg a folder in a Navigator view. The provided code is a bit simplified, eg we do not try to adapt the target in case it is not an IContainer.

Now we need to add our drop delegate to our source object. Switch back to your view and modify the code:
  Transfer[] types = new Transfer[] { TextTransfer.getInstance(), PluginTransfer.getInstance() };
add a new transfer type: PluginTransfer.
   public void dragSetData(DragSourceEvent event) {
    // for text drag to editors
    if (TextTransfer.getInstance().isSupportedType(event.dataType)) = txtInput.getSelectionText();

    // for plugin transfer drags to navigator views
    if (PluginTransfer.getInstance().isSupportedType(event.dataType)) = new PluginTransferData(TextDropActionDelegate.ID, txtInput.getSelectionText().getBytes());
When a plugin transfer is accepted by the target we need to set a PluginTransferData object that links to our action delegate and provides the source data.

Everything is in place, so give it a try: type and select some text in your view and drop it on a folder in the Project Explorer view.

Step 3: Add generic drop support to your own views

Generic drop support does not come entirely for free. If you want to add it to a JFace tree or table it is dead simple as that:

  int operations = DND.DROP_MOVE | DND.DROP_COPY;
  DropTarget target = new DropTarget(viewer.getControl(), operations);

  Transfer[] types = new Transfer[] { PluginTransfer.getInstance() };

  target.addDropListener(new PluginDropAdapter(viewer));
We may also reuse the PluginDropAdapter on simple Controls like text boxes. Therefore we need to overwrite some methods:
  target.addDropListener(new PluginDropAdapter(null) {
   protected int determineLocation(DropTargetEvent event) {
    return LOCATION_ON;

   protected Object getCurrentTarget() {
    return txtTarget;
If you provide drop support in general it is advised to add the plugin transfer type to allow other plugins to use your drop support.

Friday, May 22, 2015

Unit Testing with scripts in EASE

In the company I work for we do lots of regression testing, mostly for interface testing of hardware devices. Therefore we needed a unit testbench similar to JUnit without the complexity of writing java code for our tests. So we implemented a simple Unit test framework for EASE.

Source code for this tutorial is available in the EASE scripts repository.

Step 1: Create a simple test script

Create a new Project in your workspace named JavaScript Unit Testing Tutorial. Create a new file Tests/Simple/01 Valid tests.js
// starts a simple test
startTest("empty", "an empty test case");
// ends a test

// start another test
startTest("no test code", "a test containing no assertions");
print("Hi from valid test");

// third test
startTest("valid assertions", "a test containing valid assertions");
// check

// code outside of a testcase
print('"' + getTestFile() + '" completed');
You might ask where these test functions come from as we do not load any modules. The unit test framework comes with a module called Unittest. It is hidden by default but will be loaded automatically when we execute EASE UnitTests. To unhide go to the Preferences/Scripting/Modules (Note: this is not necessary to use the module, it will only display it in UI components).

If you are familiar with unit testing in general you also know assertions and according methods like assertTrue(). In general these methods perform a check for validity. In case an expected result does not match with a current result, an error is generated for the containing test case.

So test cases are encapsulated between a startTest() and an endTest(). It is recommended to not use assertions outside test cases, yet not mandatory.

Step 2: Create and execute a test suite

To execute test files, we need to create a Test Suite, that sets up a test environment for us. Create a new Scripting/Script Testsuite named Testsuite.suite.  The editor will allow you to select test files you want to execute. Therefore we look for script files in the same project where the suite is located.

Select our previously created test file and hit the Run Test Suite button in the top right corner.

 A new view is opened that displays unit test results.

The top tree view reflects the file structure of our test files and displays decorators indicating the test execution result. If you select a test file, detailed results are displayed in the bottom section.

Step 3: Test errors

Create a new file Tests/Simple/02 Test errors.js.
// test containing assertions that fail
startTest("invalid assertions", "a test containing invalid assertions");

// manually create a failure
startTest("failure", "test throwing a failure");
failure("test broken, stop execution here");

// an exception would also create a failure
throw new java.lang.Exception("code exception");

startTest("never to be reached");
// not being reached as the failure above terminates test file execution
Save the test, add it to your suite and run the suite right away. When an assertion fails, error markers are generated on your script files on the according code location. You will also see the most critical assertion reflected in the Script Unit Test view. Double clicking on errors will open the source editor on the corresponding location.

