GET requests fail when passing through the ArcGIS Web Adaptor

Description

When attempting to perform GET requests through the ArcGIS Web Adaptor, the request fails with the following error: 

Error:
Error 404.15: The request filtering module is configured to deny a request where the query string is too long.

Note:
The error is an error returned by the browser used. The error message returned may vary accordingly to the browser used in the request.

Cause

This problem occurs if the request query is too long and it exceeds the maxQueryLength parameters limit. By default, the maximum amount of characters set in the maxQueryLength parameter is 2000 characters. However, some requests can exceed this amount, since special characters such as quotes ('') and double quotes ("") are converted into URL-encoded values. For example, %27 is a single quote (').

For more information about URL-encoded values, refer to the following W3Schools reference guide, HTML URL Encoding Reference.

Solution or Workaround

The maxQueryStringLength parameter that resides in the httpRuntime tag in the web.config file can be modified to accept a larger number of characters. Use the following instructions to modify the web.config file:

1. Open the web.config file using a text editor (for example, Notepad or Notepad++).
2. Search for maxQueryStringLength and modify the value. The following code snippet shows an example of the final code.

...
<httpRuntime maxRequestLength="2097151" maxQueryStringLength="2097151" maxUrlLength="2097151" executionTimeout="100000" />
...