There are two types of extensions you can create:

• Custom handlebar helpers. Simple, for basic usage. These extensions can be used to transform or generate dynamically the response content.
• Custom response transformers for HTTP and JMS. Complex, for advanced usage. These extensions can do advanced transformations, routing of responses, and many more.

Traffic Parrot allows for Handlebars notation in the responses. They are typically used to add dynamic content to the responses. They can be used for both HTTP and JMS.

For example, all of these existing extensions are handlebar helpers:

• Load CSV data file
• Generate random values
• Handlebars extension functions
• And many more...

If you would like to add new Handlebars Helpers, have a look at the following example:

1. Download and open the SDK workspace project in an IDE like IntelliJ IDEA or Eclipse
2. Explore the project and the Java classes available in the SDK. Look for usages of TrafficParrotHelper They provide example usages of Handlebars Helpers. Have a look at both main and test classes.
3. Create a new extension class based on the examples provided in the SDK (by extending TrafficParrotHelper class). For example:

   package com.trafficparrot.sdk.example.http.template;
   
   import com.github.jknack.handlebars.Handlebars;
   import com.github.jknack.handlebars.Options;
   import com.trafficparrot.sdk.handlebars.TrafficParrotHelper;
   
   import java.io.IOException;
   import java.util.Random;
   
   public class RandomInteger extends TrafficParrotHelper<Object> {
       @Override
       public Handlebars.SafeString doApply(Object context, Options options) throws IOException {
           return new Handlebars.SafeString(String.valueOf(new Random().nextInt()));
       }
   }

4. Build the project ./mvnw clean install
5. Copy target/trafficparrot-sdk-workspace-x.y.z.jar
   to directory trafficparrot-enterprise-release-x.y.z/lib/virtualservice-x.y.z to use with HTTP
   or to directory trafficparrot-enterprise-release-x.y.z/lib/external to use with JMS
6. Look for properties trafficparrot.http.handlebars.helpers and trafficparrot.jms.handlebars.helpers in trafficparrot.properties and add your new class to the list of extension classes there. (Why do I have to edit the extensions properties every time?)
7. Stop Traffic Parrot
8. Start Traffic Parrot
9. If the name of the class you have created is RandomInteger the extension you will use in response templates will be called {{randomInteger}} by default. The name can be changed by implementing the TrafficParrotHelper.getName method.
10. Edit an existing mapping and put {{randomInteger}} anywhere in the response body.
11. Make a request to the virtual service
12. The response you receive should contain the randomly generated integer.

Traffic Parrot allows for creating custom HTTP response transformers. They allow for altering any part of the HTTP response in any way you like, and have access to the request data.

If you would like to add a new HTTP response transformer, have a look at the following example:

1. Download and open the SDK workspace project in an IDE like IntelliJ IDEA or Eclipse
2. Explore the project and the Java classes available in the SDK. They provide example usages of HTTP response transformers. Look for usages of HttpResponseTransformer and HttpResponseDefinitionTransformer. Have a look at both main and test classes.
3. Create a new extension class based on the examples provided in the SDK (by extending HttpResponseTransformer class). For example:

   package com.trafficparrot.sdk.example.http.responsetransformer;
   
   import com.github.tomakehurst.wiremock.common.FileSource;
   import com.github.tomakehurst.wiremock.extension.Parameters;
   import com.github.tomakehurst.wiremock.http.Request;
   import com.github.tomakehurst.wiremock.http.Response;
   import com.trafficparrot.sdk.http.HttpResponseTransformer;
   
   import java.util.Random;
   
   import static com.github.tomakehurst.wiremock.http.HttpHeaders.noHeaders;
   
   public class RandomServerFailure extends HttpResponseTransformer {
       @Override
       protected Response doTransform(Request request, Response response, FileSource fileSource, Parameters parameters) {
           if (new Random().nextBoolean()) {
               return Response.Builder
                       .like(response)
                       .but()
                       .status(500)
                       .headers(noHeaders())
                       .body("Server error!")
                       .build();
           } else {
               return response;
           }
       }
   
