QFJ-965 Fixed regression when using non-default charset (#218)

(cherry picked from commit dc264ad)

Author: amichair

quickfixj-core/src/main/java/org/quickfixj/CharsetSupport.java

@@ -29,6 +29,7 @@ public class CharsetSupport {
 
     private static String charset = getDefaultCharset();
     private static Charset charsetInstance = Charset.forName(charset);
+    private static boolean isStringEquivalent = isStringEquivalent(charsetInstance);
 
     public static String getDefaultCharset() {
         return "ISO-8859-1";
@@ -47,9 +48,20 @@ public static boolean isStringEquivalent(Charset charset) {
         return charset.equals(CHARSET_ISO_8859_1) || charset.equals(CHARSET_ASCII);
     }
 
+    /**
+     * Returns whether the current charset's byte representation of a string
+     * is equivalent (as unsigned values) to the string characters themselves.
+     *
+     * @return whether the charset encoding is string-equivalent
+     */
+    public static boolean isStringEquivalent() {
+        return isStringEquivalent;
+    }
+
     public static void setCharset(String charset) throws UnsupportedEncodingException {
         CharsetSupport.charset = validate(charset);
         CharsetSupport.charsetInstance = Charset.forName(charset);
+        CharsetSupport.isStringEquivalent = isStringEquivalent(charsetInstance);
     }
 
     public static String getCharset() {

quickfixj-core/src/main/java/quickfix/Message.java

@@ -142,8 +142,6 @@ protected Context initialValue() {
         }
     };
 
-    protected static boolean IS_STRING_EQUIVALENT = CharsetSupport.isStringEquivalent(CharsetSupport.getCharsetInstance());
-
     /**
      * Do not call this method concurrently while modifying the contents of the message.
      * This is likely to produce unexpected results or will fail with a ConcurrentModificationException
@@ -156,7 +154,7 @@ protected Context initialValue() {
     @Override
     public String toString() {
         Context context = stringContexts.get();
-        if (IS_STRING_EQUIVALENT) { // length & checksum can easily be calculated after message is built
+        if (CharsetSupport.isStringEquivalent()) { // length & checksum can easily be calculated after message is built
             header.setField(context.bodyLength);
             trailer.setField(context.checkSum);
         } else {
@@ -168,7 +166,7 @@ public String toString() {
             header.calculateString(stringBuilder, null, null);
             calculateString(stringBuilder, null, null);
             trailer.calculateString(stringBuilder, null, null);
-            if (IS_STRING_EQUIVALENT) {
+            if (CharsetSupport.isStringEquivalent()) {
                 setBodyLength(stringBuilder);
                 setChecksum(stringBuilder);
             }

quickfixj-core/src/test/java/quickfix/MessageTest.java

@@ -303,16 +303,14 @@ public void testEmbeddedMessage() throws Exception {
 
     private void doTestMessageWithEncodedField(String charset, String text) throws Exception {
         CharsetSupport.setCharset(charset);
-        NewOrderSingle order = createNewOrderSingle();
-        NewOrderSingle.IS_STRING_EQUIVALENT = CharsetSupport.isStringEquivalent(CharsetSupport.getCharsetInstance());
         try {
+            NewOrderSingle order = createNewOrderSingle();
             order.set(new EncodedTextLen(MessageUtils.length(CharsetSupport.getCharsetInstance(), text)));
             order.set(new EncodedText(text));
             final Message msg = new Message(order.toString(), DataDictionaryTest.getDictionary());
             assertEquals(charset + " encoded field", text, msg.getString(EncodedText.FIELD));
         } finally {
             CharsetSupport.setCharset(CharsetSupport.getDefaultCharset());
-            NewOrderSingle.IS_STRING_EQUIVALENT = CharsetSupport.isStringEquivalent(CharsetSupport.getCharsetInstance());
         }
     }