# Call the API using a REST API client
<a name="api-as-s3-proxy-test-using-postman"></a>

To provide an end-to-end tutorial, we now show how to call the API using [Postman](https://www.postman.com/), which supports the AWS IAM authorization.<a name="api-as-s3-proxy-test-using-postman-steps"></a>

**To call our Amazon S3 proxy API using Postman**

1. Deploy or redeploy the API. Make a note of the base URL of the API that is displayed next to **Invoke URL** at the top of the **Stage Editor**.

1. Launch Postman.

1. Choose **Authorization** and then choose `AWS Signature`. Enter your IAM user's Access Key ID and Secret Access Key into the **AccessKey** and **SecretKey**input fields, respectively. Enter the AWS Region to which your API is deployed in the **AWS Region** text box. Enter `execute-api` in the **Service Name** input field.

   You can create a pair of the keys from the **Security Credentials** tab from your IAM user account in the IAM Management Console.

1. To add a bucket named `amzn-s3-demo-bucket` to your Amazon S3 account in the `{region}` region:

   1. Choose **PUT** from the drop-down method list and type the method URL (`https://api-id.execute-api.aws-region.amazonaws.com/stage/folder-name`

   1. Set the `Content-Type` header value as `application/xml`. You may need to delete any existing headers before setting the content type.

   1. Choose **Body** menu item and type the following XML fragment as the request body:

      ```
      <CreateBucketConfiguration> 
        <LocationConstraint>{region}</LocationConstraint> 
      </CreateBucketConfiguration>
      ```

   1. Choose **Send** to submit the request. If successful, you should receive a `200 OK` response with an empty payload. 

1. To add a text file to a bucket, follow the instructions above. If you specify a bucket name of **amzn-s3-demo-bucket** for `{folder}` and a file name of **Readme.txt** for `{item}` in the URL and provide a text string of **Hello, World\$1** as the file contents (thereby making it the request payload), the request becomes

   ```
   PUT /S3/amzn-s3-demo-bucket/Readme.txt HTTP/1.1
   Host: 9gn28ca086.execute-api.{region}.amazonaws.com
   Content-Type: application/xml
   X-Amz-Date: 20161015T062647Z
   Authorization: AWS4-HMAC-SHA256 Credential=access-key-id/20161015/{region}/execute-api/aws4_request, SignedHeaders=content-length;content-type;host;x-amz-date, Signature=ccadb877bdb0d395ca38cc47e18a0d76bb5eaf17007d11e40bf6fb63d28c705b
   Cache-Control: no-cache
   Postman-Token: 6135d315-9cc4-8af8-1757-90871d00847e
   
   Hello, World!
   ```

   If everything goes well, you should receive a `200 OK` response with an empty payload.

1. To get the content of the `Readme.txt` file we just added to the `amzn-s3-demo-bucket` bucket, do a GET request like the following one:

   ```
   GET /S3/amzn-s3-demo-bucket/Readme.txt HTTP/1.1
   Host: 9gn28ca086.execute-api.{region}.amazonaws.com
   Content-Type: application/xml
   X-Amz-Date: 20161015T063759Z
   Authorization: AWS4-HMAC-SHA256 Credential=access-key-id/20161015/{region}/execute-api/aws4_request, SignedHeaders=content-type;host;x-amz-date, Signature=ba09b72b585acf0e578e6ad02555c00e24b420b59025bc7bb8d3f7aed1471339
   Cache-Control: no-cache
   Postman-Token: d60fcb59-d335-52f7-0025-5bd96928098a
   ```

   If successful, you should receive a `200 OK` response with the `Hello, World!` text string as the payload.

1. To list items in the `amzn-s3-demo-bucket` bucket, submit the following request:

   ```
   GET /S3/amzn-s3-demo-bucket HTTP/1.1
   Host: 9gn28ca086.execute-api.{region}.amazonaws.com
   Content-Type: application/xml
   X-Amz-Date: 20161015T064324Z
   Authorization: AWS4-HMAC-SHA256 Credential=access-key-id/20161015/{region}/execute-api/aws4_request, SignedHeaders=content-type;host;x-amz-date, Signature=4ac9bd4574a14e01568134fd16814534d9951649d3a22b3b0db9f1f5cd4dd0ac
   Cache-Control: no-cache
   Postman-Token: 9c43020a-966f-61e1-81af-4c49ad8d1392
   ```

   If successful, you should receive a `200 OK` response with an XML payload showing a single item in the specified bucket, unless you added more files to the bucket before submitting this request.

   ```
   <?xml version="1.0" encoding="UTF-8"?>
   <ListBucketResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
       <Name>apig-demo-5</Name>
       <Prefix></Prefix>
       <Marker></Marker>
       <MaxKeys>1000</MaxKeys>
       <IsTruncated>false</IsTruncated>
       <Contents>
           <Key>Readme.txt</Key>
           <LastModified>2016-10-15T06:26:48.000Z</LastModified>
           <ETag>"65a8e27d8879283831b664bd8b7f0ad4"</ETag>
           <Size>13</Size>
           <Owner>
               <ID>06e4b09e9d...603addd12ee</ID>
               <DisplayName>user-name</DisplayName>
           </Owner>
           <StorageClass>STANDARD</StorageClass>
       </Contents>
   </ListBucketResult>
   ```

**Note**  
To upload or download an image, you need to set content handling to CONVERT\$1TO\$1BINARY.