Fixed #18

release-notes/VERSION-2.x

@@ -6,6 +6,7 @@ Project: jackson-databind
 
 2.10.0 (not yet released)
 
+#18: Make `ObjectNode` and `ArrayNode` serializable
 #1675: Remove "impossible" `IOException` in `readTree()` and `readValue()` `ObjectMapper`
   methods which accept Strings
  (requested by matthew-pwnieexpress@github)

src/main/java/com/fasterxml/jackson/databind/node/ArrayNode.java

@@ -23,7 +23,10 @@
  */
 public class ArrayNode
     extends ContainerNode<ArrayNode>
+    implements java.io.Serializable // since 2.10
 {
+    private static final long serialVersionUID = 1L;
+
     private final List<JsonNode> _children;
 
     public ArrayNode(JsonNodeFactory nf) {
@@ -842,6 +845,17 @@ public int hashCode() {
         return _children.hashCode();
     }
 
+    /*
+    /**********************************************************
+    /* JDK Serialization support
+    /**********************************************************
+     */
+
+    // Simplest way is by using a helper
+    Object writeReplace() {
+        return NodeSerialization.from(this);
+    }
+
     /*
     /**********************************************************
     /* Internal methods (overridable)

src/main/java/com/fasterxml/jackson/databind/node/BaseJsonNode.java

@@ -17,7 +17,6 @@
  */
 public abstract class BaseJsonNode
     extends JsonNode
-    implements JsonSerializable
 {
     protected BaseJsonNode() { }
 

src/main/java/com/fasterxml/jackson/databind/node/ContainerNode.java

@@ -26,6 +26,8 @@ protected ContainerNode(JsonNodeFactory nc) {
         _nodeFactory = nc;
     }
 
+    protected ContainerNode() { _nodeFactory = null; } // only for JDK ser
+
     // all containers are mutable: can't define:
 //    @Override public abstract <T extends JsonNode> T deepCopy();
 

src/main/java/com/fasterxml/jackson/databind/node/InternalNodeMapper.java

@@ -3,6 +3,7 @@
 import java.io.IOException;
 
 import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectReader;
 import com.fasterxml.jackson.databind.ObjectWriter;
 import com.fasterxml.jackson.databind.json.JsonMapper;
 
@@ -15,10 +16,15 @@
  */
 final class InternalNodeMapper {
     private final static JsonMapper JSON_MAPPER = new JsonMapper();
+
     private final static ObjectWriter STD_WRITER = JSON_MAPPER.writer();
     private final static ObjectWriter PRETTY_WRITER = JSON_MAPPER.writer()
             .withDefaultPrettyPrinter();
 
+    private final static ObjectReader NODE_READER = JSON_MAPPER.readerFor(JsonNode.class);
+
+    // // // Methods for `JsonNode.toString()` and `JsonNode.toPrettyString()`
+
     public static String nodeToString(JsonNode n) {
         try {
             return STD_WRITER.writeValueAsString(n);
@@ -34,4 +40,14 @@ public static String nodeToPrettyString(JsonNode n) {
             throw new RuntimeException(e);
         }
     }
+
+    // // // Methods for JDK serialization support of JsonNodes
+
+    public static byte[] valueToBytes(Object value) throws IOException {
+        return JSON_MAPPER.writeValueAsBytes(value);
+    }
+
+    public static JsonNode bytesToNode(byte[] json) throws IOException {
+        return NODE_READER.readValue(json);
+    }
 }

src/main/java/com/fasterxml/jackson/databind/node/NodeSerialization.java

@@ -0,0 +1,32 @@
+package com.fasterxml.jackson.databind.node;
+
+import java.io.IOException;
+
+/**
+ * Helper value class only used during JDK serialization: contains JSON as `byte[]`
+ *
+ * @since 2.10
+ */
+class NodeSerialization implements java.io.Serializable {
+    private static final long serialVersionUID = 1L;
+
+    public byte[] json;
+
+    public NodeSerialization(byte[] b) { json = b; }
+
+    protected Object readResolve() {
+        try {
+            return InternalNodeMapper.bytesToNode(json);
+        } catch (IOException e) {
+            throw new IllegalArgumentException("Failed to JDK deserialize `JsonNode` value: "+e.getMessage(), e);
+        }
+    }    
+
+    public static NodeSerialization from(Object o) {
+        try {
+            return new NodeSerialization(InternalNodeMapper.valueToBytes(o));
+        } catch (IOException e) {
+            throw new IllegalArgumentException("Failed to JDK serialize `"+o.getClass().getSimpleName()+"` value: "+e.getMessage(), e);
+        }
+    }
+}

src/main/java/com/fasterxml/jackson/databind/node/ObjectNode.java

@@ -1,24 +1,27 @@
 package com.fasterxml.jackson.databind.node;
 
