How to pass a querystring or route parameter to AWS Lambda from Amazon API Gateway

Question

for instance if we want to use   GET  user name bob  or  GET  user bob  How would you pass both of these examples as a parameter to the Lambda function   I saw something about setting a  mapped from  in the documentation  but I can t find that setting in the API Gateway console    method request path parameter-name for a path parameter named parameter-name as defined in the Method Request page  method request querystring parameter-name for a query string parameter named parameter-name as defined in the Method Request page    I don t see either of these options even though I defined a query string

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After reading several of these answers  I used a combination of several in Aug of 2018 to retrieve the query string params through lambda for python 3 6    First  I went to API Gateway -  My API -  resources  on the left  -  Integration Request  Down at the bottom  select Mapping Templates then for content type enter application json    Next  select the Method Request Passthrough template that Amazon provides and select save and deploy your API    Then in  lambda event  params   is how you access all of your parameters  For query string  event  params    querystring

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As part of trying to answer one of my own questions here  I came across this trick   In the API Gateway mapping template  use the following to give you the complete query string as sent by the HTTP client          querystring     input params   querystring      The advantage is that you don t have to limit yourself to a set of predefined mapped keys in your query string  Now you can accept any key-value pairs in the query string  if this is how you want to handle    Note   According to this  only  input params x  is listed as a variable made available for the VTL template  It is possible that the internals might change and querystring may no longer be available

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Refer Doc   https   docs aws amazon com apigateway latest developerguide integrating-api-with-aws-services-lambda html api-as-lambda-proxy-expose-get-method-with-path-parameters-to-call-lambda-function  You need to modify the Mapping Template

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Now you should be able to use the new proxy integration type for Lambda to automatically get the full request in standard shape  rather than configure mappings   see  http   docs aws amazon com apigateway latest developerguide api-gateway-set-up-simple-proxy html api-gateway-set-up-lambda-proxy-integration-on-proxy-resource

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My goal was to pass a query string similar to   protodb sql select   from protodb prototab  to a Node js 12 Lambda function via a URL from the API gateway  I tried a number of the ideas from the other answers but really wanted to do something in the most API gateway UI native way possible  so I came up with this that worked for me  as of the UI for API Gateway as of December 2020   On the API Gateway console for a given API  under resources  select the get method  Then select its Integration Request and fill out the data for the lambda function at the top of the page  Scroll to the bottom and open up the mapping templates section  Choose Request Body Passthrough when there are no templates defined  recommended   Click on Add mapping templates and create one with the content-type of application json and hit the check mark button  For that mapping template  choose the Method Request passthrough on the drop down list for generate template which will fill the textbox under it with AWS  general way to pass everything  Hit the save button  Now when I tested it  I could not get the parameter to come through as event sql under node JS in the Lambda function  It turns out that when the API gateway sends the URL sql query parameter to the Lambda function  it comes through for Node js as   var insql   event params querystring sql   So the trick that took some time for me was to use JSON stringify to show the full event stack and then work my way down through the sections to be able to pull out the sql parameter from the query string  So basically you can use the default passthrough functionality in the API gateway with the trick being how the parameters are passed when you are in the Lambda function

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The following parameter-mapping example passes all parameters  including path  querystring and header  through to the integration endpoint via a JSON payload   set  allParams    input params         params           foreach  type in  allParams keySet         set  params    allParams get  type         type             foreach  paramName in  params keySet            paramName      util escapeJavaScript  params get  paramName           if  foreach hasNext   end        end            if  foreach hasNext   end      end         In effect  this mapping template outputs all the request parameters in the payload as outlined as follows        parameters            path                  path name     path value                            header                header name     header value                           querystring              querystring name     querystring value                              Copied from the Amazon API Gateway Developer Guide

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The Lambda function expects JSON input  therefore parsing the query string is needed  The solution is to change the query string to JSON using the Mapping Template I used it for C   NET Core  so the expected input should be a JSON with  queryStringParameters  parameter  Follow these 4 steps below to achieve that    Open the mapping template of your API Gateway resource and add new application json content-tyap       Copy the template below  which parses the query string into JSON  and paste it into the mapping template      queryStringParameters     foreach  key in  input params   querystring keySet    if  foreach index  gt  0   end  key    input params   querystring get  key   end     In the API Gateway  call your Lambda function and add the following query string  for the example   param1 111 amp param2 222 amp param3 333 The mapping template should create the JSON output below  which is the input for your Lambda function       queryStringParameters     param3   333   param1   111   param2   222      You re done  From this point  your Lambda function s logic can use the query string parameters  Good luck

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exports handler   async  event    gt        let query   event queryStringParameters      console log  id    query id         const response             statusCode  200          body   quot Hi quot              return response

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The query string is straight forward to parse in javascript in the lambda   for GET  user name bob   var name   event params querystring name    This doesn t solve the GET user bob question though

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Python 3 8 with boto3 v1 16v - 2020 December For configuring routes  you have to configure API Gateway to accept routes  otherwise other than the base route everything else will end up in a  missing auth token  or something other    Once you configured API Gateway to accept routes  make sure that you enabled lambda proxy  so that things will work better  to access routes  new route   event  path       some url   to access query parameter query param   event  queryStringParameters    query key

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GET  user name bob         name     input params   querystring get  name        GET  user bob         name     input params  name

