improve/modernize some error messages

Signed-off-by: Gavin King <gavin@hibernate.org>

hibernate-core/src/main/java/org/hibernate/NonUniqueObjectException.java

@@ -41,7 +41,7 @@ public class NonUniqueObjectException extends HibernateException {
 	 */
 	public NonUniqueObjectException(Object entityId, String entityName) {
 		this(
-				"A different object with the same identifier value was already associated with the session",
+				"A different object with the same identifier value was already associated with this persistence context",
 				entityId,
 				entityName
 		);

hibernate-core/src/main/java/org/hibernate/StaleObjectStateException.java

@@ -25,8 +25,7 @@ public class StaleObjectStateException extends StaleStateException {
 	 * @param identifier The identifier of the entity
 	 */
 	public StaleObjectStateException(String entityName, Object identifier) {
-		this( entityName, identifier,
-				"Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect)" );
+		this( entityName, identifier, "Row was already updated or deleted by another transaction" );
 	}
 
 	/**

hibernate-core/src/main/java/org/hibernate/StaleStateException.java

@@ -9,11 +9,8 @@ package org.hibernate;
 /**
  * Thrown when a version number or timestamp check failed, indicating that
  * the {@link Session} contained stale data (when using long transactions
- * with versioning). Also occurs if we try to delete or update a row that
+ * with versioning). Also occurs on attempts to delete or update a row that
  * does not exist.
- * <p>
- * Note that this exception sometimes indicates that the user failed to
- * specify the correct {@code unsaved-value} strategy for an entity.
  *
  * @author Gavin King
  */

hibernate-core/src/main/java/org/hibernate/UnsupportedLockAttemptException.java

@@ -7,7 +7,9 @@
 package org.hibernate;
 
 /**
- * This exception is thrown when an invalid {@link LockMode} is selected for an entity.
+ * Thrown when an invalid {@link LockMode} is requested for a given entity, in
+ * particular, when a {@linkplain Session#setReadOnly(Object, boolean) read only}
+ * entity is locked with a mode stricter than {@link LockMode#READ READ}.
  *
  * @author John O'Hara
  */

hibernate-core/src/main/java/org/hibernate/engine/internal/ImmutableEntityEntry.java

@@ -84,13 +84,12 @@ public final class ImmutableEntityEntry extends AbstractEntityEntry {
 
 	@Override
 	public void setLockMode(LockMode lockMode) {
-		switch ( lockMode ) {
-			case NONE:
-			case READ:
-				setCompressedValue( LOCK_MODE, lockMode );
-				break;
-			default:
-				throw new UnsupportedLockAttemptException( "Lock mode not supported" );
+		if ( lockMode.greaterThan(LockMode.READ) ) {
+			throw new UnsupportedLockAttemptException( "Lock mode "
+					+ lockMode + " not supported for read-only entity" );
+		}
+		else {
+			setCompressedValue( LOCK_MODE, lockMode );
 		}
 	}