👐 Enable Validation for the Users Collection

In this exercise, you will explore the pre-written JSON validation schema for the users collection, run a script to apply it to the collection, and test the schema validation by inserting a document that does not match the schema.

Explore the JSON schema

🚀 NodeJS/Express

The JSON schema for the users collection is stored in the server/src/schema-validation/apply-schema.ts file. Open the file and examine the schema.

☕️ Java Spring Boot

JSON schema for the users collection:

const userSchema = {
    bsonType: 'object',
    required: ['name', 'isAdmin'],
    properties: {
        name: {
            bsonType: 'string',
            minLength: 5,
            description: 'must be a string and is required'
        },
        isAdmin: {
            bsonType: 'bool',
            description: 'must be a boolean and is required'
        }
    }
};

The schema defines the following constraints:

• The required fields are name and isAdmin.
• The name field must be a string with a minimum length of five characters.
• The isAdmin field must be a boolean.

Explore the script to apply the schema

🚀 NodeJS/Express

Examine the lines immediately following the schema definition in the apply-schema.ts file. You will see a function that applies the schema to the users collection.

console.log('Applying schema validation for users...');
const resultUsers = await db.command({
    collMod: 'users',
    validator: {
        $jsonSchema: userSchema
    },
    validationLevel: 'strict',
    validationAction: 'error'
});

The function uses the db.command() method to apply the schema to the users collection.

• The collMod option specifies the collection to which the schema should be applied.
• The validator option specifies the JSON schema to use for validation. This is the userSchema object declared just above.
• The validationLevel option specifies the level of validation to perform. This could be strict or moderate.
  • If you set it to strict, the document will be inserted and updated only if it passes validation.
  • If you set it to moderate, updates to existing documents in the collection that don't match the validation rules aren't checked for validity.
• And finally, the validationAction option specifies the action to take when a document fails validation. This could be error or warn.
  • If you set it to error, MongoDB rejects any insert or update that violates the validation criteria.
  • If you set it to warn, the operation proceeds, but the violation is recorded in the MongoDB log.

☕️ Java Spring Boot

In this step, we’ll review the code that applies schema validation to the users collection. It’s already implemented in SchemaValidationConfig.java no changes needed. We’ll look at two methods:

src/main/java/com/mongodb/devrel/library/infrastructure/config/SchemaValidationConfig.java

@Configuration
public class SchemaValidationConfig {

    // fields ..

    private void applyUserSchema(MongoDatabase db)  {
       // implementation
    }

    private void runCollMod(MongoDatabase db, String collection, Document schema) {
       // implementation
    }

}

• applyUserSchema(MongoDatabase db)

  • Ensures the users collection exists.
  • Builds a $jsonSchema requiring name (string, minLength: 5) and isAdmin (boolean).
  • Calls runCollMod(...) to attach the validator to the collection.

• runCollMod(MongoDatabase db, String collection, Document schema)

  • Executes collMod with validator, validationLevel=strict, and validationAction=error.

For readability, only the class structure is shown above. You can open the SchemaValidationConfig in your project to review the complete implementation.

Apply the schema to the users collection

🚀 NodeJS/Express

You need to run the script to apply the schema to the users collection.

1. Open a new terminal emulator tab in your GitHub codespace.

   1. Locate the bottom panel and click on the TERMINAL tab.
   2. Locate the + icon on the top right of the terminal panel and click on it to open a new terminal tab.
   3. Click on the new terminal tab to activate it.

2. Run the following command to apply the schema to the users collection:

   cd server
   npx tsx src/schema-validation/apply-schema.ts

   You might be prompted to allow pasting into the terminal. Click "Allow" to paste the command.

   Click "Enter" to run the command. After a few seconds, you should see the following output:

   Connecting to MongoDB Atlas...
   Connected!
   
   Applying schema validation for users...
   Schema validation enabled!

☕️ Java Spring Boot

The applyUserSchema method is triggered by the execute method, which runs only if the property lab.schema-mode is set. To apply the schema, you must set this property to apply.

Stop the application if it’s running and restart it with:

mvn spring-boot:run -Dspring-boot.run.jvmArguments="-Dlab.schema-mode=apply"

When the application starts, you should see a message confirming that the validator was successfully applied to the users collection:

Test the schema validation

🚀 NodeJS/Express

Now that the schema validation is enabled for the users collection, you can test it by inserting a document that does not match the schema.

1. Open the file server/src/schema-validation/test-validation.ts file.
2. Explore the call to the insertOne() function around line 12 that will try to insert a new user and the error handling code around line 18.
3. Execute the script by running the following command.

npx tsx src/schema-validation/test-validation.ts

The error describes that the name and isAdmin fields are required but missing in the document you tried to insert.

Modify the script to insert a document again with the name and isAdmin fields and you should see the document inserted successfully.

☕️ Java Spring Boot

In this step, the schema is already created, and it’s time to test it. The validateUserSchema method, already implemented, tries to insert a new user without the isAdmin field.

To trigger it, stop the application if it’s running and start it again with the property set to test:

mvn spring-boot:run -Dspring-boot.run.jvmArguments="-Dlab.schema-mode=test"

In the logs, you should see an error indicating that the insert was rejected by the validator:

Summary

In this exercise, you explored the JSON schema for the users collection, ran a script to apply the schema to the collection, and tested the schema validation by inserting a document that does not match the schema.

In the next exercise, you will enable schema validation for the authors collection.