SerializationException: Cannot deserialize

Q: Make the cached class implement Serializable

When to use: Use this if you are using the default JDK serializer.. Java serialization requires the class to implement `Serializable`. Add `implements Serializable` and a `serialVersionUID`.

Q: Configure GenericJackson2JsonRedisSerializer

When to use: Use this as the enterprise best practice.. Instead of brittle Java serialization, tell Spring Boot to serialize objects as JSON before storing them in Redis.

Q: Clear the Redis cache

When to use: Use this if you recently changed the class structure (added/removed fields).. Old bytes in Redis no longer match the new Java class. Flushing Redis forces a clean slate.

Q: Add serialVersionUID

When to use: Use this if you forgot to add it and the class evolved.. If you don't define a `serialVersionUID`, Java generates one based on the class structure. Changing the class changes the ID, breaking deserialization of old data.

Q: Ensure default constructor exists

When to use: Use this if using Jackson JSON serialization.. Jackson needs a default (no-args) constructor to instantiate the object before populating fields.

🔴 The Error You're Seeing

Confirm this matches your console output. If it does, you're in the right place.

ERROR LOG

2026-02-20 12:15:10.220 ERROR 8842 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.springframework.data.redis.serializer.SerializationException: Cannot deserialize; nested exception is org.springframework.core.serializer.support.SerializationFailedException: Failed to deserialize payload. Is the object a type supported by the serializer?] with root cause

org.springframework.data.redis.serializer.SerializationException: Cannot deserialize

⚡ Quick Fix Works 80% of the time

Make the cached object implement Serializable, or configure a JSON serializer.

public class User implements Serializable {
    private static final long serialVersionUID = 1L;
    // fields...
}

🧠 Why this Happens

Tap to expand the deep technical explanation

Spring Data Redis uses JDK serialization by default. It tried to convert the bytes stored in Redis back into a Java object, but failed. This happens if the Java class doesn't implement `Serializable`, lacks a `serialVersionUID`, or if you recently changed the class structure after caching the data.

The HITEC City Parking Spot Analogy:

It's like trying to open a locked safe with the wrong key. The safe (Redis) holds the data, but the key (Java serialization) doesn't match the lock, so it refuses to open.

🔁 How to Reproduce Confirm this is your error

Create a class that does NOT implement Serializable. Cache an instance in Redis using @Cacheable. Retrieve it. It will crash.

🛠️ Solutions (5 Ways to Fix)

Solution 1✓ Most common cause

Make the cached class implement Serializable

👉 Use this if you are using the default JDK serializer.

Java serialization requires the class to implement `Serializable`. Add `implements Serializable` and a `serialVersionUID`.

import java.io.Serializable;

public class User implements Serializable {
    private static final long serialVersionUID = 1L;
    private String name;
}

Solution 2

Configure GenericJackson2JsonRedisSerializer

👉 Use this as the enterprise best practice.

Instead of brittle Java serialization, tell Spring Boot to serialize objects as JSON before storing them in Redis.

@Bean
public RedisCacheConfiguration cacheConfiguration() {
    return RedisCacheConfiguration.defaultCacheConfig()
        .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer()));
}

Solution 3

Clear the Redis cache

👉 Use this if you recently changed the class structure (added/removed fields).

Old bytes in Redis no longer match the new Java class. Flushing Redis forces a clean slate.

# Connect to Redis CLI
redis-cli
# Flush all data
FLUSHALL

Solution 4

Add serialVersionUID

👉 Use this if you forgot to add it and the class evolved.

If you don't define a `serialVersionUID`, Java generates one based on the class structure. Changing the class changes the ID, breaking deserialization of old data.

private static final long serialVersionUID = 1L;

Solution 5

Ensure default constructor exists

👉 Use this if using Jackson JSON serialization.

Jackson needs a default (no-args) constructor to instantiate the object before populating fields.

public class User {
    public User() {} // Required for Jackson
    // ...
}

📋 Version Notes

Spring Boot 2.x

Uses JdkSerializationRedisSerializer by default.

Spring Boot 3.x

Uses JdkSerializationRedisSerializer by default, but auto-configuration heavily favors JSON serializers.

🛡️ How to Prevent This Next Time

Never use default JDK serialization for Redis in production. Always configure a JSON serializer (`GenericJackson2JsonRedisSerializer`).