Handling checked exceptions for eclipse plugin - exception

Question

I am working on an Eclipse plugin and am faced with checked exceptions thrown from the API that I am using in my plugin. What is the practice around handling such exceptions in the context of a plugin? I could not find an appropriate Exception subclass from the Plugin development API.
Thanks in advance.

Answer 1

I use logging classes that I found in a book titled "Eclipse Plug-ins", by Eric Clayberg and Dan Rubel.
Here's the main logging class.
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Plugin;
import org.eclipse.core.runtime.Status;
public class EclipseLogging {
public static void logInfo(Plugin plugin, String pluginID, String message,
boolean display) {
log(plugin, pluginID, IStatus.INFO, IStatus.OK, message, null, display);
}
public static void logInfo(Plugin plugin, String pluginID,
Throwable exception) {
log(plugin, createStatus(pluginID, IStatus.ERROR, IStatus.OK,
"Unexpected Exception", exception));
}
public static void logInfo(Plugin plugin, String pluginID, String message,
Throwable exception) {
log(plugin, createStatus(pluginID, IStatus.ERROR, IStatus.OK, message,
exception));
}
public static void logError(Plugin plugin, String pluginID,
Throwable exception) {
logError(plugin, pluginID, "Unexpected Exception", exception);
}
public static void logError(Plugin plugin, String pluginID, String message,
Throwable exception) {
log(plugin, pluginID, IStatus.ERROR, IStatus.OK, message, exception,
true);
}
public static void log(Plugin plugin, String pluginID, int severity,
int code, String message, Throwable exception, boolean display) {
if (display) {
ExceptionAction action = new ExceptionAction(plugin, message,
exception);
action.run();
}
log(plugin, createStatus(pluginID, severity, code, message, exception));
}
public static IStatus createStatus(String pluginID, int severity, int code,
String message, Throwable exception) {
return new Status(severity, pluginID, code, message, exception);
}
public static void log(Plugin plugin, IStatus status) {
plugin.getLog().log(status);
}
}
And here's the exception action class.
import org.eclipse.core.runtime.Plugin;
import org.eclipse.jface.action.Action;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.IWorkbench;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PlatformUI;
public class ExceptionAction extends Action {
private Plugin plugin;
private String message;
private Throwable exception;
public ExceptionAction(Plugin plugin, String message, Throwable exception) {
this.plugin = plugin;
this.message = message;
this.exception = exception;
}
public void run() {
IWorkbench workbench = PlatformUI.getWorkbench();
IWorkbenchWindow window = workbench.getActiveWorkbenchWindow();
if (window != null) {
Shell parentShell = window.getShell();
parentShell.forceActive();
try {
ExceptionDetailsDialog dialog = new ExceptionDetailsDialog(
parentShell, null, null, message, exception, plugin);
dialog.open();
} catch (SWTException e) {
}
}
}
}
And finally, the classes to display the exception.
import org.eclipse.jface.dialogs.Dialog;
import org.eclipse.jface.dialogs.IDialogConstants;
import org.eclipse.jface.window.IShellProvider;
import org.eclipse.jface.window.SameShellProvider;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
/**
* An abstract dialog with a details section that can be shown or hidden by the
* user. Subclasses are responsible for providing the content of the details
* section.
*/
public abstract class AbstractDetailsDialog extends Dialog {
private final String title;
private final String message;
private final Image image;
private Button detailsButton;
private Control detailsArea;
private Point cachedWindowSize;
/**
* Construct a new instance with the specified elements. Note that the
* window will have no visual representation (no widgets) until it is told
* to open. By default, <code>open</code> blocks for dialogs.
*
* #param parentShell
* the parent shell, or <code>null</code> to create a top-level
* shell
* #param title
* the title for the dialog or <code>null</code> for none
* #param image
* the image to be displayed
* #param message
* the message to be displayed
*/
public AbstractDetailsDialog(Shell parentShell, String title, Image image,
String message) {
this(new SameShellProvider(parentShell), title, image, message);
}
/**
* Construct a new instance with the specified elements. Note that the
* window will have no visual representation (no widgets) until it is told
* to open. By default, <code>open</code> blocks for dialogs.
