[jackson-annotations] 158/207: API for custom Object Identifier resolution.

[Timo Aaltonen]

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tjaalton pushed a commit to branch master
in repository jackson-annotations.

commit f3cbf27e7176fd71b5e06ed07dc1ef6a963fb2c8
Author: Pascal Gélinas <pascal.gelinas at nuecho.com>
Date:   Wed Feb 5 17:29:00 2014 -0500

    API for custom Object Identifier resolution.
---
 .../jackson/annotation/JsonIdentityInfo.java       |  9 ++++
 .../jackson/annotation/ObjectIdGenerator.java      |  6 +--
 .../jackson/annotation/ObjectIdResolver.java       | 61 ++++++++++++++++++++++
 .../jackson/annotation/SimpleObjectIdResolver.java | 43 +++++++++++++++
 4 files changed, 116 insertions(+), 3 deletions(-)

diff --git a/src/main/java/com/fasterxml/jackson/annotation/JsonIdentityInfo.java b/src/main/java/com/fasterxml/jackson/annotation/JsonIdentityInfo.java
index 9ccde66..aa37216 100644
--- a/src/main/java/com/fasterxml/jackson/annotation/JsonIdentityInfo.java
+++ b/src/main/java/com/fasterxml/jackson/annotation/JsonIdentityInfo.java
@@ -60,6 +60,15 @@ public @interface JsonIdentityInfo
     public Class<? extends ObjectIdGenerator<?>> generator();
 
     /**
+     * Resolver to use for producing POJO from Object Identifier.
+     * <p>
+     * Default value is {@link SimpleObjectIdResolver}
+     * 
+     * @since 2.4
+     */
+    public Class<? extends ObjectIdResolver> resolver() default SimpleObjectIdResolver.class;
+
+    /**
      * Scope is used to define applicability of an Object Id: all ids
      * must be unique within their scope; where scope is defined
      * as combination of this value and generator type.
diff --git a/src/main/java/com/fasterxml/jackson/annotation/ObjectIdGenerator.java b/src/main/java/com/fasterxml/jackson/annotation/ObjectIdGenerator.java
index ce7ec69..b426562 100644
--- a/src/main/java/com/fasterxml/jackson/annotation/ObjectIdGenerator.java
+++ b/src/main/java/com/fasterxml/jackson/annotation/ObjectIdGenerator.java
@@ -100,17 +100,17 @@ public abstract class ObjectIdGenerator<T>
         /**
          * Type of {@link ObjectIdGenerator} used for generating Object Id
          */
-        private final Class<?> type;
+        public final Class<?> type;
 
         /**
          * Scope of the Object Id (may be null, to denote global)
          */
-        private final Class<?> scope;
+        public final Class<?> scope;
 
         /**
          * Object for which Object Id was generated: can NOT be null.
          */
-        private final Object key;
+        public final Object key;
 
         /**
          * Hash code
diff --git a/src/main/java/com/fasterxml/jackson/annotation/ObjectIdResolver.java b/src/main/java/com/fasterxml/jackson/annotation/ObjectIdResolver.java
new file mode 100644
index 0000000..afbb0b6
--- /dev/null
+++ b/src/main/java/com/fasterxml/jackson/annotation/ObjectIdResolver.java
@@ -0,0 +1,61 @@
+package com.fasterxml.jackson.annotation;
+
+import com.fasterxml.jackson.annotation.ObjectIdGenerator.IdKey;
+
+/**
+ * Definition of API used for constructing POJO from Object Identifiers (as
+ * annotated using {@link JsonIdentityInfo}).
+ * 
+ * @since 2.4
+ */
+public interface ObjectIdResolver {
+    /**
+     * Method called when a POJO is deserialized and has an Object Identifier.
+     * Method exists so that implementation can keep track of existing object in
+     * json stream that could be useful for further resolution.
+     * 
+     * @param id
+     *            The Object Identifer
+     * @param ob
+     *            The POJO associated to that Identifier
+     */
+    void bindItem(IdKey id, Object pojo);
+
+    /**
+     * Method called when deserialization encounters the given Object Identifier
+     * and requires the POJO associated with it.
+     * 
+     * @param id
+     *            The Object Identifier
+     * @return The POJO, or null if unable to resolve.
+     */
+    Object resolveId(IdKey id);
+
+    /**
+     * Factory method called to create a new instance to use for
+     * deserialization: needed since resolvers may have state (a pool of
+     * objects).
+     * <p>
+     * Note that actual type of 'context' is
+     * <code>com.fasterxml.jackson.databind.DeserializationContext</code>, but
+     * can not be declared here as type itself (as well as call to this object)
+     * comes from databind package.
+     * 
+     * @param context
+     *            Deserialization context object used (of type
+     *            <code>com.fasterxml.jackson.databind.DeserializationContext</code>
+     *            ; may be needed by more complex resolvers to access contextual
+     *            information such as configuration.
+     */
+    ObjectIdResolver newForDeserialization(Object context);
+
+    /**
+     * Method called to check whether this resolver instance can be used for
+     * Object Ids of specific resolver type; determination is based by passing a
+     * configured "blueprint" (prototype) instance; from which the actual
+     * instances are created (using {@link #newForDeserialization}).
+     * 
+     * @return True if this instance can be used as-is; false if not
+     */
+    boolean canUseFor(ObjectIdResolver resolverType);
+}
diff --git a/src/main/java/com/fasterxml/jackson/annotation/SimpleObjectIdResolver.java b/src/main/java/com/fasterxml/jackson/annotation/SimpleObjectIdResolver.java
new file mode 100644
index 0000000..b383ddd
--- /dev/null
+++ b/src/main/java/com/fasterxml/jackson/annotation/SimpleObjectIdResolver.java
@@ -0,0 +1,43 @@
+package com.fasterxml.jackson.annotation;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import com.fasterxml.jackson.annotation.ObjectIdGenerator.IdKey;
+
+/**
+ * Simple implementation of {@link ObjectIdResolver}
+ * 
+ * @author Pascal Gélinas
+ */
+public class SimpleObjectIdResolver implements ObjectIdResolver {
+    private Map<IdKey,Object> _items = new HashMap<ObjectIdGenerator.IdKey,Object>();
+
+    @Override
+    public void bindItem(IdKey id, Object ob)
+    {
+        if (_items.containsKey(id)) {
+            throw new IllegalStateException("Already had POJO for id (" + id.key.getClass().getName() + ") [" + id
+                    + "]");
+        }
+        _items.put(id, ob);
+    }
+
+    @Override
+    public Object resolveId(IdKey id)
+    {
+        return _items.get(id);
+    }
+
+    @Override
+    public boolean canUseFor(ObjectIdResolver resolverType)
+    {
+        return resolverType.getClass() == getClass();
+    }
+    
+    @Override
+    public ObjectIdResolver newForDeserialization(Object context)
+    {
+        return this;
+    }
+}

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