+import java.io.*;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.util.*;
+
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.type.WritableTypeId;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
 import com.fasterxml.jackson.databind.util.RawValue;
 
-import java.io.IOException;
-import java.math.BigDecimal;
-import java.math.BigInteger;
-import java.util.*;
-
 /**
  * Node that maps to JSON Object structures in JSON content.
  *<p>
  * Note: class was <code>final</code> temporarily for Jackson 2.2.
  */
 public class ObjectNode
     extends ContainerNode<ObjectNode>
+    implements java.io.Serializable
 {
+    private static final long serialVersionUID = 1L; // since 2.10
+
     // Note: LinkedHashMap for backwards compatibility
     protected final Map<String, JsonNode> _children;
 
@@ -872,6 +875,17 @@ public int hashCode()
         return _children.hashCode();
     }
 
+    /*
+    /**********************************************************
+    /* JDK Serialization support
+    /**********************************************************
+     */
+
+    // Simplest way is by using a helper
+    Object writeReplace() {
+        return NodeSerialization.from(this);
+    }
+
     /*
     /**********************************************************
     /* Internal methods (overridable)

src/test/java/com/fasterxml/jackson/databind/TestJDKSerialization.java

@@ -5,12 +5,6 @@
 
 import com.fasterxml.jackson.annotation.JsonAnyGetter;
 import com.fasterxml.jackson.annotation.JsonAnySetter;
-import com.fasterxml.jackson.databind.DeserializationConfig;
-import com.fasterxml.jackson.databind.JavaType;
-import com.fasterxml.jackson.databind.ObjectMapper;
-import com.fasterxml.jackson.databind.ObjectReader;
-import com.fasterxml.jackson.databind.ObjectWriter;
-import com.fasterxml.jackson.databind.SerializationConfig;
 import com.fasterxml.jackson.databind.type.TypeFactory;
 import com.fasterxml.jackson.databind.util.LRUMap;
 

src/test/java/com/fasterxml/jackson/databind/TestNodeJDKSerialization.java

@@ -0,0 +1,75 @@
+package com.fasterxml.jackson.databind;
+
+import java.io.*;
+
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+public class TestNodeJDKSerialization extends BaseMapTest
+{
+    private final ObjectMapper MAPPER = newObjectMapper();
+
+    /*
+    /**********************************************************
+    /* Then something bit different; serialize `JsonNode`(s)
+    /**********************************************************
+     */
+
+    // [databind#18]: Allow JDK serialization of `ObjectNode`
+    public void testObjectNodeSerialization() throws Exception
+    {
+        ObjectNode root = MAPPER.createObjectNode();
+        root.put("answer", 42);
+        ArrayNode arr = root.withArray("matrix");
+        arr.add(1).add(12345678901L).add(true).add("...");
+        ObjectNode misc = root.with("misc");
+        misc.put("value", 0.25);
+
+        byte[] ser = jdkSerialize(root);
+        JsonNode result = jdkDeserialize(ser);
+        assertEquals(root, result);
+    }
+
+    // [databind#18]: Allow JDK serialization of `ArrayNode`
+    public void testArrayNodeSerialization() throws Exception
+    {
+        ArrayNode root = MAPPER.createArrayNode();
+        root.add(false);
+        ObjectNode props = root.addObject();
+        props.put("answer", 42);
+        root.add(137);
+
+        byte[] ser = jdkSerialize(root);
+        JsonNode result = jdkDeserialize(ser);
+        assertEquals(root, result);
+    }
+
+    /*
+    /**********************************************************
+    /* Helper methods
+    /**********************************************************
+     */
+
+    protected byte[] jdkSerialize(Object o) throws IOException
+    {
+        ByteArrayOutputStream bytes = new ByteArrayOutputStream(1000);
+        ObjectOutputStream obOut = new ObjectOutputStream(bytes);
+        obOut.writeObject(o);
+        obOut.close();
+        return bytes.toByteArray();
+    }
+
+    @SuppressWarnings("unchecked")
+    protected <T> T jdkDeserialize(byte[] raw) throws IOException
+    {
+        ObjectInputStream objIn = new ObjectInputStream(new ByteArrayInputStream(raw));
+        try {
+            return (T) objIn.readObject();
+        } catch (ClassNotFoundException e) {
+            fail("Missing class: "+e.getMessage());
+            return null;
+        } finally {
+            objIn.close();
+        }
+    }
+}