Improve error message when JRE could not be located in the container.

- Guard against an NPE that may occur on initial loading of image tab

Change-Id: I85850b97d136e9d531cbf0eae164342c2befd734
Reviewed-on: https://git.eclipse.org/r/100073
Tested-by: Hudson CI
Reviewed-by: Roland Grunberg <rgrunber@redhat.com>

3 files changed, 9 insertions, 5 deletions

diff --git a/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/ContainerVMRunner.java b/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/ContainerVMRunner.java
index 2275110be5..a5016daa06 100644
--- a/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/ContainerVMRunner.java
+++ b/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/ContainerVMRunner.java
@@ -92,7 +92,7 @@ public class ContainerVMRunner extends StandardVMRunner {
 				exe = ((ContainerVMInstall)fVMInstance).getJavaExecutable();
 			}
 			if (exe == null) {
-				abort(NLS.bind(Messages.ContainerVMRunner_Unable_to_locate_executable_for__0__1, new String[]{fVMInstance.getName()}), null, IJavaLaunchConfigurationConstants.ERR_INTERNAL_ERROR);
+				abort(Messages.ContainerVMRunner_Unable_to_locate_executable_for__0__1, null, IJavaLaunchConfigurationConstants.ERR_INTERNAL_ERROR);
 			} else {
 				return exe.getAbsolutePath();
 			}
diff --git a/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/JavaImageTab.java b/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/JavaImageTab.java
index 102622be9e..6e1cf39729 100644
--- a/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/JavaImageTab.java
+++ b/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/JavaImageTab.java
@@ -73,9 +73,13 @@ public class JavaImageTab extends AbstractLaunchConfigurationTab {
 			@Override
 			public Object[] getElements(Object inputElement) {
 				IDockerConnection conn = (IDockerConnection) inputElement;
-				return conn.getImages().stream()
-						.filter(i -> ! i.repoTags().get(0).equals("<none>:<none>")) //$NON-NLS-1$
-						.toArray(size -> new IDockerImage[size]);
+				if (conn == null || conn.getImages() == null) {
+					return new Object[0];
+				} else {
+					return conn.getImages().stream()
+							.filter(i -> ! i.repoTags().get(0).equals("<none>:<none>")) //$NON-NLS-1$
+							.toArray(size -> new IDockerImage[size]);
+				}
 			}
 		});
 		imageCmb.setLabelProvider(new ColumnLabelProvider() {
diff --git a/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/messages.properties b/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/messages.properties
index 403e999468..74d72a0322 100644
--- a/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/messages.properties
+++ b/containers/org.eclipse.linuxtools.jdt.docker.launcher/src/org/eclipse/linuxtools/jdt/docker/launcher/messages.properties
@@ -1,5 +1,5 @@
 ContainerVMRunner_Specified_executable__0__does_not_exist_for__1__4=Specified executable {0} does not exist for {1}
-ContainerVMRunner_Unable_to_locate_executable_for__0__1=Unable to locate executable for {0}
+ContainerVMRunner_Unable_to_locate_executable_for__0__1=Unable to locate the JVM executable in the container. Please make sure that the selected image contains the Java Runtime Environment.
 ImageSelectionDialog_connection_label=Connection :
 ImageSelectionDialog_image_label=Image :
 ImageSelectionDialog_title=Image Selection