How to Fix org.hibernate.AnnotationException: No identifier specified for entity in Spring Boot

Описание: Learn how to resolve the common Hibernate error, `org.hibernate.AnnotationException: No identifier specified for entity`, when working with Spring Boot and JPA.
---
This video is based on the question https://stackoverflow.com/q/66228804/ asked by the user 'Akif Esad' ( https://stackoverflow.com/u/15178570/ ) and on the answer https://stackoverflow.com/a/66228913/ provided by the user 'Simon Martinelli' ( https://stackoverflow.com/u/1045142/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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: How to fix org.hibernate.AnnotationException: No identifier specified for entity

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Solving the Hibernate Annotation Error: No Identifier Specified for Entity

When developing applications using Spring Boot, Hibernate, and JPA, developers occasionally stumble upon various exceptions. One notable issue many encounter is the org.hibernate.AnnotationException: No identifier specified for entity. This error can halt your application and prevent successful data manipulation. Luckily, this guide will clarify the cause of this error and how to resolve it efficiently.

Understanding the Problem

The org.hibernate.AnnotationException typically suggests that Hibernate can't find a unique identifier (or primary key) for an entity class. Each entity class signifies a database table's row, and for Hibernate to manage these entities correctly, they need to have a designated primary key.

In the example you're facing, the specific error is tied to the City class which doesn't have the required annotations to identify its primary key.

The Key Ingredients

To understand better, let’s discuss the components involved:

Entity Class: Represents a table in a database.

@ Entity Annotation: Marks a class as a Hibernate entity.

@ Id Annotation: Designates a field as the entity's identifier.

Typical Scenario

From the stack trace provided, we see the following line:

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

This message implies that the City entity lacks the necessary identifier setup.

How to Fix the Error

To solve the annotation exception, the missing @ Id annotation needs to be added to the City class. Below are the steps to implement the fix:

Step 1: Locate the Entity Class

First, open your City.java file, which is defined under the package:

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

Step 2: Add the @ Id Annotation

Within the City class, find the field that will serve as the unique identifier. This is usually a field like id.

You need to modify the existing piece of code that defines your id variable as follows:

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

Complete City Class Example

After making the changes, your City class should look like this:

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

Step 3: Validate the Application Properties

Also, ensure that your application properties (located in application.properties or application.yml) are correctly set to connect to your database. An example of this is shown below:

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

Step 4: Restart Your Application

After implementing the changes, restart your Spring Boot application. This will help Hibernate reassess the entity configurations and should eliminate the error.

Conclusion

By adding the @ Id annotation and defining your primary key, you ensure that Hibernate can uniquely identify each record within the City table. This resolution is crucial for the correct functioning of any entity in your JPA applications. So, be attentive to your entity annotations to maintain an error-free environment as you develop your applications!

Feel free to reach out if you have further questions or encounter new hurdles in your coding journey!