How to fix java.io.NotSerializableException?
The core workaround for encountering java.io.NotSerializableException is to ensure that all classes that need to be serialized implement the Serializable interface and check the serialization support of nested objects. 1. Add implements Serializable to the main class; 2. Ensure that the corresponding classes of custom fields in the class also implement Serializable; 3. Use transient to mark fields that do not need to be serialized; 4. Check the unserialized types in collections or nested objects; 5. Check which class does not implement the interface; 6. Consider replacing design for classes that cannot be modified, such as saving critical data or using serializable intermediate structures; 7. Consider using alternatives such as JSON, binary protocol or database storage to avoid problems. During troubleshooting, the object diagram should be checked layer by layer to find the root cause.
I encountered java.io.NotSerializableException
usually because you are trying to serialize an object that does not implement Serializable
interface. This problem is common when using Java's object serialization function, such as when transferring, caching, or saving object state on the network.

To solve it, the core approach is to ensure that all classes that need to be serialized correctly implement the Serializable
interface.
Ensure that the class implements the Serializable interface
This is the most common solution. If one of your class or its parent class does not implement Serializable
, this exception will be thrown during serialization.

practice:
- Add
implements Serializable
to your class - If there are fields with custom object types in the class, the corresponding classes of these fields must also implement
Serializable
public class User implements Serializable { private String name; private int age; // Constructor, getter, setter, etc.}
Note: If you do not want a field to be serialized, you can add the
transient
keyword to modify it.
Check for non-serialized types in collections or nested objects
Sometimes the problem does not occur in the main class itself, but it internally refers to other classes that do not support serialization. For example:
-
ArrayList
is used, but it contains the class you wrote yourself, and that class does not implementSerializable
- The class contains some third-party library objects, such as
Logger
,Connection
and other resource objects.
suggestion:
- Iterate through the entire object graph and check whether each nested object supports serialization
- If some fields do not need to be serialized, mark them out with
transient
- For classes that cannot modify the source code, consider changing the design, such as saving only key data instead of the entire object
Check out which category is wrong with the exception information positioning
The exception information will clearly tell you which category caused the problem, such as:
java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: com.example.MyClass
At this time you will know that com.example.MyClass
does not implement Serializable
.
Operation suggestions:
- Look at the lowest exception class name in the log
- Find the class and add
Serializable
interface - If this class is something you cannot modify (such as from a third-party library), you may want to consider storing or passing data in another way, such as just keeping its ID or converting it into a serializable intermediate structure
Consider whether serialization is really needed
Sometimes this problem occurs because of design misuse. Not all scenarios need to be serialized natively in Java.
Alternatives:
- Use JSON serialization (such as Jackson, Gson)
- Use binary protocols (such as Protobuf, Thrift)
- Direct serialization of objects is replaced by database storage or shared memory.
This not only avoids NotSerializableException
, but also improves compatibility and performance.
Basically that's it. Although it seems simple, it is easy to ignore a certain layer of nested objects in complex projects, so you must patiently view them layer by layer when troubleshooting.
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