Custom Validation in Mule 4 Using Mule SDK

Custom Validation in Mule

Validators are operations that validate the Mule Message without changing the message. Validators can produce these effects:

If the condition the validator demands is fulfilled, the flow continues, and the Mule Message remains the same.
If the condition the validator demands is not fulfilled, an error is thrown.

Today we will be creating a custom validation that will validate whether a currency is valid or not.

Prerequisites

Steps to Create Custom Validator

Create Project: Go to your project folder and run the Maven command to generate the project for the Mule validator extension. mvn org.mule.extensions:mule-extensions-archetype-maven-plugin:1.2.0:generate

> mvn org.mule.extensions:mule-extensions-archetype-maven-plugin:1.2.0:generate

[INFO] Scanning for projects...
[INFO] 
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO] 
[INFO] --- mule-extensions-archetype-maven-plugin:1.2.0:generate (default-cli) @ standalone-pom ---
* Enter the name of the extension (empty for default): 
Mule Currency Validator
* Enter the extension's groupId (empty for default): 
org.shyam.mule.extension
* Enter the extension's artifactId (empty for default): 
mule-currency-validator
* Enter the extension's version (empty for default): 
1.0.0
* Enter the extension's main package (empty for default): 
currency
[INFO] Generating project in Batch mode
[INFO] Archetype repository not defined. Using the one from [org.mule.extensions:mule-extensions-archetype:1.2.0] found in catalog remote
[INFO] ----------------------------------------------------------------------------
[INFO] Using following parameters for creating project from Archetype: mule-extensions-archetype:1.2.0
[INFO] ----------------------------------------------------------------------------
[INFO] Parameter: groupId, Value: mule-currency-validator
[INFO] Parameter: artifactId, Value: mule-currency-validator
[INFO] Parameter: version, Value: 1.0.0
[INFO] Parameter: package, Value: currency
[INFO] Parameter: packageInPathFormat, Value: currency
[INFO] Parameter: extensionNameNoSpaces, Value: Mulecurrencyvalidator
[INFO] Parameter: extensionName, Value: Mule-currency-validator
[INFO] Parameter: package, Value: currency
[INFO] Parameter: groupId, Value: mule-currency-validator
[INFO] Parameter: artifactId, Value: mule-currency-validator
[INFO] Parameter: version, Value: 1.0.0
[WARNING] Don't override file /Users/shyamrajprasad/mule/mule-currency-validator/src/main/java/currency
[WARNING] Don't override file /Users/shyamrajprasad/mule/mule-currency-validator/src/test/java/currency
[WARNING] Don't override file /Users/shyamrajprasad/mule/mule-currency-validator/src/test/resources
[INFO] Project created from Archetype in dir: /Users/shyamrajprasad/mule/mule-currency-validator
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  55.274 s
[INFO] Finished at: 2022-06-12T20:19:28+05:30
[INFO] ------------------------------------------------------------------------

Remove Connector Configurations: Delete the below four Java classes. These files will be used for the custom connectors.
- CurrencyValidatorConfiguration
- CurrencyValidatorConnection
- CurrencyValidatorConnectionProvider
- CurrencyValidatorOperationsTestCase
Currency Dependency: Add the below dependency in pom.xml for currency.

<dependencies>
    <dependency>
        <groupId>org.javamoney</groupId>
        <artifactId>moneta</artifactId>
        <version>1.1</version>
    </dependency>
</dependencies>

CurrencyValidatorExtension: This is a currency validator extension class. Add the below lines in this class.

@Xml(prefix = "currency-validator")
@Extension(name = "Currency Validator")
@ErrorTypes(CurrencyError.class)
@Operations(CurrencyValidatorOperations.class)
public class CurrencyValidatorExtension {

}

CurrencyValidatorOperations: The CurrencyValidatorOperations class below adds a validation method that is annotated with @Validator. The method throws an error type that comes from the generic validation error type. Note that you can also annotate the class CurrencyValidatorOperations with @Validator, but if you do, any other operations in it will be flagged as validators.

public class CurrencyValidatorOperations {

    @Validator
    @Throws(CurrencyErrorsProvider.class)
    public void isValidCurrencyCode(String currencyCode) throws Exception {
        Collection<CurrencyUnit> currencyUnits= Monetary.getCurrencies();
        Set<String> currencyCodes = new HashSet<String>();
        for (CurrencyUnit c : currencyUnits) {
            currencyCodes.add(c.getCurrencyCode());
        }

        if(!currencyCodes.contains(currencyCode)) {
            throw new ModuleException(CurrencyError.INVALID_CURRENCY_CODE, new IllegalArgumentException("Invalid currency : " + currencyCode));
        }
    }