*
* #param parentShell
* the parent shell provider (not <code>null</code>)
* #param title
* the title for the dialog or <code>null</code> for none
* #param image
* the image to be displayed
* #param message
* the message to be displayed
*/
public AbstractDetailsDialog(IShellProvider parentShell, String title,
Image image, String message) {
super(parentShell);
this.title = title;
this.image = image;
this.message = message;
setShellStyle(SWT.DIALOG_TRIM | SWT.RESIZE | SWT.APPLICATION_MODAL);
}
/**
* Configures the given shell in preparation for opening this window in it.
* In our case, we set the title if one was provided.
*/
protected void configureShell(Shell shell) {
super.configureShell(shell);
if (title != null)
shell.setText(title);
}
/**
* Creates and returns the contents of the upper part of this dialog (above
* the button bar). This includes an image, if specified, and a message.
*
* #param parent
* the parent composite to contain the dialog area
* #return the dialog area control
*/
protected Control createDialogArea(Composite parent) {
Composite composite = (Composite) super.createDialogArea(parent);
composite.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
if (image != null) {
((GridLayout) composite.getLayout()).numColumns = 2;
Label label = new Label(composite, 0);
image.setBackground(label.getBackground());
label.setImage(image);
label.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_CENTER
| GridData.VERTICAL_ALIGN_BEGINNING));
}
Label label = new Label(composite, SWT.WRAP);
if (message != null)
label.setText(message);
GridData data = new GridData(GridData.FILL_HORIZONTAL
| GridData.VERTICAL_ALIGN_CENTER);
data.widthHint = convertHorizontalDLUsToPixels(IDialogConstants.MINIMUM_MESSAGE_AREA_WIDTH);
label.setLayoutData(data);
label.setFont(parent.getFont());
return composite;
}
/**
* Adds OK and Details buttons to this dialog's button bar.
*
* #param parent
* the button bar composite
*/
protected void createButtonsForButtonBar(Composite parent) {
createButton(parent, IDialogConstants.OK_ID, IDialogConstants.OK_LABEL,
false);
detailsButton = createButton(parent, IDialogConstants.DETAILS_ID,
IDialogConstants.SHOW_DETAILS_LABEL, false);
}
/**
* The buttonPressed() method is called when either the OK or Details
* buttons is pressed. We override this method to alternately show or hide
* the details area if the Details button is pressed.
*/
protected void buttonPressed(int id) {
if (id == IDialogConstants.DETAILS_ID)
toggleDetailsArea();
else
super.buttonPressed(id);
}
/**
* Toggles the unfolding of the details area. This is triggered by the user
* pressing the Details button.
*/
protected void toggleDetailsArea() {
Point oldWindowSize = getShell().getSize();
Point newWindowSize = cachedWindowSize;
cachedWindowSize = oldWindowSize;
// Show the details area.
if (detailsArea == null) {
detailsArea = createDetailsArea((Composite) getContents());
detailsButton.setText(IDialogConstants.HIDE_DETAILS_LABEL);
}
// Hide the details area.
else {
detailsArea.dispose();
detailsArea = null;
detailsButton.setText(IDialogConstants.SHOW_DETAILS_LABEL);
}
/*
* Must be sure to call getContents().computeSize(SWT.DEFAULT,
* SWT.DEFAULT) before calling getShell().setSize(newWindowSize) since
* controls have been added or removed.
*/
// Compute the new window size.
Point oldSize = getContents().getSize();
Point newSize = getContents().computeSize(SWT.DEFAULT, SWT.DEFAULT);
if (newWindowSize == null)
newWindowSize = new Point(oldWindowSize.x, oldWindowSize.y
+ (newSize.y - oldSize.y));
// Crop new window size to screen.
Point windowLoc = getShell().getLocation();
Rectangle screenArea = getContents().getDisplay().getClientArea();
final int pos = screenArea.height - (windowLoc.y - screenArea.y);
if (newWindowSize.y > pos)
newWindowSize.y = pos;
getShell().setSize(newWindowSize);
((Composite) getContents()).layout();
}
/**
* subclasses must implement createDetailsArea to provide content for the
* area of the dialog made visible when the Details button is clicked.
