How do I query this auto generated AWS Amplify API? - node.js

Question

I am trying to query an autogenerated Amplify API using postman. I'm banging my head against the wall on something that should be simple. Can someone explain why this query URL doesn't return a JSON object?. The data exists in dynamo but returns an empty array in postman (and a 200 status):
POSTMAN (this is what I expected to work):
https://xxxxx.execute-api.us-east-1.amazonaws.com/staging/api/getShipContainer?location=fl
UPDATE after staring at the code for longer I see that req.params[partitionKeyName] is somehow evaluating to getShipContainer which would explain my issue, but how do I fix this? And why did it happen:
condition[partitionKeyName]['AttributeValueList'] = [ convertUrlType(req.params[partitionKeyName], partitionKeyType) ];
This syntax works (returns dynamo object) but is very clearly incorrect (location is a dynamo column, and fl is the filter param): https://xxxxxx.execute-api.us-east-1.amazonaws.com/staging/api/fl?location
Query method:
const userIdPresent = false; // TODO: update in case is required to use that definition
const partitionKeyName = "location";
const partitionKeyType = "S";
const sortKeyName = "containerId";
const sortKeyType = "S";
const hasSortKey = sortKeyName !== "";
const path = "/api";
const UNAUTH = 'UNAUTH';
const hashKeyPath = '/:' + partitionKeyName;
const sortKeyPath = hasSortKey ? '/:' + sortKeyName : '';
// declare a new express app
var app = express()
app.use(bodyParser.json())
app.use(awsServerlessExpressMiddleware.eventContext())
//Enable CORS for all methods
app.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "*")
res.header("Access-Control-Allow-Headers", "*")
next()
});
// convert url string param to expected Type
const convertUrlType = (param, type) => {
switch(type) {
case "N":
return Number.parseInt(param);
default:
return param;
}
}
/********************************
* HTTP Get method for list objects *
********************************/
//api/:location
app.get(path + hashKeyPath, function(req, res) {
var condition = {}
condition[partitionKeyName] = {
ComparisonOperator: 'EQ'
}
if (userIdPresent && req.apiGateway) {
condition[partitionKeyName]['AttributeValueList'] = [req.apiGateway.event.requestContext.identity.cognitoIdentityId || UNAUTH ];
} else {
try {
condition[partitionKeyName]['AttributeValueList'] = [ convertUrlType(req.params[partitionKeyName], partitionKeyType) ];
} catch(err) {
res.statusCode = 500;
res.json({error: 'Wrong column type ' + err});
}
}
let queryParams = {
TableName: tableName,
KeyConditions: condition
}
console.log(`req gg cond::`,JSON.stringify(condition),`params`,Object.entries(req.params).map(([i,k])=>i+' '+k).join(','))
dynamodb.query(queryParams, (err, data) => {
if (err) {
res.statusCode = 500;
res.json({error: 'Could not load items: ' + err});
} else {
res.json(data.Items);
}
});
});
results of the console.log I put in to debug:
req gg cond::
{
"location": {
"ComparisonOperator": "EQ",
"AttributeValueList": [
"getShipContainer"
]
}
}
params location getShipContainer
shouldn't the expected query be using LOCATION and ignoring "getShipContainer" completely? Im very confused because the code was auto generated. getShipContainer is the name of the lambda function that is being called
I also tested this in the API Gateway test console with the same result:
Here is a quick screenshot of my dynamo table as well:

Answer 1

the issue is mentioned in this github issue.
change your handler function to this, and https://xxxxx.execute-api.us-east-1.amazonaws.com/staging/api/location will return the list of items.
app.get(path + hashKeyPath, function (req, res) {
let scanParams = {
TableName: tableName,
};
dynamodb.scan(scanParams, (err, data) => {
if (err) {
res.statusCode = 500;
res.json({ error: "Could not load items: " + err });
} else {
res.json(data.Items);
}
});
});
And here's the code for filtering if the parameter is specified in the URL.
Location is one of the dynamodb reserved word, so I've used attribute mapping.
https://xxxxx.execute-api.us-east-1.amazonaws.com/staging/api/location?location=fl
app.get(path + hashKeyPath, function (req, res) {
var filterParams = {};
const location = req.query[partitionKeyName] || "";
if (location) {
filterParams = {
FilterExpression: "#loc = :loc",
ExpressionAttributeNames: {
"#loc": "location",
},
ExpressionAttributeValues: {
":loc": location,
},
};
}
let scanParams = {
TableName: tableName,
...filterParams,
};
dynamodb.scan(scanParams, (err, data) => {
if (err) {
res.statusCode = 500;
res.json({ error: "Could not load items: " + err });
} else {
res.json(data.Items);
}
});
});
Usually I use DynamoDB Global Secondary Index to query all items. But it might be depends on the use case. For example, I've used to query List of Items by its Site Id.
Table would be something like this:
itemID
itemName
siteID
router.get("/", function (req, res) {
const sortKeyName = "siteID";
let queryParams = {
TableName: tableName,
IndexName: "siteIDGSI",
KeyConditionExpression: "siteID = :site_id",
ExpressionAttributeValues: {
":site_id": req.params[sortKeyName],
},
};
dynamodb.query(queryParams, (err, data) => {
if (err) {
res.statusCode = 500;
res.json({ error: "Could not load items: " + err });
} else {
res.json({
statusCode: 200,
message: "List of Items in " + req.params[sortKeyName],
items: data.Items,
});
}
});
});
So you can create GSI for containerId