Similar to JUnit there exist two different types of things that can go wrong: errors and failures. Errors are assertions that do not meet their criteria. They are recoverable, meaning script execution of the test file continues.

Failures on the other hand are not recoverable, so script execution of that test file is terminated immediately.

Step 4: Test Suite configuration

Typically tests need to be adapted to a certain environment. In general you do not want test engineers to modify your script code. So the test suite supports setting of Variables that are automatically available in all test files. The Setup section allows to execute arbitrary code on the Test Suite start, Test File start, startTest() call and also for the corresponding teardown sections. As you may provide multiple suite files within a project, these secions are a good place to adapt tests according to your environment.

Optional: Test automation

Often tests need to be executed automatically, eg for a nightly test run. The Unittest module allows to run a testsuite from a script. Together with the headless application from EASE you can run a suite from the commandline and create a report (we currently support the JUnit xml format that can be picked up from Hudson/Jenkins).

Optional: Additional assertions

If you want to provide your own assertion methods, simply create your own module and let your wrapped method return an IAssertion. If you call your method from within a test script it will automatically validate your assertion method.

So why do I want to write scripted tests?

In the company I work for we use these kind of tests for interface verification of hardware devices. Therefore we provide our own modules that allow us to send stimuli and validate expected responses. We also use it in combination with analog measurement devices to verify that certain hardware parameters are within valid ranges.

Currently Script Unit Testing is supported for the Rhino script engine only.

Wednesday, April 8, 2015

Live charting with EASE

Recently we added charting support to EASE using the Nebula XY chart widget. Say you have a script acquiring some data you now may plot them as your measurement advances.

Step 1: Installation

For this tutorial you need to register the nebula update site:
in Preferences/Install/Update/Available Software Sites.

Afterwards install EASE and add EASE Charting Support to install all required modules. This component depends on Nebula Visualization Widgets, therefore we added the nebula update site before. Currently you have to stick to the nighty update site of EASE as charting is not part of the current release.

Step 2: Some example plots

Try out this little script to get these sample plots:

figure("Simple Charts");

series("linear", "m+");
for (x = 0; x <= 20; x += 1)
 plotPoint(x, x / 10 - 1);

series("1/x", "ko:");
for (x = 1; x <= 20; x += 0.2)
 plotPoint(x, 4/x);

series("sine", "bx");
for (x = 0; x < 20; x += 0.05)
 plotPoint(x, Math.sin(x) * Math.sin(3 * x));


series("drop", "gd");
for (t = 0; t < 2; t += 0.01)
 plotPoint(t, Math.pow(Math.E, t * -3) * Math.cos(t * 30));

series("upper limit", "rf--");
plot([0, 2], [0.4, 0.4]);

series("lower limit", "rf--");
plot([0, 2], [-0.4, -0.4]);
Run the script either in the Script Shell or execute it using launch targets.

Step 3: Charting Module API

The API of the charting module tries to keep close to MatLab style, so the format string for a series is almost identical. You may even omit to create figures or series and start plotting right away and we create everything necessary on the fly.

For a better user experience we extended the XYChart a bit by allowing to zoom directly using the scroll wheel either over the plot or its axis. Use a double click for an auto-zoom.

Sunday, February 22, 2015

Reformatting multiple source files

Recently I had to apply a new code formatter template to a project. Changing 50+ files by hand seemed to be too much monkey work. Writing a custom plug-in seemed to be too much work. Fortunately there is this great scripting framework to accomplish this task quite easily.

Step 1: Detecting affected source files

I have already blogged about EASE and how to install it. So I went directly to the script shell to fetch all java files form a certan project:

files = findFiles("*.java", getProject("org.eclipse.some.dedicated.project"), true)
Now we have an array of IFile instances. Easy, isn't it?