}

CurrencyError: This creates the error to throw if the currency validation fails. Notice that it is named according to the validation failure.

public enum CurrencyError implements ErrorTypeDefinition<CurrencyError> {
    INVALID_CURRENCY_CODE(MuleErrors.VALIDATION);

    private ErrorTypeDefinition<? extends Enum<?>> parent;

    CurrencyError(ErrorTypeDefinition<? extends Enum<?>> parent) {
        this.parent = parent;
    }

    @Override
    public Optional<ErrorTypeDefinition<? extends Enum<?>>> getParent() {
        return Optional.ofNullable(parent);
    }
}

CurrencyErrorsProvider: The validator method needs a ErrorTypeProvider that knows all the error types that the validation can throw. This example creates a ErrorTypeProvider that says that the only error the method can throw is of type CURRENCY-VALIDATOR:INVALID_CURRENCY_CODE

public class CurrencyErrorsProvider implements ErrorTypeProvider {

    @Override
    public Set<ErrorTypeDefinition> getErrorTypes() {
        HashSet<ErrorTypeDefinition> errors = new HashSet<>();
        errors.add(CurrencyError.INVALID_CURRENCY_CODE);
        return errors;
    }
}

Validator Icon: Go to the project root directory and create an icon folder. Place an SVG file image in this folder, and the icon file name should be icon.svg.
Maven Build: Go to the project directory and run terminal. Run mvn clean install to build the project.

How To Use Custom Validators in Mule Application

Create a Mule Application: Go to Anypoint Studio and create a Mule application for testing the custom validation.
Add Custom Validator Mule Plugin: Go to pom.xml and add the dependency for the custom validator Mule plugin for currency. Make sure you have added the classifier as mule-plugin and the dependency information will come from the Mule SDK validator.

<dependency>
          <groupId>org.shyam</groupId>
          <artifactId>mule-currency-validator</artifactId>
          <version>1.0.1</version>
          <classifier>mule-plugin</classifier>
        </dependency>

HTTP Listener: Add an HTTP listener with default configuration in the testing Mule application.
Currency Validation: Drag the currency validation and pass the currency. We are reading the currency from query params.

    <currency-validator:is-valid-currency-code doc:name="Is valid currency code" doc:id="e9b8a803-ef0f-437e-b337-e33eb5cfc614" currencyCode="#[attributes.queryParams.currencyCode]"/>

Failed Validation Execution: Below are the error logs from the Mule application for invalid currency.

ERROR 2022-06-12 22:52:37,285 [[MuleRuntime].uber.01: [helloworldtesting].currencyValidatoFlow.CPU_LITE @398d10a9] [processor: currencyValidatoFlow/processors/0; event: 4132b1b0-ea74-11ec-bf77-f84d89960c47] org.mule.runtime.core.internal.exception.OnErrorPropagateHandler: 
********************************************************************************
Message               : Invalid currency : RUPEE
Element               : currencyValidatoFlow/processors/0 @ helloworldtesting:helloworldtesting.xml:48 (Is valid currency code)
Element DSL           : <currency-validator:is-valid-currency-code doc:name="Is valid currency code" doc:id="467879a6-8c4c-49be-93bd-f510a029e842" currencyCode="#[attributes.queryParams.currency]"></currency-validator:is-valid-currency-code>
Error type            : CURRENCY-VALIDATOR:INVALID_CURRENCY_CODE
FlowStack             : at currencyValidatoFlow(currencyValidatoFlow/processors/0 @ helloworldtesting:helloworldtesting.xml:48 (Is valid currency code))

  (set debug level logging or '-Dmule.verbose.exceptions=true' for everything)
********************************************************************************

Curl Command: curl --location --request GET 'localhost:8081/currency?currency=RUPEE'

Success Execution: If we pass the correct currency, we will get no validation error and response as currency INR. The curl command is: curl --location --request GET 'localhost:8081/currency?currency=INR'

Github Repository For Mule Custom Validation

https://github.com/shyamrajprasad/mule-currency-validator

Conclusion

Today we have learned how we can develop the Mule custom validation using Mule JAVA SDK. In a future tutorial, I will cover the Mule SDK for the REST API.

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