*
* #param parent
* the details area parent
* #return the details area
*/
protected abstract Control createDetailsArea(Composite parent);
}
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.text.MessageFormat;
import java.util.Dictionary;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Plugin;
import org.eclipse.jface.dialogs.IDialogConstants;
import org.eclipse.jface.window.IShellProvider;
import org.eclipse.jface.window.SameShellProvider;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;
/**
* A dialog to display one or more errors to the user, as contained in an
* <code>IStatus</code> object along with the plug-in identifier, name, version
* and provider. If an error contains additional detailed information then a
* Details button is automatically supplied, which shows or hides an error
* details viewer when pressed by the user.
*
* #see org.eclipse.core.runtime.IStatus
*/
public class ExceptionDetailsDialog extends AbstractDetailsDialog {
/**
* The details to be shown ({#link Exception}, {#link IStatus}, or
* <code>null</code> if no details).
*/
private final Object details;
/**
* The plugin triggering this details dialog and whose information is to be
* shown in the details area or <code>null</code> if no plugin details
* should be shown.
*/
private final Plugin plugin;
/**
* Construct a new instance with the specified elements. Note that the
* window will have no visual representation (no widgets) until it is told
* to open. By default, <code>open</code> blocks for dialogs.
*
* #param parentShell
* the parent shell, or <code>null</code> to create a top-level
* shell
* #param title
* the title for the dialog or <code>null</code> for none
* #param image
* the image to be displayed
* #param message
* the message to be displayed
* #param details
* an object whose content is to be displayed in the details
* area, or <code>null</code> for none
* #param plugin
* The plugin triggering this deatils dialog and whose
* information is to be shown in the details area or
* <code>null</code> if no plugin details should be shown.
*/
public ExceptionDetailsDialog(Shell parentShell, String title, Image image,
String message, Object details, Plugin plugin) {
this(new SameShellProvider(parentShell), title, image, message,
details, plugin);
}
/**
* Construct a new instance with the specified elements. Note that the
* window will have no visual representation (no widgets) until it is told
* to open. By default, <code>open</code> blocks for dialogs.
*
* #param parentShell
* the parent shell provider (not <code>null</code>)
* #param title
* the title for the dialog or <code>null</code> for none
* #param image
* the image to be displayed
* #param message
* the message to be displayed
* #param details
* an object whose content is to be displayed in the details
* area, or <code>null</code> for none
* #param plugin
* The plugin triggering this deatils dialog and whose
* information is to be shown in the details area or
* <code>null</code> if no plugin details should be shown.
*/
public ExceptionDetailsDialog(IShellProvider parentShell, String title,
Image image, String message, Object details, Plugin plugin) {
super(parentShell, getTitle(title, details), getImage(image, details),
getMessage(message, details));
this.details = details;
this.plugin = plugin;
}
/**
* Build content for the area of the dialog made visible when the Details
* button is clicked.
*
* #param parent
* the details area parent
* #return the details area
*/
protected Control createDetailsArea(Composite parent) {
// Create the details area.
Composite panel = new Composite(parent, SWT.NONE);
panel.setLayoutData(new GridData(GridData.FILL_BOTH));
GridLayout layout = new GridLayout();
layout.marginHeight = 0;
layout.marginWidth = 0;
panel.setLayout(layout);
// Create the details content.
createProductInfoArea(panel);
createDetailsViewer(panel);
return panel;
}
/**
* Create fields displaying the plugin information such as name, identifer,
* version and vendor. Do nothing if the plugin is not specified.
*
* #param parent
* the details area in which the fields are created
* #return the product info composite or <code>null</code> if no plugin
* specified.
