minor improvements

Author: wuchong

fluss-client/src/main/java/org/apache/fluss/client/converter/ConverterCommons.java

@@ -29,6 +29,8 @@
 import java.util.Map;
 import java.util.Set;
 
+import static org.apache.fluss.client.converter.RowToPojoConverter.charLengthExceptionMessage;
+
 /**
  * Internal shared utilities for POJO and Fluss InternalRow conversions.
  *
@@ -108,13 +110,9 @@ static void validateCompatibility(DataType fieldType, PojoType.Property prop) {
     }
 
     static BinaryString toBinaryStringForText(Object v, String fieldName, DataTypeRoot root) {
-        final String s =
-                (v instanceof Character) ? String.valueOf((Character) v) : String.valueOf(v);
+        final String s = String.valueOf(v);
         if (root == DataTypeRoot.CHAR && s.length() != 1) {
-            throw new IllegalArgumentException(
-                    String.format(
-                            "Field %s expects exactly one character for CHAR type, got length %d.",
-                            fieldName, s.length()));
+            throw new IllegalArgumentException(charLengthExceptionMessage(fieldName, s.length()));
         }
         return BinaryString.fromString(s);
     }

fluss-client/src/main/java/org/apache/fluss/client/converter/RowToPojoConverter.java

@@ -184,13 +184,10 @@ private static RowToField createRowReader(DataType fieldType, PojoType.Property
     private static Object convertTextValue(
             DataType fieldType, PojoType.Property prop, BinaryString s) {
         String v = s.toString();
-        String formattedMessage =
-                String.format(
-                        "Field %s expects exactly one character for CHAR type, got length %d.",
-                        prop.name, v.length());
         if (prop.type == String.class) {
             if (fieldType.getTypeRoot() == DataTypeRoot.CHAR && v.length() != 1) {
-                throw new IllegalArgumentException(formattedMessage);
+                throw new IllegalArgumentException(
+                        charLengthExceptionMessage(prop.name, v.length()));
             }
             return v;
         } else if (prop.type == Character.class) {
@@ -201,7 +198,8 @@ private static Object convertTextValue(
                                 prop.name));
             }
             if (fieldType.getTypeRoot() == DataTypeRoot.CHAR && v.length() != 1) {
-                throw new IllegalArgumentException(formattedMessage);
+                throw new IllegalArgumentException(
+                        charLengthExceptionMessage(prop.name, v.length()));
             }
             return v.charAt(0);
         }
@@ -211,6 +209,12 @@ private static Object convertTextValue(
                         prop.name));
     }
 
+    public static String charLengthExceptionMessage(String fieldName, int length) {
+        return String.format(
+                "Field %s expects exactly one character for CHAR type, got length %d.",
+                fieldName, length);
+    }
+
     /**
      * Converts a DECIMAL value from an InternalRow into a BigDecimal using the column's precision
      * and scale. The row position is assumed non-null (caller checks), so this never returns null.