Content is not allowed in prolog messages in the VSE log files

Products

• CA Application Test
• Service Virtualization
• CA Continuous Application Insight (PathFinder)

Issue/Introduction

We are getting the following error messages in the vse.log files:
ERROR System.err                     - [Fatal Error] :1:1: Content is not allowed in prolog.

Cause

This error message indicates something is invalid with XML content being parsed.

Environment

All supported DevTest releases.

Resolution

This error message is usually preceded by the Virtual Service name causing the issue. 

• Open the Virtual Service Model and verify if the Data Protocol Handlers in the request and response sides are the correct ones.

Example: if JSON requests are being sent to the VSM, the filter/ DPH needs to be JSON.

• Verify the requests being sent to the VSM if they are valid requests.
• Verify the VSI responses, if they are valid responses.