Solving the Cannot Deserialize Issue in Java Spring: Handling Lists of Objects Properly

Learn how to resolve `Cannot deserialize value` errors in Java Spring applications when dealing with lists of objects. Discover the correct implementation techniques and the importance of hosting APIs that return correctly structured data.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Difficulty in deserializating list of object

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding and Resolving Deserialization Issues in Spring Applications

The Problem: Deserialization of BankingList

Description of the Error

In your Java Spring project, you've set up an API that returns a list of banking transactions, but instead of encapsulating that list within an object, it simply returns an array. This mismatch in expected data structures leads to deserialization errors, hindering your application's ability to function properly.

Example of the Situation

Here's a brief example of your current implementation that generates the error:

The BankingClient application has a getTrans method:

[[See Video to Reveal this Text or Code Snippet]]

This method returns a List of Banking objects as JSON.

The AccountClient application attempts to retrieve this list:

[[See Video to Reveal this Text or Code Snippet]]

Providing Solutions: How to Fix the Deserialization Issue

Solution 1: Change the API Return Type

One straightforward approach is to update the API in the BankingClient to return a BankingList, which holds the list of banking transactions.

Update the BankingClient API:

[[See Video to Reveal this Text or Code Snippet]]

This change aligns the structure with the BankingList expected by the AccountClient, removing the deserialization issue.

Solution 2: Using an Array as the Return Type

If you cannot modify the BankingClient code, you can directly use the array type in your AccountClient.

Adjust the return type in AccountClient:

[[See Video to Reveal this Text or Code Snippet]]

Solution 3: Deserialize Manually Using ObjectMapper

For more complex scenarios, you might want to leverage the ObjectMapper to manage deserialization manually.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By understanding the structure of the data returned by your APIs and ensuring consistency in the expected object types, you can resolve the common issue of deserialization errors in Java Spring applications effectively. Whether you update your API, change return types, or utilize manual deserialization strategies with ObjectMapper, these solutions can streamline your data processing and make your application run smoothly.

Adopting these best practices not only resolves current errors but also leads to more maintainable and cleaner code in your Java applications.