@Override
	public boolean getAllPossibleValues(List<Completion> completions, Class<?> targetType, String existingData,
			String optionContext, MethodTarget target) {
		String start = (existingData.startsWith("'") || existingData.startsWith("\"")) ? existingData.substring(1)
				: existingData;

		CompletionKind kind = determineKind(optionContext);
		try {
			int successiveInvocations = determinceNumberOfInvocations(optionContext);
			List<String> candidates = completionOperations().completions(kind, start, successiveInvocations);
			for (String candidate : candidates) {
				completions.add(new Completion(candidate));
			}
			return false;
		}
		// Protect from exception in non-command code
		catch (Exception e) {
			return false;
		}
	}
To appear in the optionContext. Triggers the use of this converter and specifies which kind of completion is
expected.
spring-xd-shell/src/main/java/org/springframework/xd/shell/converter/CompletionConverter.java