[Java] add jdk migration doc (#715)

add migration doc

docs/guide/java_object_graph_guide.md

@@ -3,10 +3,10 @@ title: Java Object Graph Guide
 order: 0
 -- fury_frontmatter -->
 
-## Java object graph serialization
+# Java object graph serialization
 When only java object serialization needed, this mode will have better performance compared to cross-language object graph serialization.
 
-### Quick Start
+## Quick Start
 ```java
 import java.util.List;
 import java.util.Arrays;
@@ -54,7 +54,8 @@ public class Example {
 }
 ```
 
-### Advanced Fury Creation
+## Advanced Usage
+### Fury creation
 Single thread fury:
 ```java
 Fury fury = Fury.builder()
@@ -173,3 +174,15 @@ Object newObj = fury.execute(
 Fury support deserializing unexisted classes, this feature can be enabled by `FuryBuilder#withDeserializeUnExistClassEnabled(true)`. When enabled, and metadata sharing enabled, Fury will store the deserialized data of this type in a lazy subclass of Map. By using the lazy map implemented by Fury, the rebalance cost of filling map during deserialization can be avoided, which further improves performance. If this data is sent to another process and the class exists in this process, the data will be deserialized into the object of this type without losing any information.
 
 If metadata sharing is not enabled, the new class data will be skipped and a UnExistedSkipClass stub object will be returned.
+
+## Migration
+### JDK migration
+If you use jdk serialization before, and you can't upgrade your client and server at the same time, which is common for online application. Fury provided an util method `io.fury.serializer.JavaSerializer.serializedByJDK` to check whether the binary are generated by jdk serialization, you use following pattern to make exiting serialization protocol-aware, then upgrade serialization to fury in an async rolling-up way:
+```java
+if (JavaSerializer.serializedByJDK(bytes)) {
+  ObjectInputStream objectInputStream = xxx;
+  return objectInputStream.readObject();
+} else {
+  return fury.deserialize(bytes);
+}
+```