webMethods Knowlegebase : HTTTP Post doesn't work with redirect (HTTP/1.1 307) (1786995)

Problem

When you send a http POST via the service pub.client:http to a load balanced system and the load balancer responds with a redirect (HTTP/1.1 307), then the POST isn't sent to the redirected system, instead a GET without payload is sent to the redirected system.

From HTTP-Trace:

POST to <host>:8102:

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> POST /sap/bc/idoc_xml?sap-client=222 HTTP/1.1

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> User-Agent: Mozilla/4.0 [en] (WinNT; I)

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Accept: image/gif, */*

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Host: <host>:8102

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Authorization:IMERCATOCPIC: ****

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Content-Type: text/xml; charset=utf-8

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Content-Length: 46381

2017-10-23 16:39:54 CEST [ISC.0040.0001D] HTTP/1.1 307

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- Content-Type: text/html; charset=utf-8

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- Content-Length: 277

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- location: http://<host>:8002/sap/bc/idoc_xml?sap-client=222

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- host: <host>:8102

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- date: Mon, 23 Oct 2017 14:39:54 GMT

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- server: SAP Message Server, release 742 (ET1)

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- connection: close

Redirect to <host>:8102:

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> GET /sap/bc/idoc_xml?sap-client=222 HTTP/1.1

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> User-Agent: Mozilla/4.0 [en] (WinNT; I)

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Accept: image/gif, */*

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Host: <host>:8002

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Authorization:IMERCATOCPIC: ****

2017-10-23 16:39:54 CEST [ISC.0038.0002D] --> Content-Type: text/xml; charset=utf-8

2017-10-23 16:39:54 CEST [ISC.0040.0001D] HTTP/1.1 409

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- set-cookie: sap-usercontext=sap-client=222; path=/

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- set-cookie: MYSAPSSO2=AjQxMDMBABhJAE0ARQBSAEMAQQBUAE8AQwBQAEkAQwACAAYyADIAMgADABBFAFQAMQAgACAAIAAgACAABAAYMgAwADEANwAxADAAMgAzADEANAAzADkABQAEAAAACAYAAlgACQACRAD%2fAPYwgfMGCSqGSIb3DQEHAqCB5TCB4gIBATELMAkGBSsOAwIaBQAwCwYJKoZIhvcNAQcBMYHCMIG%2fAgEBMBMwDjEMMAoGA1UEAxMDRVQxAgEAMAkGBSsOAwIaBQCgXTAYBgkqhkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNzEwMjMxNDM5NTRaMCMGCSqGSIb3DQEJBDEWBBScs3VXM4JAY3%21zMwfTa%21MlAQdvfjAJBgcqhkjOOAQDBDAwLgIVALUiNbfyt3KFx%2153d5h4FJ0JY38JAhUAw6Sj5h3%2fb90PXbPW9wh9kvICiRY%3d; path=/

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- set-cookie: SAP_SESSIONID_ET1_222=W2R1HsirLZeDzchK7SpQngi4hf-4ABHnpRlcuQHb9ZA%3d; path=/

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- content-type: text/html; charset=utf-8

2017-10-23 16:39:54 CEST [ISC.0038.0002D] <-- content-length: 129

What can you do so that the POST is also executed as POST an the redirected system?