From 686cdfdc871ed323b46761bc5a99d851cc2c4a26 Mon Sep 17 00:00:00 2001
From: chaokunyang <shawn.ck.yang@gmail.com>
Date: Fri, 6 Oct 2023 18:22:26 +0800
Subject: [PATCH] add autocast doc and tests

---
 java/fury-core/src/main/java/io/fury/Fury.java | 18 +++++++++++++++++-
 .../src/test/java/io/fury/FuryTest.java        | 15 +++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/java/fury-core/src/main/java/io/fury/Fury.java b/java/fury-core/src/main/java/io/fury/Fury.java
index 6c3fc0fb33..87b194aaf6 100644
--- a/java/fury-core/src/main/java/io/fury/Fury.java
+++ b/java/fury-core/src/main/java/io/fury/Fury.java
@@ -618,7 +618,23 @@ public long readLong(MemoryBuffer buffer) {
     return LongSerializer.readLong(buffer, longEncoding);
   }
 
-  /** Deserialize <code>obj</code> from a byte array. */
+  /**
+   * Deserialize <code>obj</code> from a byte array. Note declared result type must be a class or
+   * superclass/interface of the serialized object, otherwise a {@link ClassCastException} will be
+   * thrown.
+   *
+   * <p>For example, if you serialized an object of type `Integer`, then your declared deserialized
+   * type is `String`, the deserialization will just throw a {@link ClassCastException}.
+   *
+   * <pre>{@code
+   * byte[] bytes = fury.serialize(1);
+   * String o = fury.deserialize(bytes); // throw ClassCastException.
+   * }</pre>
+   *
+   * @param bytes serialized data.
+   * @param <T> result type of the data.
+   * @return deserialized object.
+   */
   public <T> T deserialize(byte[] bytes) {
     return deserialize(MemoryUtils.wrap(bytes), null);
   }
diff --git a/java/fury-core/src/test/java/io/fury/FuryTest.java b/java/fury-core/src/test/java/io/fury/FuryTest.java
index bcbd90bc72..5f24dd27a6 100644
--- a/java/fury-core/src/test/java/io/fury/FuryTest.java
+++ b/java/fury-core/src/test/java/io/fury/FuryTest.java
@@ -16,6 +16,7 @@
 
 package io.fury;
 
+import static io.fury.FuryTestBase.getJavaFury;
 import static org.testng.Assert.assertEquals;
 import static org.testng.Assert.assertNull;
 import static org.testng.Assert.assertThrows;
@@ -535,4 +536,18 @@ public void testJavaOutputStream() throws IOException {
       assertEquals(newObj, beanA);
     }
   }
+
+  @Test
+  public void testDeserializationAutotypeCast() {
+    Fury fury = getJavaFury();
+    byte[] bytes = fury.serialize(1);
+    Integer i = fury.deserialize(bytes);
+    Assert.assertEquals(i, 1);
+    Assert.assertThrows(
+        ClassCastException.class,
+        () -> {
+          String str = fury.deserialize(bytes);
+          System.out.println(str);
+        });
+  }
 }