CPI error "java.lang.StringIndexOutOfBoundsException" in Groovy Script

[StefanK]

Hello experts,

I have encountered the following error in a Groovy script. The error appears in several parts of the code:

com.sap.it.rt.adapter.http.api.exception.HttpResponseException: An internal server error occurred: java.lang.StringIndexOutOfBoundsException: String index out of range: 2 at line 82 in script1.groovy.
Code:
String test_type = TERST_PNR.substring(1, 2);

com.sap.it.rt.adapter.http.api.exception.HttpResponseException: An internal server error occurred: java.lang.StringIndexOutOfBoundsException: String index out of range: -2 at line 171 in script1.groovy.
Code:
if (xmlstr.substring(getXMLTag_startindex2 - 2, getXMLTag_startindex2 - 1).equals("/"))

com.sap.it.rt.adapter.http.api.exception.HttpResponseException: An internal server error occurred: java.lang.StringIndexOutOfBoundsException: String index out of range: -145 at line 195 in script1.groovy.
Code:
String tagtext = xmlstr.substring(getXMLTag_startindex2, getXMLTag_endindex1);

com.sap.it.rt.adapter.http.api.exception.HttpResponseException: An internal server error occurred: java.lang.StringIndexOutOfBoundsException: String index out of range: 3 at line 144 in script1.groovy.
Code:
"  <p1:SYSID>" + SNDPRN.substring(0, 3) + "</p1:SYSID>\r\n"

In each code section, the "substring" method is used. The error does not always occur. Three percent of all messages encounter this error.

Strangely enough, when I restart the messages in the ERP system, they are transmitted without errors. I have no chance to trace the message and reproduce the error

Has anyone experiences with this error? How can it be resolved? Is there a way to log the payload without enabling the trace?

Thank you in advance for your support!

Best regards,

Stefan

[Bibhu · Accepted solution]

Always check the input string before performing the substring operation 

Can you try logging the payload if there is an error? 

import com.sap.gateway.ip.core.customdev.util.Message

def Message processData(Message message) {
    def payload = message.getBody(java.lang.String) as String
    def messageLog = messageLogFactory.getMessageLog(message)
    
    try {
        // code that could potentially throw an exception 
        String test_type = payload.substring(1, 2) 
        
    } catch (Exception e) {  
        //Log the payload and the exception details
        if (messageLog != null) {
            //Log the payload as an attachment in the message logs
            messageLog.addAttachmentAsString("Payload with Error", payload, "text/plain")
            
            //Log the exception message and type in the message properties
            messageLog.setStringProperty("ExceptionType", e.getClass().getName())
            messageLog.setStringProperty("ExceptionMessage", e.message)
        }

        // Re-throw the exception or handle it accordingly
        throw new RuntimeException("Error during processing: " + e.getClass().getName() + " - " + e.message)
    }

    return message
}