Getting json body in aws Lambda via API gateway

Question

I m currently using NodeJS to build a bot on AWS lambda via AWS Api Gateway and I m running into an issue with POST requests and JSON data  My api uses  Use Lambda Proxy integration  and even when I test the proxy sending a content-type of Application json and some json in the body e g   foo   bar   I can t access the object without parsing it first  e g    var json   JSON parse event body     console log json foo     Now I know this doesn t seem a big deal just running it through JSON parse  but I ve seen a number of other examples where this isn t the case at all  see here https   github com pinzler fb-messenger-bot-aws-lambda blob master index js  Do I need to add anything to my API gateway to handle this correctly  my  request body  step in the  post method request  section has a content-type of application json set-up for the request body    The readme for the example above doesn t seem to use proxy integration as far as I can tell so I m not sure what I should be doing here

User · Answer

I am using lambda with Zappa  I am sending data with POST in json format   My code for basic lambda pure py is   import time import requests import json def my handler event  context       print  Received event      json dumps event  indent 2       print  Log stream name    context log stream name      print  Log group name     context log group name      print  Request ID    context aws request id      print  Mem  limits MB     context memory limit in mb        Code will execute quickly  so we add a 1 second intentional delay so you can see that in time remaining value      print  Time remaining  MS     context get remaining time in millis         if event  httpMethod       GET           hub mode   event  queryStringParameters    hub mode           hub challenge   event  queryStringParameters    hub challenge           hub verify token   event  queryStringParameters    hub verify token           return   statusCode    200    body   hub challenge   headers    Content-Type    application json         if event  httpMethod       post           token    xxxx      params              access token   token           headers              Content-Type    application json                 data     recipient     id   1459299024159359            data update   message     text    text             data   json dumps  data          r   requests post  https   graph facebook com v2 9 me messages  params params  headers headers  data data  timeout 2          return   statusCode    200    body    ok    headers     Content-Type    application json      I got the next json response      resource         path         httpMethod    POST    headers      Accept           Accept-Encoding    deflate  gzip    CloudFront-Forwarded-Proto    https    CloudFront-Is-Desktop-Viewer    true    CloudFront-Is-Mobile-Viewer    false    CloudFront-Is-SmartTV-Viewer    false    CloudFront-Is-Tablet-Viewer    false    CloudFront-Viewer-Country    US    Content-Type    application json    Host    ox53v9d8ug execute-api us-east-1 amazonaws com    Via    1 1 f1836a6a7245cc3f6e190d259a0d9273 cloudfront net  CloudFront     X-Amz-Cf-Id    LVcBZU-YqklHty7Ii3NRFOqVXJJEr7xXQdxAtFP46tMewFpJsQlD2Q      X-Amzn-Trace-Id    Root 1-59ec25c6-1018575e4483a16666d6f5c5    X-Forwarded-For    69 171 225 87  52 46 17 84    X-Forwarded-Port    443    X-Forwarded-Proto    https    X-Hub-Signature    sha1 10504e2878e56ea6776dfbeae807de263772e9f2      queryStringParameters   null   pathParameters   null   stageVariables   null   requestContext      path     dev    accountId    001513791584    resourceId    i6d2tyihx7    stage    dev    requestId    d58c5804-b6e5-11e7-8761-a9efcf8a8121    identity      cognitoIdentityPoolId   null   accountId   null   cognitoIdentityId   null   caller   null   apiKey        sourceIp    69 171 225 87    accessKey   null   cognitoAuthenticationType   null   cognitoAuthenticationProvider   null   userArn   null   userAgent   null   user   null     resourcePath         httpMethod    POST    apiId    ox53v9d8ug      body    eyJvYmplY3QiOiJwYWdlIiwiZW50cnkiOlt7ImlkIjoiMTA3OTk2NDk2NTUxMDM1IiwidGltZSI6MTUwODY0ODM5MDE5NCwibWVzc2FnaW5nIjpbeyJzZW5kZXIiOnsiaWQiOiIxNDAzMDY4MDI5ODExODY1In0sInJlY2lwaWVudCI6eyJpZCI6IjEwNzk5NjQ5NjU1MTAzNSJ9LCJ0aW1lc3RhbXAiOjE1MDg2NDgzODk1NTUsIm1lc3NhZ2UiOnsibWlkIjoibWlkLiRjQUFBNHo5RmFDckJsYzdqVHMxZlFuT1daNXFaQyIsInNlcSI6MTY0MDAsInRleHQiOiJob2xhIn19XX1dfQ      isBase64Encoded   true     my data was on body key  but is code64 encoded  How can I know this  I saw the key isBase64Encoded  I copy the value for body key and decode with This tool and  eureka   I get the values   I hope this help you

User · Answer

You may have forgotten to define the Content-Type header  For example    return       statusCode  200      headers           Content-Type    application json              body  JSON stringify   items

