Troubleshooting Null Inserts in Your Spring Boot Application's MySQL Database

Fear not the nulls! Discover how to resolve issues with your Spring Boot application inserting null values into your MySQL database. Follow our step-by-step guide for a smoother coding experience.
---

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: Spring Boot application is inserting nulls into my mysql table

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Troubleshooting Null Inserts in Your Spring Boot Application's MySQL Database

When developing a Spring Boot application, one common issue that developers often face is the unexpected insertion of null values into their MySQL database. This can be particularly frustrating, as it may seem like everything is set up correctly, yet the data you tried to insert isn't being saved properly. In this guide, we'll explore a typical scenario where nulls are mistakenly inserted and provide a step-by-step guide to resolving the issue.

The Problem

Imagine you have set up a simple Spring Boot application that is supposed to handle department details, enabling you to insert and retrieve them from a MySQL database. However, when trying to insert a department record, you receive a response showing null values for all fields except the autogenerated department ID. Here’s a brief overview of the symptoms:

Postman Request: When you send a request to your endpoint with valid JSON data for a new department, the department ID is generated correctly, but the rest of the fields are null.

Eclipse Console Logs: Your console shows SQL commands being executed correctly, but the actual values being inserted are marked with ?, indicating that they were not read properly from your request.

Understanding the Cause

In this case, the root of the problem lies in a mismatch between the property names in your Department entity class and the JSON payload structure sent in the HTTP request. Here is what happened:

Your JSON payload sent to the endpoint has fields named name, address, and code.

However, your Department entity class has properties defined as deparmentName, deparmentAddress, and departmentCode.

These name discrepancies mean that when Spring tries to map the incoming JSON to your Department entity, it fails to recognize the fields, resulting in null values.

Solution: Fixing the Field Mismatch

Step 1: Modify Your JSON Payload

One quick fix would be to change your JSON payload to align with your entity fields:

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

However, a better approach is to use Data Transfer Objects (DTOs) to separate your API layer from your entity layer, providing a cleaner and more adaptable design.

Step 2: Create a DTO Class

You can define a DepartmentDTO class that represents the data structure you want for the incoming JSON request:

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

Step 3: Update the Entity Class as Necessary

Your Department entity can remain mostly unchanged but keep in mind its actual fields and names.

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

Step 4: Create a Mapper Class

Next, it’s useful to create a mapper to convert your DTO to your entity:

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

Step 5: Update the Controller

Finally, modify your controller to accept the DTO and utilize the mapper for conversions:

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

Conclusion

By separating your data models (entities) from your API data structures (DTOs), you not only resolve the immediate issue of null inserts but also adhere to best practices in software design. Using DTOs allows for clearer, more maintainable code that is easy to adapt in the future.

If you continue to experience issues or have further questions, feel free to explore other resources or ask for help within the developer community. Happy coding!