Step 2: The formatter script

Ideas how to format source files can be found in the forum. Taking the script and porting it to JS is simple:
function formatUnitSourceCode(file) {
 unit = org.eclipse.jdt.core.JavaCore.create(file);


 formatter = org.eclipse.jdt.core.ToolFactory.createCodeFormatter(null);
 range = unit.getSourceRange();
 formatEdit = formatter
       | org.eclipse.jdt.core.formatter.CodeFormatter.F_INCLUDE_COMMENTS,
     unit.getSource(), 0, unit.getSource().length(), 0, null);
 if (formatEdit.hasChildren()) {
  unit.applyTextEdit(formatEdit, null);
  unit.reconcile(org.eclipse.jdt.core.dom.AST.JLS4, false, null, null);

 unit.commitWorkingCopy(true, null);

Step 3: glueing it all together

Load the function into your script shell, fetch the list of files as in step 1 and then process all files in a loop:
for each (file in files) formatUnitSourceCode(file);
That's it. This short script uses your current source formatter settings and applies it to all selected files.

This little helper is available online in the EASE script repository.

Wednesday, January 14, 2015

EASE 0.1.0 - the very first release

I am proud to announce the very first release of the Eclipse Advanced Scripting Environment (EASE).

In case you have no idea what this is about, check out the project page. Afterwards you definitely need to install it right away in your IDE and start scripting.

Some facts: 
  • executes script code in your IDE, providing access to the running JRE and thus to the whole Eclipse API
  • supports JavaScript, Jython, Groovy and JRuby (see details)
  • allows to dynamically integrate scripts into toolbars and menus
  • extensible via script libraries (write your own)

This project started as an in house company solution some years ago. When I released it as open source back in 2013 I was quite astonished about the interest from the community. Soon this project moved into the e4 incubator which gave us a great chance to evolve and build up an infrastructure.
Last summer EASE was accepted as an Eclipse incubation project. With our first release we feel to be part of the eclipse community.

Let me take this opportunity to thank all the people who helped to make this happen. When I started out almost 2 years ago I did not expect to meet such an open minded community. So if you think of starting your own project I can just encourage you to take the first step. There are helping hands everywhere, trying to push you forward. Did I already say that I love this community?

XMLMemento: a simpe way to process XML files

Reading and writing simple XML files is a common task nowadays. Java comes with some powerful frameworks like SAX or Xerces to accomplish this task. But sometimes we look for something simpler. Today we will have a look at XMLMemento, a utility class by Eclipse that hides most of the complicated stuff from us.

Source code for this tutorial is available on googlecode as a single zip archive, as a Team Project Set or you can checkout the SVN projects directly. 


We will use following XML file for this tutorial
<?xml version="1.0" encoding="UTF-8"?>
 <project name="org.eclipse.ease">
  <description>EASE is a scripting environment for Eclipse. It allows to
   create, maintain and execute script code in the context of the
   running Eclipse instance.</description>
   <release version="0.1.0" />
   <release version="0.2.0" />
 <project name="org.eclipse.tycho">
   <release version="0.16.0" />
   <release version="0.17.0" />

The code samples below use a slightly modified version of XMLMemento. To reuse it more easily in non-Eclipse projects I removed Eclipse specific exceptions, messages and interfaces. If you intend to use XMLMemento within Eclipse, simply stick to the original version contained in the org.eclipse.ui.workbench plugin. For pure Java projects simply copy XMLMemento as it is used in this tutorial.

Step 1: Writing XML

First we need to create a root node. Afterwards we create child nodes and set their attributes.
package com.codeandme.xmlmemento;


import org.eclipse.ui.XMLMemento;

public class WriteXML {

 public static void main(String[] args) {

  XMLMemento rootNode = XMLMemento.createWriteRoot("root");

  // first project
  XMLMemento projectNode = rootNode.createChild("project");
  projectNode.putString("name", "org.eclipse.ease");
    "EASE is a scripting environment for Eclipse. It allows to create, maintain and execute script code in the context of the running Eclipse instance.");

  XMLMemento releasesNode = projectNode.createChild("releases");
  releasesNode.createChild("release").putString("version", "0.1.0");
  releasesNode.createChild("release").putString("version", "0.2.0");

  // second project
  projectNode = rootNode.createChild("project");
  projectNode.putString("name", "org.eclipse.tycho");

  releasesNode = projectNode.createChild("releases");
  releasesNode.createChild("release").putString("version", "0.16.0");
  releasesNode.createChild("release").putString("version", "0.17.0");

