[Java][Doc] enable requireClassRegistration in example by default (#1250

)

<!--
Thank you for your contribution!

Please review https://github.com/alipay/fury/blob/main/CONTRIBUTING.rst
before opening a pull request.
-->

## What do these changes do?
Disable class registration is dangerouse, we should enable class
registration by default even in doc.

<!-- Please give a short brief about these changes. -->

## Related issue number

<!-- Are there any issues opened that will be resolved by merging this
change? -->
Closes #xxxx

## Check code requirements

- [ ] tests added / passed (if needed)
- [ ] Ensure all linting tests pass, see
[here](https://github.com/alipay/fury/blob/main/CONTRIBUTING.rst) for
how to run them

README.md

@@ -161,7 +161,7 @@ public class Example {
       Fury fury = Fury.builder().withLanguage(Language.JAVA)
         // Allow to deserialize objects unknown types, more flexible 
         // but may be insecure if the classes contains malicious code.
-        .requireClassRegistration(false)
+        .requireClassRegistration(true)
         .build();
       // Registering types can reduce class name serialization overhead, but not mandatory.
       // If class registration enabled, all custom types must be registered.
@@ -173,7 +173,7 @@ public class Example {
       ThreadSafeFury fury = Fury.builder().withLanguage(Language.JAVA)
         // Allow to deserialize objects unknown types, more flexible 
         // but may be insecure if the classes contains malicious code.
-        .requireClassRegistration(false)
+        .requireClassRegistration(true)
         .buildThreadSafeFury();
       byte[] bytes = fury.serialize(object);
       System.out.println(fury.deserialize(bytes));

docs/guide/java_object_graph_guide.md

@@ -31,7 +31,7 @@ public class Example {
     Fury fury = Fury.builder().withLanguage(Language.JAVA)
       // Allow to deserialize objects unknown types, more flexible 
       // but may be insecure if the classes contains malicious code.
-      .requireClassRegistration(false)
+      .requireClassRegistration(true)
       .build();
     // Registering types can reduce class name serialization overhead, but not mandatory.
     // If class registration enabled, all custom types must be registered.
@@ -82,7 +82,7 @@ public class Example {
   private static final ThreadSafeFury fury = Fury.builder()
     // Allow to deserialize objects unknown types, more flexible 
     // but may be insecure if the classes contains malicious code.
-    .requireClassRegistration(false)
+    .requireClassRegistration(true)
     .buildThreadSafeFury();
 
   public static void main(String[] args) {
@@ -253,7 +253,7 @@ fury.getClassResolver().setClassChecker((classResolver, className) -> className.
 ```java
 AllowListChecker checker = new AllowListChecker(AllowListChecker.CheckLevel.STRICT);
 ThreadSafeFury fury = new ThreadLocalFury(classLoader -> {
-  Fury f = Fury.builder().requireClassRegistration(false).withClassLoader(classLoader).build();
+  Fury f = Fury.builder().requireClassRegistration(true).withClassLoader(classLoader).build();
   f.getClassResolver().setClassChecker(checker);
   checker.addListener(f.getClassResolver());
   return f;

docs/guide/scala_guide.md

@@ -23,15 +23,18 @@ When using fury for scala serialization, you should create fury at least with fo
 ```scala
 val fury = Fury.builder()
   .withScalaOptimizationEnabled(true)
-  .requireClassRegistration(false)
+  .requireClassRegistration(true)
   .withRefTracking(true)
   .build()
 ```
-Otherwise if you serialize some scala types such as `collection/Enumeration`, you will need to register some scala internal types:
+Depending on the object types you serialize, you may need to register some scala internal types:
 ```scala
 fury.register(Class.forName("scala.collection.generic.DefaultSerializationProxy"))
 fury.register(Class.forName("scala.Enumeration.Val"))
 ```
+If you want to avoid such registration, you can disable class registration by `FuryBuilder#requireClassRegistration(false)`.
+Note that this option allow to deserialize objects unknown types, more flexible but may be insecure if the classes contains malicious code.
+
 And circular references are common in scala, `Reference tracking` should be enabled by `FuryBuilder#withRefTracking(true)`. If you don't enable reference tracking, [StackOverflowError](https://github.com/alipay/fury/issues/1032) may happen for some scala versions when serializing scala Enumeration.
 
 Note that fury instance should be shared between multiple serialization, the creation of fury instance is not cheap.