Lambda and API gateway mapping - aws-lambda

Question

I want to return a value from handler to API gateway response header.
Handler.js
module.exports.handler = function(event, context, cb) {
const UpdateDate = new Date();
return cb(null, {
body: {
message: 'test'
},
header: {
Last-Modified: UpdateDate
}
});
};
s-function.json in "endpoints"
"responses": {
"400": {
"statusCode": "400"
},
"default": {
"statusCode": "200",
"responseParameters": {
"method.response.header.Cache-Control": "'public, max-age=86400'",
"method.response.header.Last-Modified": "integration.response.body.header.Last-Modified"
},
"responseModels": {
"application/json;charset=UTF-8": "Empty"
},
"responseTemplates": {
"application/json;charset=UTF-8": "$input.json('$.body')"
}
}
}
This can work. But I want to know how to use "integration.response.header.Last-Modified". Is my handler callback formate wrong?
Edit:
s-function.json in "endpoints"
"integration.response.header.Last-Modified" This doesn't work.
I want to know specific handler return formate to pass data to "integration.response.header.Last-Modified".
"responses": {
"400": {
"statusCode": "400"
},
"default": {
"statusCode": "200",
"responseParameters": {
"method.response.header.Cache-Control": "'public, max-age=86400'",
"method.response.header.Last-Modified": "integration.response.header.Last-Modified"
},
"responseModels": {
"application/json;charset=UTF-8": "Empty"
},
"responseTemplates": {
"application/json;charset=UTF-8": "$input.json('$.body')"
}
}
}

Answer 1

All of the output from your lambda function is returned in the response body, so you will need to map part of the response body to your API response header.
module.exports.handler = function(event, context, cb) {
const UpdateDate = new Date();
return cb(null, {
message: 'test',
Last-Modified: UpdateDate
});
};
will produce payload "{"message" : "test", "Last-Modified" : "..."}"
In this case you would use "integration.response.body.Last-Modified" as the mapping expression. As a side note, naming things "body" and "header" in your response body may make the mapping expressions confusing to read.
Thanks,
Ryan