AWS API Gateway : Convert response to XML - amazon-web-services

Question

I am getting a string value (xml to string) from lambda backend which should be returned to end user in application/xml format. How can I achieve this?

Answer 1

You can specify an Integration Response that returns XML, along with a mapping template to format XML using the object returned from Lambda.
I do not believe there is a default format conversion to XML. A simple mapping template might be like this:
#set($root = $input.path('$'))
<stuff>
<message>$root.message</message>
<sourceIp>$context.identity.sourceIp</sourceIp>
<outputs>
#foreach($key in $root.keySet())
<output>
<key>$key</key>
<value>$root.get($key)</value>
</output>
#end
</outputs>
</stuff>

Answer 2

With reference to this document, section "Accessing the $util Variable", solved the challenge in a simple JSON to XML transform. I did try the mapping template given earlier here, but it did not work for me.
In my case, my JSON response payload is of the form:
[
{
"key1": "val1",
"key2": "val2",
"key3": "val3"
},
{
"key1": "val1",
"key2": "val2",
"key3": "val3",
"key4": "val4"
}
]
Here is the mapping template that deals with it:
#set ($arr = $util.parseJson($input.path('$')))
<responses>
#foreach($c in $arr)
<response>
#foreach ($k in $c.keySet())
<$k>$c.get($k)</$k>#end
</response>
#end
</responses>
The key was the parseJson to get a true JSON/Java object. After thi it was smooth sailing.
And the output is of the form:
<responses>
<response>
<key1>val1</key1>
...
</response>
...
</responses>
I hope this helps.