  // output to console

  // write to file
  try {
   File tempFile = new File("XML sample.xml");
   FileWriter fileWriter = new FileWriter(tempFile);;

  } catch (IOException e) {
Line 13: create the root node
Line 16: create a child node below root
Line 17: set an attribute on project node
Line 20: set text content of a node
Line 36: serialize XML to String (uses node.toString())
Line 42: write XML to File

Step 2: reading XML

Reading XML is also very easy. Just create a read root and start traversing child elements:
package com.codeandme.xmlmemento;


import org.eclipse.ui.XMLMemento;

public class ReadXML {

 public static void main(String[] args) {
  try {
   XMLMemento rootNode = XMLMemento.createReadRoot(new FileReader("XML sample.xml"));

   for (XMLMemento node : rootNode.getChildren())
    System.out.println("\t" + node.getString("name"));

   System.out.println("EASE versions:");
   for (XMLMemento node : rootNode.getChildren("project")) {
    if ("org.eclipse.ease".equals(node.getString("name"))) {
     for (XMLMemento versionNode : node.getChild("releases").getChildren("release")) {
      System.out.println("\t" + versionNode.getString("version"));

  } catch (Exception e) {
LIne 11: parse input and extract the root node
Line 14: iterate over all child nodes
Line 15: read node attribute

Friday, December 5, 2014

EASE scripts conquer the UI

EASE just recently got extended to inject scripts into the UI. This means you may insert scripts into your view toolbars, menus and context menus. No need to deploy anything, just provide the script and add some keywords to it.

During this tutorial we will develop our script step by step. The final version is available from the EASE scripts repository.

To follow this tutorial you need to install EASE into your IDE/RCP.

Step 1: A very simple script

Our target will be to open a file browser on the current location selected in the Project Explorer view.

Create a General/Project in your workspace and a file Explore from here.js. To launch an external program we may use the Platform module:
// runProcess('krusader');
Now register your script location in the preferences: Scripting/Script Locations. Afterwards test your script by running it using one of the follwing methods:
  • double click in the Script Explorer view
  • right click in Project Explorer and select Run As/EASE Script
  • D&D script file to Script Shell view
Step 2: Bind to toolbar

As a next step we want to attach our script to the toolbar. So open your script file again and add following comment at the top of the file:
// ********************************************************************************
// name                 : Explore from here
// toolbar              : Project Explorer
// script-type          : JavaScript
// description          : Start a file browser using current selection.
// ********************************************************************************
The new toolbar button appears right after saving the script file. No need to restart eclipse! If not you probably did not set up your script locations in preferences correctly.
The toolbar keyword accepts view titles and view IDs if you know them. All supported keywords are listed in the wiki.

Step 3: Using the current selection

When starting the file browser we want to use the current selection as our start folder. it can be easily consumed by using getSelection() from the UI module:

var selection = getSelection();
if (selection instanceof org.eclipse.jface.viewers.IStructuredSelection)
 selection = selection.getFirstElement();

if (selection instanceof org.eclipse.core.resources.IFile)
 selection = selection.getParent();

if (selection instanceof org.eclipse.core.resources.IContainer)
// runProcess("/usr/bin/krusader", ["--left", getSystemProperty("user.home"), "--right", selection.getRawLocation()]);
 runProcess("explorer.exe", [selection.getRawLocation()]);
First we extract the very first element of the current selection. In case it is a file, we get its parent folder. Finally check that we really have a container, then open the file browser.

Step 4: Adding a context menu entry

We might also want to bind our script to any IResource context menu in our application. This is really simple, just add following keyword to the header:
// popup                : enableFor(org.eclipse.core.resources.IResource)

Step 5: Adding an image to the toolbar

Instead of having a text button in the Project Explorer toolbar we may replace it with an image. You guessed it, its just another keyword:
// image                : platform:/plugin/org.eclipse.ease.ui/icons/eobj16/folder.png
This URI reuses an icon stored within the ease.ui plugin. You may use relative paths, file system paths or even http URIs for your images.
When you start building up your own script library, consider pushing your scripts to our script sample repository.