       @Override
       public String getName() {
           return getClass().getSimpleName();
       }
   }

4. Build the project ./mvnw clean install
5. Copy target/trafficparrot-sdk-workspace-x.y.z.jar to directory trafficparrot-enterprise-release-x.y.z/lib/virtualservice-x.y.z
6. Look for property trafficparrot.http.responsetransformers in trafficparrot.properties and add your new class to the list of extension classes there. (Why do I have to edit the extensions properties every time?)
7. Stop Traffic Parrot
8. Start Traffic Parrot
9. If the name of the class you have created is RandomServerFailure the extension you will use in response templates will be automatically called {{randomServerFailure}}
10. Edit an existing mapping and put {{randomServerFailure}} anywhere in the response body.
11. Make a few requests to the virtual service
12. The response you receive should randomly fail, as defined in the response transformer RandomServerFailure.

Traffic Parrot allows for creating custom JMS response transformers. They allow for altering any part of the JMS response message in any way you like, and have access to the request data.

If you would like to add a new JMS response transformer, have a look at the following example:

1. Download and open the SDK workspace project in an IDE like IntelliJ IDEA or Eclipse
2. Explore the project and the Java classes available in the SDK. They provide example usages of JMS response transformers. Look for usages of JmsResponseTransformer and TextJmsResponseTransformer. Have a look at both main and test classes.
3. Create a new extension class based on the examples provided in the SDK (by extending TextJmsResponseTransformer class). For example:

   package com.trafficparrot.sdk.example.jms;
   
   import com.github.tomakehurst.wiremock.common.Json;
   import com.trafficparrot.sdk.jms.Destination;
   import com.trafficparrot.sdk.jms.JmsResponse;
   import com.trafficparrot.sdk.jms.JmsResponseBuilder;
   import com.trafficparrot.sdk.jms.TextJmsResponseTransformer;
   
   import javax.jms.JMSException;
   import javax.jms.TextMessage;
   
   public class ChooseResponseQueueBasedOnRequestMessageBody extends TextJmsResponseTransformer {
       @Override
       protected JmsResponse doTransform(Destination requestDestination, TextMessage requestMessage, JmsResponse response) throws JMSException {
           Req payment = Json.read(requestMessage.getText(), Req.class);
           String newDestinationName;
           if ("foo".equals(payment.requestField)) {
               newDestinationName = "response_queue_1";
           } else if ("bar".equals(payment.requestField)) {
               newDestinationName = "response_queue_2";
           } else {
               logger.error("Destination not configured for req.requestField '" + payment.requestField + "'");
               throw new UnsupportedOperationException(payment.requestField);
           }
           logger.info("Redirecting message to " + newDestinationName);
   
           return new JmsResponseBuilder()
                   .like(response)
                   .withDestination(new Destination(newDestinationName, response.destination.type))
                   .build();
       }
   }
   
   class Req {
       public String requestField;
   }

4. Build the project ./mvnw clean install
5. Copy target/trafficparrot-sdk-workspace-x.y.z.jar to directory trafficparrot-enterprise-release-x.y.z/lib/external
6. Look for property trafficparrot.jms.responsetransformers in trafficparrot.properties and add your new class to the list of extension classes there. (Why do I have to edit the extensions properties every time?)
7. Stop Traffic Parrot
8. Start Traffic Parrot
9. Edit an existing JMS mapping and select ChooseResponseQueueBasedOnRequestMessageBody from the "Response transformer" dropdown.
10. Start the JMS virtual service in replay mode and send a JMS request with content {"requestField": "foo"}
11. The response message should be sent to queue response_queue_1
12. Send a JMS request with content {"requestField": "bar"}
13. The response message should be sent to queue response_queue_2