Data truncation: Data too long for column 'name'

Q: Add @Size validation to your DTO

When to use: Use this to prevent bad data from ever reaching the database layer.. By adding Bean Validation constraints, Spring will return a 400 Bad Request to the client instead of crashing with a 500 Database error.

Q: Change the column definition in the Entity

When to use: Use this if the user legitimately needs to input longer text.. Explicitly define the database column type (like VARCHAR(255) or TEXT) using the @Column annotation.

Q: Manually alter the database table

When to use: Use this if your database schema is out of sync with your Entity and you can't use ddl-auto=update.. Run an ALTER TABLE SQL command directly on your database to increase the column size.

🔴 The Error You're Seeing

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

ERROR LOG

2026-02-14 14:22:18.300 ERROR 8842 --- [nio-8080-exec-6] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.springframework.dao.DataIntegrityViolationException: could not execute statement; SQL [n/a]] with root cause

java.sql.SQLDataException: Data truncation: Data too long for column 'name' at row 1

⚡ Quick Fix Works 80% of the time

Add @Size(max = 50) to your DTO field to reject long strings before they hit the database.

public class UserRequest {
    @Size(max = 50, message = "Name must be less than 50 characters")
    private String name;
}

🧠 Why this Happens

Tap to expand the deep technical explanation

The client sent a string that was longer than the maximum allowed size for that specific database column (e.g., trying to save a 100-character string into a VARCHAR(50) column). The database rejected the insertion.

The HITEC City Parking Spot Analogy:

It is like trying to pour a liter of water into a shot glass. The glass (database column) can only hold so much, and the rest overflows or is rejected.

🔁 How to Reproduce Confirm this is your error

Insert a value longer than the column length (for example a 100-character name into a VARCHAR(50)) without @Size validation. The database throws Data truncation: Data too long for column.

🛠️ Solutions (3 Ways to Fix)

Solution 1✓ Most common cause

Add @Size validation to your DTO

👉 Use this to prevent bad data from ever reaching the database layer.

By adding Bean Validation constraints, Spring will return a 400 Bad Request to the client instead of crashing with a 500 Database error.

public class UserRequest {
    @NotBlank
    @Size(max = 50)
    private String name;
}

Solution 2

Change the column definition in the Entity

👉 Use this if the user legitimately needs to input longer text.

Explicitly define the database column type (like VARCHAR(255) or TEXT) using the @Column annotation.

@Entity
public class User {
    @Column(length = 255, nullable = false) // or columnDefinition = "TEXT"
    private String name;
}

Solution 3

Manually alter the database table

👉 Use this if your database schema is out of sync with your Entity and you can't use ddl-auto=update.

Run an ALTER TABLE SQL command directly on your database to increase the column size.

-- SQL Script
ALTER TABLE users MODIFY name VARCHAR(255);

📋 Version Notes

Spring Boot 2.x

Throws DataIntegrityViolationException wrapping the SQL error.

Spring Boot 3.x

Identical behavior, but may wrap it in Hibernate's jakarta.persistence.PersistenceException first.

🛡️ How to Prevent This Next Time

Always mirror your database constraints (like VARCHAR lengths) with @Size annotations in your Java DTOs.