Update CharacterTypeHandler.java

first,this is a basic error, the condition statement miss the "" condition in if(...);
in this case, i execute the select sql statement, and the resultType include a property -- Character type, when the DataBase return a "", Mybatis will throw a Exception: index out of range, becasue the array's length is 0 in the statement -- "return columnValue.charAt(0);"

Author: mrsun002

src/main/java/org/apache/ibatis/type/CharacterTypeHandler.java

@@ -33,7 +33,7 @@ public void setNonNullParameter(PreparedStatement ps, int i, Character parameter
   @Override
   public Character getNullableResult(ResultSet rs, String columnName) throws SQLException {
     String columnValue = rs.getString(columnName);
-    if (columnValue != null) {
+    if (columnValue != null && columnValue != "") {
       return columnValue.charAt(0);
     } else {
       return null;
@@ -43,7 +43,7 @@ public Character getNullableResult(ResultSet rs, String columnName) throws SQLEx
   @Override
   public Character getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
     String columnValue = rs.getString(columnIndex);
-    if (columnValue != null) {
+    if (columnValue != null && columnValue != "") {
       return columnValue.charAt(0);
     } else {
       return null;
@@ -53,7 +53,7 @@ public Character getNullableResult(ResultSet rs, int columnIndex) throws SQLExce
   @Override
   public Character getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
     String columnValue = cs.getString(columnIndex);
-    if (columnValue != null) {
+    if (columnValue != null && columnValue != "") {
       return columnValue.charAt(0);
     } else {
       return null;