Improove messages and error handling.

src/core/lombok/core/configuration/JacksonVersion.java

@@ -15,7 +15,7 @@ public final class JacksonVersion implements ConfigurationValueType {
 	}
 
 	public static String exampleValue() {
-		return "2";
+		return "2, 3 or 2_3";
 	}
 
 	public static String description() {
@@ -31,8 +31,8 @@ public final class JacksonVersion implements ConfigurationValueType {
 			return _3;
 		} else if ("2_3".equals(value.trim())) {
 			return _23;
-		} else{
-			throw new IllegalArgumentException("Unsupported Jackson version selector. Supported values: 2, 3 or 2_3 ");
+		} else {
+			throw new IllegalArgumentException("Unsupported Jackson version selector.");
 		}
 	}
 

src/core/lombok/eclipse/handlers/HandleJacksonized.java

@@ -149,8 +149,8 @@ public class HandleJacksonized extends EclipseAnnotationHandler<Jacksonized> {
 		MemberValuePair builderMvp = new MemberValuePair("builder".toCharArray(), td.sourceStart, td.sourceEnd, builderClassLiteralAccess);
 
 		JacksonVersion jacksonVersion = annotationNode.getAst().readConfigurationOr(ConfigurationKeys.JACKSONIZED_JACKSON_VERSION, JacksonVersion._2);
-		if (! jacksonVersion.isValid()) {
-			annotationNode.addError("Usage: No valid jackson version selected");
+		if (jacksonVersion == null || !jacksonVersion.isValid()) {
+			annotationNode.addError("No valid jackson version selected.");
 			return;
 		}
 

src/core/lombok/javac/handlers/HandleJacksonized.java

@@ -175,8 +175,8 @@ public class HandleJacksonized extends JavacAnnotationHandler<Jacksonized> {
 		}
 
 		JacksonVersion jacksonVersion = annotationNode.getAst().readConfigurationOr(ConfigurationKeys.JACKSONIZED_JACKSON_VERSION, JacksonVersion._2);
-		if (! jacksonVersion.isValid()) {
-			annotationNode.addError("Usage: No valid jackson version selected");
+		if (jacksonVersion == null || !jacksonVersion.isValid()) {
+			annotationNode.addError("No valid jackson version selected.");
 			return;
 		}
 		if (jacksonVersion.useJackson2()) {