Sunday, December 01, 2019

OIC Integration: defining and using constants

Oracle Integration Cloud does not have native support for constants, but it is easy to set this up. This post discusses how.

For integrations there are two ways to define constants in the Oracle Integration Cloud:
  • Lookups
  • Variables

Lookups are initially meant to support mapping of values from one domain to another. For example, one domain has country code using two letters ("NL") whereas another domain uses three letters ("NLD"). The lookup can then be used to "translate" the value from one to the other ("NL" <-> "NLD"). The same feature can also be used to support configurable constants by providing a list of name-value pairs. For example, in the following SMColor lookup two different name-value pairs have been stored, "YELLOW" with value "yellow", and "BLUE" with value "blue":

In an integration you can use this lookup to get the value by name using an XPath lookup function. As I will show hereafter, there are two different XPath expressions, each being used in a different context.

Variables are set in an Integration using the Assign activity. You can define a variable with a specific name and a value. You can also use a combination of the two. In the following example you see the variable "red" being defined with value "red" and the variable "blue" is initiated using an XPath expression that on its turn gets the value from the lookup name-value pair with name "BLUE":

Now let's have a look at how this can be used in a Mapper activity. In the following picture you see three different elements being mapped from respectively the lookup, the variable and the combination of both:

The response of my service looks as follows:

  "statusFromLookup": "yellow",
  "statusFromVariable": "red",
  "statusFromBoth": "blue"

Note that the XPath expression used to initiate the variable, is different from the Mapper activity. The difference of expression is whether the lookup function is used from XSLT as the Mapper activity does, or not.

When used in a Mapper activity use an expression like the following:

dvm:lookupValue ("tenant/resources/dvms/SMColors", "Name", "YELLOW", "Value", "not found") 

Otherwise use an expression like this:

dvm:lookupValue('oramds:/apps/ICS/DVM/SMColors.dvm','Name','BLUE','Value','not found')

Now when to use what? Some pointers:
  • To change a variable in an integration, you will have to modify the integration and reactivate it. You can do that as a new, minor version to prevent downtime. Not a task for any type of OIC user.
  • The threshold for someone to change a Lookup is lower. More suitable for values that need to be changed run-time (you don't have to re-activate the using integrations) for example by an Application Administrator.
  • It is easy to make a mistake in the XPath expression. So when you have to use it in an integration multiple times, consider using the combination as mapping a variable is simple.
  • Execution of an XPath expression has a small, but still a performance penalty.

For Structured and Dynamic Process there also is more than one way, which I will also discuss in some next blog topic. None of the above solutions support "versioned" parameters. I will discuss how to do that as well.

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