Add support for CharTagMapBuilder.withTagLengthSwap

Ability to change the order of Tag and Length tags.

jpos/src/main/java/org/jpos/tlv/CharTag.java

@@ -39,6 +39,8 @@ public class CharTag {
     private final String tagId;
     private final String value;
 
+    private boolean swapTagWithLength;
+
     /**
      * Internal Tag constructor.
      *
@@ -61,6 +63,15 @@ protected void setLengthSize(int size) {
         lengthSize = size;
     }
 
+    /**
+     * Swap tag with length.
+     *
+     * @param swap indicates if tag element will be swapped with length element
+     */
+    protected void withTagLengthSwap(boolean swap) {
+        swapTagWithLength = swap;
+    }
+
     /**
      * Form TLV for this tag.
      *
@@ -71,7 +82,13 @@ public String getTLV() {
         if (value != null)
             vLen = value.length();
 
-        String tlv = tagId + ISOUtil.zeropad(vLen, lengthSize);
+        String length = ISOUtil.zeropad(vLen, lengthSize);
+        String tlv;
+        if (swapTagWithLength)
+            tlv = length + tagId;
+        else
+            tlv = tagId + length;
+
         if (vLen == 0)
             return tlv;
 

jpos/src/main/java/org/jpos/tlv/CharTagMap.java

@@ -42,6 +42,8 @@ public class CharTagMap extends HashMap<String, CharTag> {
     private int tagLen = 0x02;
     private int lenLen = 0x03;
 
+    private boolean swapTagWithLength;
+
     /**
      * Creates new empty instance of text TLV tag map.
      * <p>
@@ -92,6 +94,15 @@ protected void setLengthSize(int size) throws IllegalArgumentException {
         lenLen = size;
     }
 
+    /**
+     * Sets size of length element.
+     *
+     * @param swap indicates if tag element will be swapped with length element
+     */
+    protected void withTagLengthSwap(boolean swap) {
+        swapTagWithLength = swap;
+    }
+
     /**
      * Unpack string to TLV tag map.
      *
@@ -159,6 +170,7 @@ public CharTag createTLV(String tagId, String value) throws IllegalArgumentExcep
 
         CharTag tag = new CharTag(tagId, value);
         tag.setLengthSize(lenLen);
+        tag.withTagLengthSwap(swapTagWithLength);
         return tag;
     }
 
@@ -218,8 +230,16 @@ private int stripLength(CharBuffer buffer) throws IllegalArgumentException {
     }
 
     private CharTag getTLVMsg(CharBuffer buffer) throws IllegalArgumentException {
-        String tagId = stripTagId(buffer);
-        int len = stripLength(buffer);
+        String tagId;
+        int len;
+        if (swapTagWithLength) {
+            len = stripLength(buffer);
+            tagId = stripTagId(buffer);
+        } else {
+            tagId = stripTagId(buffer);
+            len = stripLength(buffer);
+        }
+
         if (buffer.remaining() < len)
             throw new IllegalArgumentException(
                 String.format("%s tag '%s' length '%03d' exceeds available"

jpos/src/main/java/org/jpos/tlv/CharTagMapBuilder.java

@@ -19,7 +19,10 @@
 package org.jpos.tlv;
 
 /**
- * Builder to create TLV tag maps stored as sequence of characters.
+ * Builder to create TLV/LTV tag maps stored as sequence of characters.
+ * <p>
+ * Using {@code withTagLengthSwap(true)} while creating the builder causes
+ * switchs {@code CharTagMap} in LTV mode.
  *
  * @author Robert Demski <[email protected]>
  */
@@ -28,6 +31,8 @@ public class CharTagMapBuilder {
     protected Integer tagSize;
     protected Integer lengthSize;
 
+    protected boolean swapTagWithLength;
+
     /**
      * Constructs a new instance of the builder.
      */
@@ -57,6 +62,17 @@ public CharTagMapBuilder withTagSize(int size) {
         return this;
     }
 
+    /**
+     * Swap Tag with Length.
+     *
+     * @param swap indicates if tag element will be swapped with length element
+     * @return this, for chaining, not {@code null}
+     */
+    public CharTagMapBuilder withTagLengthSwap(boolean swap) {
+        swapTagWithLength = swap;
+        return this;
+    }
+
     /**
      * Completes this builder by creating the {@code CharTagMap}.
      *
@@ -71,6 +87,8 @@ public CharTagMap build() throws IllegalArgumentException {
         if (lengthSize != null)
             tm.setLengthSize(lengthSize);
 
+        tm.withTagLengthSwap(swapTagWithLength);
+
         return tm;
     }
 

jpos/src/test/java/org/jpos/tlv/CharTagMapBuilderTest.java

@@ -70,6 +70,23 @@ public void testBuild() {
         assertEquals("Foo Bar", tm.getTagValue("KV1"));
     }
 
+    @Test
+    public void testBuildSwapped() {
+        CharTagMap tm = instance
+                .withTagLengthSwap(true)
+                .build();
+
+        tm.unpack("019XYThe quick brown fox007KVFoo Bar");
+        assertEquals("The quick brown fox", tm.getTagValue("XY"));
+        assertEquals("Foo Bar", tm.getTagValue("KV"));
+
+        String result = tm.pack();
+        tm.clear();
+        tm.unpack(result);
+        assertEquals("The quick brown fox", tm.getTagValue("XY"));
+        assertEquals("Foo Bar", tm.getTagValue("KV"));
+    }
+
     @Test
     public void testBuildLongTagSize() {
         thrown = assertThrows(IllegalArgumentException.class,