Adds _serialized String and Externalizable methods

Author: egalpin

src/main/java/com/fasterxml/jackson/core/JsonPointer.java

@@ -1,6 +1,11 @@
 package com.fasterxml.jackson.core;
 
 import com.fasterxml.jackson.core.io.NumberInput;
+import java.io.Externalizable;
+import java.io.IOException;
+import java.io.ObjectInput;
+import java.io.ObjectOutput;
+import java.io.ObjectStreamException;
 
 /**
  * Implementation of
@@ -17,7 +22,7 @@
  *
  * @since 2.3
  */
-public class JsonPointer extends Serializable
+public class JsonPointer implements Externalizable
 {
     private static final long serialVersionUID = 1L; 
     /**
@@ -60,7 +65,11 @@ public class JsonPointer extends Serializable
      * so that {@link #toString} should be as efficient as possible.
      */
     protected final String _asString;
-    
+    /**
+     * Strictly used by serialization as an intermediate placeholder.
+     */
+    private String _serialized;
+
     protected final String _matchingPropertyName;
 
     protected final int _matchingElementIndex;
@@ -73,9 +82,10 @@ public class JsonPointer extends Serializable
 
     /**
      * Constructor used for creating "empty" instance, used to represent
-     * state that matches current node.
+     * state that matches current node. Note that this constructor must be public for
+     * implementing {@link Externalizable}.
      */
-    protected JsonPointer() {
+    public JsonPointer() {
         _nextSegment = null;
         _matchingPropertyName = "";
         _matchingElementIndex = -1;
@@ -644,4 +654,17 @@ private static void _appendEscape(StringBuilder sb, char c) {
         }
         sb.append(c);
     }
+
+    @Override
+    public void writeExternal(ObjectOutput out) throws IOException {
+        out.writeUTF(_asString);
+    }
+    private Object readResolve() throws ObjectStreamException {
+        return compile(_serialized);
+    }
+
+    @Override
+    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
+        _serialized = in.readUTF();
+    }
 }

src/test/java/com/fasterxml/jackson/core/TestJsonPointer.java

@@ -1,5 +1,12 @@
 package com.fasterxml.jackson.core;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+
 public class TestJsonPointer extends BaseTest
 {
     public void testSimplePath() throws Exception
@@ -228,4 +235,31 @@ public void testLongNumbers() throws Exception
         assertTrue(ptr.matches());
         assertNull(ptr.tail());
     }
+
+    private static <T extends Serializable> byte[] pickle(T obj)
+        throws IOException
+    {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        ObjectOutputStream oos = new ObjectOutputStream(baos);
+        oos.writeObject(obj);
+        oos.close();
+        return baos.toByteArray();
+    }
+
+    private static <T extends Serializable> T unpickle(byte[] b, Class<T> cl)
+        throws IOException, ClassNotFoundException
+    {
+        ByteArrayInputStream bais = new ByteArrayInputStream(b);
+        ObjectInputStream ois = new ObjectInputStream(bais);
+        Object o = ois.readObject();
+        return cl.cast(o);
+    }
+    public void testPointerSerialization() throws Exception {
+
+        final String INPUT = "/Image/15/name";
+        JsonPointer original = JsonPointer.compile(INPUT);
+        JsonPointer copy = unpickle(pickle(original), JsonPointer.class);
+        assertEquals(original, copy);
+
+    }
 }