Change status checking order in Cursor.inerator

See #1297

Author: kazuki43zoo

src/main/java/org/apache/ibatis/cursor/defaults/DefaultCursor.java

@@ -94,12 +94,12 @@ public int getCurrentIndex() {
 
     @Override
     public Iterator<T> iterator() {
-        if (isClosed()) {
-            throw new IllegalStateException("A Cursor is already closed.");
-        }
         if (iteratorRetrieved) {
             throw new IllegalStateException("Cannot open more than one iterator on a Cursor");
         }
+        if (isClosed()) {
+            throw new IllegalStateException("A Cursor is already closed.");
+        }
         iteratorRetrieved = true;
         return cursorIterator;
     }

src/test/java/org/apache/ibatis/submitted/cursor_simple/CursorSimpleTest.java

@@ -373,6 +373,19 @@ public void shouldThrowIllegalStateExceptionUsingIteratorOnSessionClosed() {
         } catch (IllegalStateException e) {
             Assert.assertEquals("A Cursor is already closed.", e.getMessage());
         }
+
+        // verify for checking order
+        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+            usersCursor = sqlSession.getMapper(Mapper.class).getAllUsers();
+            usersCursor.iterator();
+        }
+        try {
+            usersCursor.iterator();
+            Assert.fail("Should throws the IllegalStateException when call the iterator already.");
+        } catch (IllegalStateException e) {
+            Assert.assertEquals("Cannot open more than one iterator on a Cursor", e.getMessage());
+        }
+
     }
 
 }