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The accepted answer worked fine for me  but expanding on gimenete s answer  I wanted a generic template I could use to pass through all query path header params  just as strings for now   and I came up the following template  I m posting it here in case someone finds it useful    set  keys        foreach  key in  input params   querystring keySet       set  success    keys add  key    end   foreach  key in  input params   headers keySet       if   keys contains  key        set  success    keys add  key      end  end   foreach  key in  input params   path keySet       if   keys contains  key        set  success    keys add  key      end  end     foreach  key in  keys      key     util escapeJavaScript  input params  key    if  foreach hasNext   end  end

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These days a drop-down template is included in the API Gateway Console on AWS   For your API  click on the resource name    then GET  Expand  Body Mapping Templates   Type in      application json   for Content-Type  must be explicitly typed out  and click the tick  A new window will open with the words  Generate template  and a dropdown  see image    Select      Method Request passthrough     Then click save  To access any variables  just use the following syntax  this is Python  e g  URL   https   yourURL execute-api us-west-2 amazonaws com prod confirmReg token 12345 amp uid 5   You can get variables as follows   from   future   import print function  import boto3 import json  print  Loading function     def lambda handler event  context       print event  params    querystring    token        print event  params    querystring    uid      So there is no need to explicitly name or map each variable you desire

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As  Jonathan s answer  after mark Use Lambda Proxy integration in Integration Request  in your source code you should implement as below format to by pass 502 Bad Gateway error   NodeJS 8 10   exports handler   async  event  context  callback    gt         TODO  You could get path  parameter  headers  body value from this   const   path  queryStringParameters  headers  body     event     const response          statusCode   200       headers            Content-Type    application json              body   JSON stringify         path         query  queryStringParameters        headers        body  JSON parse body               isBase64Encoded   false         return response       Don t forget deploy your resource at API Gateway before re-run your API  Response JSON just return which set in body is correct  So  you could get path  parameter  headers  body value from event     const   path  queryStringParameters  headers  body     event

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A lot of the answers here are great  But I wanted something a little simpler  I wanted something that will work with the  Hello World  sample for free  This means I wanted a simple produces a request body that matches the query string      foreach  param in  input params   querystring keySet        param     util escapeJavaScript  input params   querystring get  param     if  foreach hasNext   end  end     I think the top answer produces something more useful when building something real  but for getting a quick hello world running using the template from AWS this works great

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You can used Lambda as  Lambda Proxy Integration   ref this  https   docs aws amazon com apigateway latest developerguide api-gateway-create-api-as-simple-proxy-for-lambda html api-gateway-proxy-integration-lambda-function-python    options avalible to this lambda are   For Nodejs Lambda  event headers    event pathParameters    event body    event stageVariables    and  event requestContext   For Python Lambda event  headers    parametername   and so on

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In order to pass parameters to your lambda function you need to create a mapping between the API Gateway request and your lambda function  The mapping is done in the Integration Request -  Mapping templates section of the selected API Gateway resource   Create a mapping of type application json  then on the right you will edit  click the pencil  the template   A mapping template is actually a Velocity template where you can use ifs  loops and of course print variables on it  The template has these variables injected where you can access querystring parameters  request headers  etc  individually  With the following code you can re-create the whole querystring          querystring      foreach  key in  input params   querystring keySet    if  foreach index  gt  0  amp  end util urlEncode  key   util urlEncode  input params   querystring get  key   end        body     input json          Note  click on the check symbol to save the template  You can test your changes with the  test  button in your resource  But in order to test querystring parameters in the AWS console you will need to define the parameter names in the Method Request section of your resource   Note  check the Velocity User Guide for more information about the Velocity templating language   Then in your lambda template you can do the following to get the querystring parsed   var query   require  querystring   parse event querystring     access parameters with query  foo   or query foo

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I have used this mapping template to provide Body  Headers  Method  Path  and URL Query String Parameters to the Lambda event   I wrote a blog post explaining the template in more detail   http   kennbrodhagen net 2015 12 06 how-to-create-a-request-object-for-your-lambda-event-from-api-gateway   Here is the Mapping Template you can use        method     context httpMethod      body     input json          headers          foreach  param in  input params   header keySet          param     util escapeJavaScript  input params   header get  param     if  foreach hasNext   end       end         queryParams          foreach  param in  input params   querystring keySet          param     util escapeJavaScript  input params   querystring get  param     if  foreach hasNext   end       end         pathParams          foreach  param in  input params   path keySet          param     util escapeJavaScript  input params   path get  param     if  foreach hasNext   end       end

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As of September 2017  you no longer have to configure mappings to access the request body   All you need to do is check   Use Lambda Proxy integration   under Integration Request  under the resource     You ll then be able to access query parameters  path parameters and headers like so  event  pathParameters    param1   event  queryStringParameters    queryparam1   event  requestContext    identity    userAgent   event  requestContext    identity    sourceIP

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The steps to get this working are   Within the API Gateway Console       go to Resources - gt  Integration Request click on the plus or edit icon next to templates dropdown  odd I know since the template field is already open and the button here looks greyed out  Explicitly type application json in the content-type field even though it shows a default  if you don t do this it will not save and will not give you an error message  put this in the input mapping    name     input params  name      click on the check box next to the templates dropdown  I m assuming this is what finally saves it

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The way that works for me is to  Go to Integration Request click URL Query String Parameters click Add query string in name field put the query name  which is  quot name quot  here in Mapped From field  put  quot method request querystring name quot

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