Use Topic object when communicating with amazon SNS api through mule - amazon-web-services

Question

I'm using Anypoint Studio to experiment with connectors. At this point, i'm trying to make a simple flow that lists topics available at the amazon SNS endpoint and searches if a certain topic is available.
So far, i'm able to get a response from the API with the list of topics, which i then transform to json using Object to JSON transformer, but i want to iterate through the list to search for a certain topic(using java or whatever filter). The topic entity already exists in the amazon API in Anypoint Studio but i can't find out how to map it to the response returned by the API. Any hint would be appreciated.
EDIT: Here is the code of the flow, removed access keys.
<?xml version="1.0" encoding="UTF-8"?>
<sns:config name="Amazon_SNS" accessKey="" secretKey="" doc:name="Amazon SNS" region="EUWEST1">
<sns:connection-pooling-profile initialisationPolicy="INITIALISE_ONE" exhaustedAction="WHEN_EXHAUSTED_GROW"/>
</sns:config>
<http:listener-config name="HTTP_Listener_Configuration" host="localhost" port="8081" doc:name="HTTP Listener Configuration"/>
<json:object-to-json-transformer name="Object_to_JSON" doc:name="Object to JSON"/>
<flow name="CreateTopic">
<http:listener config-ref="HTTP_Listener_Configuration" path="/createtopic" doc:name="HTTP"/>
<sns:create-topic config-ref="Amazon_SNS" doc:name="Amazon SNS">
<sns:create-topic-request name="#[message.inboundProperties.'http.query.params'.name]"/>
</sns:create-topic>
<json:object-to-json-transformer doc:name="Object to JSON"/>
</flow>
<flow name="Subscribe">
<http:listener config-ref="HTTP_Listener_Configuration" path="/Subscribe" doc:name="HTTP"/>
<sns:subscribe config-ref="Amazon_SNS" doc:name="Amazon SNS">
<sns:subscribe-request topicArn="#[message.inboundProperties.'http.query.params'.topic]" protocol="email" endpoint="#[message.inboundProperties.'http.query.params'.subscriber]"/>
</sns:subscribe>
<json:object-to-json-transformer doc:name="Object to JSON"/>
</flow>
<flow name="ListTopics">
<http:listener config-ref="HTTP_Listener_Configuration" path="/listTopics" doc:name="HTTP"/>
<sns:list-topics config-ref="Amazon_SNS" doc:name="Amazon SNS">
</sns:list-topics>
<json:object-to-json-transformer doc:name="Object to JSON"/>
</flow>
<flow name="Publish">
<http:listener config-ref="HTTP_Listener_Configuration" path="/publish" doc:name="HTTP"/>
<sns:publish config-ref="Amazon_SNS" doc:name="Amazon SNS">
<sns:publish-request topicArn="#[message.inboundProperties.'http.query.params'.topic]" message="There's new content in the topic #[message.inboundProperties.'http.query.params'.topic]" subject="New comments on an idea - Crowdsourcing Forums" messageStructure="Raw"/>
</sns:publish>
<json:object-to-json-transformer doc:name="Object to JSON"/>
</flow>
<flow name="checkTopic">
<http:listener config-ref="HTTP_Listener_Configuration" path="/checkTopic" doc:name="HTTP"/>
<sns:get-topic-attributes config-ref="Amazon_SNS" doc:name="Amazon SNS">
<sns:get-topic-attributes-request topicArn="#[message.inboundProperties.'http.query.params'.topic]"/>
</sns:get-topic-attributes>
</flow>

Answer 1

The message payload you get from sns:list-topics is a com.amazonaws.services.sns.model.ListTopicsResult.
So you can use a MEL transformer to filter the topic list with an expression like:
($ in message.payload.topics if $.topicArn contains 'my-topic')
Reference: Projections and folds in MVEL 2.0