[ESB] Aggregate Responses with WSO2 Aggregate Mediator

Aggregate mediator can be used to merge several responses and create one response by matching the Xpaths.

In this blog post I'm going to demonstrate how to aggregates the response messages which were split by Iterator Mediator. 

The flowing proxy wrote to get the GitHub Contributors details for a specified repository.

 

The response message of this proxy is as shown below.

But the expected response message is as shown below.

 

Solution :

To get the expected response message  need to merge the sub messages in to one. We can do this using Aggregate Mediator.

To do this  need to add the Aggregate Mediator inside the out sequence as shown in below figure.

 

In the aggregate mediator we need to add the following parameters.

Aggregate Id : you can give any proper Id . This parameter is an optional thing

Aggregation Expression : This is the Xpath expression specifying based on which elements to aggregate.

Completion Max-messages : -1
Completion Min-messages : -1

There are maximum and minimum number of messages that can exists in aggregation . Here I used both cases as -1 because I need to aggregate all the messages.

EnclosingElementProperty : This is used to accumulate the aggregated messages inside single property.

Here I used this as “ROOT”. This property need to define in the proxy as follows.

<property name="ROOT" scope="default">

<root xmlns=""/>

</property>

[ESB]Transform Message Content using Payload Factory Mediator in WSO2 ESB

Payload Factory Mediator 

 

 

This mediator can be used to transform/replace the content of a message in to desired format(XML/JSON/text).

Eg: Let's consider about a client server system.

Server sends the JSON format responses , but in the client side understand the XML format responses only. In this case we need to transform the JSON format responses in to XML format responses. We can do this using Payload Factory Mediator. 

How to transform a message JSON to XML format

Sample response in JSON format .

{

    "login": "peff",

    "id": 45925,

    "avatar_url":
"https://avatars.githubusercontent.com/u/45925?v=3",

    "gravatar_id": "",

    "url":
"https://api.github.com/users/peff",

    "html_url":
"https://github.com/peff",

    "followers_url":
"https://api.github.com/users/peff/followers",

    "following_url":
"https://api.github.com/users/peff/following{/other_user}",

    "gists_url":
"https://api.github.com/users/peff/gists{/gist_id}",

    "starred_url":
"https://api.github.com/users/peff/starred{/owner}{/repo}",

    "subscriptions_url":
"https://api.github.com/users/peff/subscriptions",

    "organizations_url":
"https://api.github.com/users/peff/orgs",

    "repos_url":
"https://api.github.com/users/peff/repos",

    "events_url":
"https://api.github.com/users/peff/events{/privacy}",

    "received_events_url":
"https://api.github.com/users/peff/received_events",

    "type": "User",

    "site_admin": true,

    "contributions": 2065

  }

Let's transform the above response in to following XML format .

<contributor>

<name>peff</name>

<contribution>2065</contribution>

</contributor>

You can do this by adding the following payloadFactory mediator .

<payloadFactory media-type="xml">

<format>

<contributor xmlns="">

<name>$1</name>

<contribution>$2</contribution>

</contributor>

</format>

<args>

<arg expression="//jsonElement/login/text()" evaluator="xml"/>

<arg expression="//jsonElement/contributions/text()" evaluator="xml"/>

</args>

</payloadFactory>

You can create a payloadFactory through the UI.

To do this first you need to add the payloadFactory mediator inside the insequence of the proxy service as shown below.

 

Then you can create the payload format and you can add the arguments using Xpath expressions as shown in below figure.