Spring Data MongoDB Package Refactor Tool

Author: Niccolò Caselli Date: 2025-07-30

A Node.js utility tool that migrates package names in MongoDB documents' _class fields used by Spring Data MongoDB for JSON deserialization during ORM operations.

Problem Statement

When you refactor your Java package structure in Spring Boot applications, existing MongoDB documents still contain the old package names in their _class field. This causes deserialization failures when Spring Data MongoDB tries to instantiate objects from the database.

For example, if you change your package from org.caselli.cognitiveworkflow to org.stdlab.sallma, existing documents in MongoDB will still have:

{
  "_id": "...",
  "_class": "org.caselli.cognitiveworkflow.User",
  "name": "John Doe"
}

This will cause Spring Data MongoDB to fail when trying to deserialize the document because it can't find the class org.caselli.cognitiveworkflow.User.

Solution

This tool automatically updates all _class fields in your MongoDB collections to use the new package prefix, ensuring seamless migration when you refactor your Java package structure.

Prerequisites

• Node.js (version 14 or higher)
• MongoDB instance (local or remote)
• Access to the MongoDB database you want to refactor

Installation

1. Clone or download this repository
2. Install dependencies:

npm install

Usage

node index.js <mongodb-uri> <old-package-prefix> <new-package-prefix>

Parameters

• mongodb-uri: The MongoDB connection string
• old-package-prefix: The current package prefix in your documents
• new-package-prefix: The new package prefix you want to use

Examples

node index.js "mongodb+srv://username:password@cluster.mongodb.net/mydb" "com.oldcompany.app" "com.newcompany.app"

How It Works

1. Connection: Connects to the specified MongoDB instance
2. Collection Discovery: Scans all collections in the database
3. Document Search: For each collection, finds documents with _class fields matching the old package prefix
4. Package Refactoring: Updates each document's _class field to use the new package prefix
5. Reporting: Provides detailed logging of the refactoring process

Example Output

Spring Data MongoDB Package Refactoring Parameters:
   MongoDB URI: mongodb://localhost:27017/mydb
   Old Java Package: org.caselli.cognitiveworkflow
   New Java Package: org.stdlab.sallma
   Target: _class fields used by Spring Data MongoDB for JSON deserialization

Connecting to MongoDB for Spring Data package refactoring...
Connected successfully
Found 3 collections

Scanning collection for Spring Data _class fields: users
   Found 5 Spring Data documents to refactor
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.User → org.stdlab.sallma.User
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.User → org.stdlab.sallma.User
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.User → org.stdlab.sallma.User
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.User → org.stdlab.sallma.User
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.User → org.stdlab.sallma.User

Scanning collection for Spring Data _class fields: orders
   SKIP: No Spring Data documents found with old package prefix

Scanning collection for Spring Data _class fields: products
   Found 2 Spring Data documents to refactor
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.Product → org.stdlab.sallma.Product
   SUCCESS: Refactored _class: org.caselli.cognitiveworkflow.Product → org.stdlab.sallma.Product

Spring Data package refactoring completed successfully!
Total Spring Data documents refactored: 7
Connection closed

Before and After Example

Before Refactoring

{
  "_id": ObjectId("..."),
  "_class": "org.caselli.cognitiveworkflow.User",
  "name": "John Doe",
  "email": "john@example.com"
}

After Refactoring

{
  "_id": ObjectId("..."),
  "_class": "org.stdlab.sallma.User",
  "name": "John Doe",
  "email": "john@example.com"
}

Important Notes

1. Backup First: Always backup your MongoDB database before running this tool
2. Test Environment: Test the tool on a copy of your production data first
3. Package Structure: Ensure your new package structure is already implemented in your Java code
4. Spring Data Classes: Make sure your Spring Data entity classes are updated to use the new package names

Troubleshooting

Common Issues

1. Connection Failed: Check your MongoDB URI and network connectivity
2. No Documents Found: Verify the old package prefix is correct
3. Permission Denied: Ensure your MongoDB user has read/write permissions
4. Invalid URI: Make sure the MongoDB URI follows the correct format

Error Messages

• ERROR: Invalid MongoDB URI format - Check your connection string
• ERROR: Package prefixes cannot be empty - Provide both old and new package prefixes
• ERROR: Failed to update Spring Data document - Check database permissions

Contributing

Feel free to submit issues and enhancement requests!

License

This project is open source and available under the MIT License.

Support

If you encounter any issues or have questions, please open an issue in the repository.