From 5026ea0e78a700445bfe6678f2259dbefb4c27f8 Mon Sep 17 00:00:00 2001
From: Nicholas Rahn <nick@transparentech.com>
Date: Thu, 25 Jun 2015 15:13:10 +0200
Subject: [PATCH] Support for getting the length of an array.

---
 .../com/jayway/jsonpath/internal/token/PathToken.java | 11 +++++++++++
 .../jsonpath/internal/token/PropertyPathToken.java    |  5 +++++
 .../java/com/jayway/jsonpath/JsonProviderTest.java    |  7 +++++++
 3 files changed, 23 insertions(+)

diff --git a/json-path/src/main/java/com/jayway/jsonpath/internal/token/PathToken.java b/json-path/src/main/java/com/jayway/jsonpath/internal/token/PathToken.java
index 720728a2..0ed13df8 100644
--- a/json-path/src/main/java/com/jayway/jsonpath/internal/token/PathToken.java
+++ b/json-path/src/main/java/com/jayway/jsonpath/internal/token/PathToken.java
@@ -128,6 +128,17 @@ public abstract class PathToken {
         }
     }
 
+    void handleArrayLength(String currentPath, Object model, EvaluationContextImpl ctx) {
+        String evalPath = currentPath + ".length";
+        PathRef pathRef = ctx.forUpdate() ? PathRef.create(model, "length") : PathRef.NO_OP;
+        Object evalHit = ctx.jsonProvider().length(model);
+        if (isLeaf()) {
+            ctx.addResult(evalPath, pathRef, evalHit);
+        } else {
+            next().evaluate(evalPath, pathRef, evalHit, ctx);
+        }
+    }
+
     PathToken prev(){
         return prev;
     }
diff --git a/json-path/src/main/java/com/jayway/jsonpath/internal/token/PropertyPathToken.java b/json-path/src/main/java/com/jayway/jsonpath/internal/token/PropertyPathToken.java
index f7824036..db3a00b5 100644
--- a/json-path/src/main/java/com/jayway/jsonpath/internal/token/PropertyPathToken.java
+++ b/json-path/src/main/java/com/jayway/jsonpath/internal/token/PropertyPathToken.java
@@ -38,6 +38,11 @@ public class PropertyPathToken extends PathToken {
     @Override
     public void evaluate(String currentPath, PathRef parent, Object model, EvaluationContextImpl ctx) {
         if (!ctx.jsonProvider().isMap(model)) {
+            // Special case handling of the 'length' property of arrays.
+            if (isLeaf() && ctx.jsonProvider().isArray(model) && properties.size() == 1 && properties.get(0).equals("length")) {
+                handleArrayLength(currentPath, model, ctx);
+                return;
+            }
             throw new PathNotFoundException("Property " + getPathFragment() + " not found in path " + currentPath);
         }
 
diff --git a/json-path/src/test/java/com/jayway/jsonpath/JsonProviderTest.java b/json-path/src/test/java/com/jayway/jsonpath/JsonProviderTest.java
index 9c80e56b..bb7504dc 100644
--- a/json-path/src/test/java/com/jayway/jsonpath/JsonProviderTest.java
+++ b/json-path/src/test/java/com/jayway/jsonpath/JsonProviderTest.java
@@ -75,6 +75,13 @@ public class JsonProviderTest extends BaseTest {
         assertThat(using(GSON_CONFIGURATION).parse(JSON).read("$", typeRef)).extracting("foo").containsExactly("foo0", "foo1", "foo2");
     }
 
+    @Test
+    public void length_of_array() {
+        assertThat(using(JACKSON_CONFIGURATION).parse(JSON_DOCUMENT).read("$.store.book.length", Integer.class)).isEqualTo(4);
+        assertThat(using(JACKSON_JSON_NODE_CONFIGURATION).parse(JSON_DOCUMENT).read("$.store.book.length", Integer.class)).isEqualTo(4);
+        assertThat(using(JSON_SMART_CONFIGURATION).parse(JSON_DOCUMENT).read("$.store.book.length", Integer.class)).isEqualTo(4);
+        assertThat(using(GSON_CONFIGURATION).parse(JSON_DOCUMENT).read("$.store.book.length", Integer.class)).isEqualTo(4);
+    }
 
     public static class FooBarBaz<T> {
         public T gen;