How Use Advanced Mappings (Interpolations)
1. What you will learn
In this tutorial you will learn how to bring mappings to the next level by using PAKs Interpolation to manipulate variables from the datastore.
3. Commands to Use
Figure 1. The Write Value command
Command that take an input value and simply writes it to the datastore. |
Figure 2. The Simple Ok command
Command which simply shows an informational text together with an ok button. |
4. Advanced Mappings
Interpolations are used to extend the functionality of constant mappings. An interpolation can be integrated in any string mapping using the syntax ${interpol} where interpol is of one of the types described below.
| For a complete rundown of the syntax for interpolations, please refer to the syntax reference. |
4.1. Json Interpolation
In PAK, all data that passes the datastore is transformed to the JSON format. This allows us to perform transformations on stored values via the JSON path syntax.
| In the figures 4, 6 and 8 the third marking points towards the fast interpolation tool. When clicking on it you can interpolate towards a datastore key. However, this tool can only create interpolations for datastore keys. Therefore if you want to get a specific field of a datastore item, you’ll need to adjust the interpolation manually to point to that field! |
4.1.1. The Workflow
In order to demonstrate JSON path interpolation we will need a JSON in the datastore that we can perform actions on. So let’s set up a very simple workflow that merely writes a value into the datastore and prints the result.
{
"name" : "Max",
"age" : 33,
"hobbies" : [
{
"name" : "Soccer",
"id" : 0
},
{
"name" : "Coding",
"id" : 1
},
{
"name" : "Automating Workflows",
"id" : 2
}
]
}To use that JSON in our command we create a constant mapping for readValue as described in the previous tutorial.
4.1.2. Json Path Mapping
As you can see, our JSON model represents a person that has a name, age, and a list of hobbies attached. However, we might only be interested in the persons name. As the JSON will be written by the Write Value command, we can reference it with writtenValue. So in order to extract the name from the JSON data we use JSON pathing and create a constant mapping on messageText containing ${writtenValue.name} (Fig 4).
Figure 4. Json Path Mapping
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Figure 5. Json Path Mapping Result
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After running the workflow in the PAK Workflow Executor (Download) we get the desired result as shown in Fig 5.
Of course, we have the freedom to interpolate how we desire. For example, we could also extract the age into the same string by mapping messageText to Name: ${writtenValue.name} | Age: ${writtenValue.age} (Fig 6) like shown below.
Figure 6. Json Path Mapping 2
|
Figure 7. Json Path Mapping 2 Result
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4.1.3. Json Array Mapping
The list of hobbies is not really looking appealing due to each element being a JSON itself. Using JSON array mapping we can extract only the name of the hobbies in our interpolation. This can be done by simply mapping messageText to ${writtenValue.hobbies.name} (Fig 8).
Figure 8. Json Array Mapping
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Figure 9. Json Array Mapping Result
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To select a specific item from the list we can specify an index like writtenValue.hobbies[1] which will result in:
| Make sure that the index you are using is withing the bounds of the JSON array |
Alternatively we can specify to extract either the first, or the last value like writtenValue.hobbies[:], respectively writtenValue.hobbies[-:].
4.2. Environmental Interpolation
While you can fetch values from PAKs datastore, sometimes the need arises to acquire values that were not necessarily written, for example the location of the users home directory.
As environmental mappings are not dependent on the datastore, we can simply take the workflow from Fig 3 and omit the Write Value command leaving us with the following workflow.
| In figures 12 and 13 the third marker points towards the fast interpolation tool. As the fast interpolation tool can only create interpolations of datastore keys, you’ll need to create the environment interpolations manually! |
Not only can we acquire values from the Java runtime, but also our operating systems environment variables. For example, on a Windows system we can check for the user home using the UserProfile environment variable analogous. (Fig 13)
