SOA Suite 12c Stumbling on parsing Ampersands

Yesterday I ran into a problem parsing xml in BPEL. A bit of context: I get messages from a JMS queue, that I read 'Opaque'. Because I want to be able to dispatch the messages to different processes based on a generic WSDL, but with a different payload.

So after the Base64 Decode, for which I have a service, I need to parse the content to XML. Now, I used to use the oraext:parseEscapedXML() function for it. This function is known to have bugs, but I traced that down to BPEL 10g. And I'm on 12.2.1.3 now.

Still I got exceptions as:

<bpelFault><faultType>0</faultType><subLanguageExecutionFault xmlns="http://docs.oasis-open.org/wsbpel/2.0/process/executable"><part name="summary"><summary>An error occurs while processing the XPath expression; the expression is oraext:parseEscapedXML($Invoke_Base64EncodeDecodeService_decode_OutputVariable.part1/ns5:document)</summary></part><part name="code"><code>XPath expression failed to execute</code></part><part name="detail"><detail>XPath expression failed to execute.
An error occurs while processing the XPath expression; the expression is oraext:parseEscapedXML($Invoke_Base64EncodeDecodeService_decode_OutputVariable.part1/ns5:document)
The XPath expression failed to execute; the reason was: oracle.fabric.common.xml.xpath.XPathFunctionException: Expected ';'.
Check the detailed root cause described in the exception message text and verify that the XPath query is correct.
</detail></part></subLanguageExecutionFault></bpelFault>

Or:

<bpelFault><faultType>0</faultType><subLanguageExecutionFault xmlns="http://docs.oasis-open.org/wsbpel/2.0/process/executable"><part name="summary"><summary>An error occurs while processing the XPath expression; the expression is oraext:parseEscapedXML($Invoke_Base64EncodeDecodeService_decode_OutputVariable.part1/ns5:document)</summary></part><part name="code"><code>XPath expression failed to execute</code></part><part name="detail"><detail>XPath expression failed to execute.
An error occurs while processing the XPath expression; the expression is oraext:parseEscapedXML($Invoke_Base64EncodeDecodeService_decode_OutputVariable.part1/ns5:document)
The XPath expression failed to execute; the reason was: oracle.fabric.common.xml.xpath.XPathFunctionException: Expected name instead of  .
Check the detailed root cause described in the exception message text and verify that the XPath query is correct.
</detail></part></subLanguageExecutionFault></bpelFault>

It turns out that it was due to ampersands (&) in the message. The function oraext:parseEscapedXML() is known to stumble on that.

A work around is suggested in a forum on Integration Cloud Service (ICS).  It suggests to use oraext:get-content-as-string() first. And feed the contents to oraext:parseEscapedXML(). It turns out that that helps, although I had to fiddle around with xpath expressions, to get the correct child element, since I also got the parent element surrounding the part I actually wanted to parse.

But then I found this blog, suggesting that it was replaced by oraext:parseXML() in 12c (I found that it is actually introduced in 11g).

Strange that I didn't find this earlier. Digging deeper down memory-lane, I think I must have seen the function before.  However, it shows I'm still learning all the time.