User · Answer

I think there are a few things to understand when working with API Gateway integration with Lambda  Lambda Integration vs Lambda Proxy Integration There used to be only Lambda Integration which requires mapping templates  I suppose this is why still seeing many examples using it   How to pass a querystring or route parameter to AWS Lambda from Amazon API Gateway   As of September 2017  you no longer have to configure mappings to access the request body    Serverless Architecture on AWS   Lambda Proxy Integration  If you enable it  API Gateway will map every request to JSON and pass it to Lambda as the event object  In the Lambda function you   ll be able to retrieve query string parameters  headers  stage variables  path parameters  request context  and the body from it   Without enabling Lambda Proxy Integration  you   ll have to create a mapping template in the Integration Request section of API Gateway and decide how to map the HTTP request to JSON yourself  And you   d likely have to create an Integration Response mapping if you were to pass information back to the client    Before Lambda Proxy Integration was added  users were forced to map requests and responses manually  which was a source of consternation  especially with more complex mappings   Words need to navigate the thinking  To get the terminologies straight   Lambda Proxy Integration   Pass through Simply pass the HTTP request through to lambda   Lambda Integration   Template transformation Go through a transformation process using the Apache Velocity template and you need to write the template by yourself    body is escaped string  not JSON Using Lambda Proxy Integration  the body in the event of lambda is a string escaped with backslash  not a JSON   quot body quot    quot    quot foo  quot    quot bar  quot   quot    If tested in a JSON formatter  Parse error on line 1     quot foo  quot    quot bar  quot   -  Expecting  STRING        got  undefined   The document below is about response but it should apply to request   I received a  quot malformed Lambda proxy response quot  error or a 502 status code with Amazon API Gateway  How do I resolve this    The body field  if you are returning JSON  must be converted to a string or it will cause further problems with the response  You can use JSON stringify to handle this in Node js functions  other runtimes will require different solutions  but the concept is the same   For JavaScript to access it as a JSON object  need to convert it back into JSON object with json parse in JapaScript  json dumps in Python   How To Work with JSON in JavaScript   Strings are useful for transporting but you   ll want to be able to convert them back to a JSON object on the client and or the server side   The AWS documentation shows what to do  if  event body     null  amp  amp  event body     undefined        let body   JSON parse event body      if  body time           time   body time        var response         statusCode  responseCode      headers             quot x-custom-header quot     quot my custom header value quot             body  JSON stringify responseBody     console log  quot response   quot    JSON stringify response   callback null  response

User · Answer

There are two different Lambda integrations you can configure in API Gateway  such as Lambda integration and Lambda proxy integration  For Lambda integration  you can customise what you are going to pass to Lambda in the payload that you don t need to parse the body  but when you are using Lambda Proxy integration in API Gateway  API Gateway will proxy everything to Lambda in payload like this          message    Hello me         input              path     test hello            headers                  Accept    text html application xhtml xml application xml q 0 9 image webp     q 0 8                Accept-Encoding    gzip  deflate  lzma  sdch  br                Accept-Language    en-US en q 0 8                CloudFront-Forwarded-Proto    https                CloudFront-Is-Desktop-Viewer    true                CloudFront-Is-Mobile-Viewer    false                CloudFront-Is-SmartTV-Viewer    false                CloudFront-Is-Tablet-Viewer    false                CloudFront-Viewer-Country    US                Host    wt6mne2s9k execute-api us-west-2 amazonaws com                Upgrade-Insecure-Requests    1                User-Agent    Mozilla 5 0  Macintosh  Intel Mac OS X 10 11 6  AppleWebKit 537 36  KHTML  like Gecko  Chrome 52 0 2743 82 Safari 537 36 OPR 39 0 2256 48                Via    1 1 fb7cca60f0ecd82ce07790c9c5eef16c cloudfront net  CloudFront                 X-Amz-Cf-Id    nBsWBOrSHMgnaROZJK1wGCZ9PcRcSpq oSXZNQwQ10OTZL4cimZo3g                  X-Forwarded-For    192 168 100 1  192 168 1 1                X-Forwarded-Port    443                X-Forwarded-Proto    https                      pathParameters     proxy    hello             requestContext                  accountId    123456789012                resourceId    us4z18                stage    test                requestId    41b45ea3-70b5-11e6-b7bd-69b5aaebc7d9                identity                      cognitoIdentityPoolId                        accountId                        cognitoIdentityId                        caller                        apiKey                        sourceIp    192 168 100 1                    cognitoAuthenticationType                        cognitoAuthenticationProvider                        userArn                        userAgent    Mozilla 5 0  Macintosh  Intel Mac OS X 10 11 6  AppleWebKit 537 36  KHTML  like Gecko  Chrome 52 0 2743 82 Safari 537 36 OPR 39 0 2256 48                    user                                  resourcePath      proxy                  httpMethod    GET                apiId    wt6mne2s9k                      resource      proxy              httpMethod    GET            queryStringParameters     name    me             stageVariables     stageVarName    stageVarValue             body       foo     bar               isBase64Encoded   false           For the example you are referencing  it is not getting the body from the original request  It is constructing the response body back to API Gateway  It should be in this format          statusCode   httpStatusCode       headers      headerName    headerValue               body               isBase64Encoded   false

[aws-lambda] Getting json body in aws Lambda via API gateway

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