*/
protected Composite createProductInfoArea(Composite parent) {
// If no plugin specified, then nothing to display here
if (plugin == null)
return null;
Composite composite = new Composite(parent, SWT.NULL);
composite.setLayoutData(new GridData());
GridLayout layout = new GridLayout();
layout.numColumns = 2;
layout.marginWidth = convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
composite.setLayout(layout);
Dictionary<?, ?> bundleHeaders = plugin.getBundle().getHeaders();
String pluginId = plugin.getBundle().getSymbolicName();
String pluginVendor = (String) bundleHeaders.get("Bundle-Vendor");
String pluginName = (String) bundleHeaders.get("Bundle-Name");
String pluginVersion = (String) bundleHeaders.get("Bundle-Version");
new Label(composite, SWT.NONE).setText("Provider:");
new Label(composite, SWT.NONE).setText(pluginVendor);
new Label(composite, SWT.NONE).setText("Plug-in Name:");
new Label(composite, SWT.NONE).setText(pluginName);
new Label(composite, SWT.NONE).setText("Plug-in ID:");
new Label(composite, SWT.NONE).setText(pluginId);
new Label(composite, SWT.NONE).setText("Version:");
new Label(composite, SWT.NONE).setText(pluginVersion);
return composite;
}
/**
* Create the details field based upon the details object. Do nothing if the
* details object is not specified.
*
* #param parent
* the details area in which the fields are created
* #return the details field
*/
protected Control createDetailsViewer(Composite parent) {
if (details == null)
return null;
Text text = new Text(parent, SWT.MULTI | SWT.READ_ONLY | SWT.BORDER
| SWT.H_SCROLL | SWT.V_SCROLL);
text.setLayoutData(new GridData(GridData.FILL_BOTH));
// Create the content.
StringWriter writer = new StringWriter(1000);
if (details instanceof Throwable)
appendException(new PrintWriter(writer), (Throwable) details);
else if (details instanceof IStatus)
appendStatus(new PrintWriter(writer), (IStatus) details, 0);
text.setText(writer.toString());
return text;
}
// /////////////////////////////////////////////////////////////////
//
// Utility methods for building content
//
// /////////////////////////////////////////////////////////////////
/**
* Answer the title based on the provided title and details object.
*/
public static String getTitle(String title, Object details) {
if (title != null)
return title;
if (details instanceof Throwable) {
Throwable e = (Throwable) details;
while (e instanceof InvocationTargetException)
e = ((InvocationTargetException) e).getTargetException();
String name = e.getClass().getName();
return name.substring(name.lastIndexOf('.') + 1);
}
return "Exception";
}
/**
* Answer the image based on the provided image and details object.
*/
public static Image getImage(Image image, Object details) {
if (image != null)
return image;
Display display = Display.getCurrent();
if (details instanceof IStatus) {
switch (((IStatus) details).getSeverity()) {
case IStatus.ERROR:
return display.getSystemImage(SWT.ICON_ERROR);
case IStatus.WARNING:
return display.getSystemImage(SWT.ICON_WARNING);
case IStatus.INFO:
return display.getSystemImage(SWT.ICON_INFORMATION);
case IStatus.OK:
return null;
}
}
return display.getSystemImage(SWT.ICON_ERROR);
}
/**
* Answer the message based on the provided message and details object.
*/
public static String getMessage(String message, Object details) {
if (details instanceof Throwable) {
Throwable e = (Throwable) details;
while (e instanceof InvocationTargetException)
e = ((InvocationTargetException) e).getTargetException();
if (message == null)
return e.toString();
return MessageFormat.format(message, new Object[] { e.toString() });
}
if (details instanceof IStatus) {
String statusMessage = ((IStatus) details).getMessage();
if (message == null)
return statusMessage;
return MessageFormat
.format(message, new Object[] { statusMessage });
}
if (message != null)
return message;
return "An Exception occurred.";
}
public static void appendException(PrintWriter writer, Throwable ex) {
if (ex instanceof CoreException) {
appendStatus(writer, ((CoreException) ex).getStatus(), 0);
writer.println();
}
appendStackTrace(writer, ex);
if (ex instanceof InvocationTargetException)
appendException(writer, ((InvocationTargetException) ex)
.getTargetException());
}
public static void appendStatus(PrintWriter writer, IStatus status,
int nesting) {
for (int i = 0; i < nesting; i++)
writer.print(" ");
writer.println(status.getMessage());
IStatus[] children = status.getChildren();
for (int i = 0; i < children.length; i++)
appendStatus(writer, children[i], nesting + 1);
}
public static void appendStackTrace(PrintWriter writer, Throwable ex) {
ex.printStackTrace(writer);
}
}