Parsing JSON Arrays with PeopleCode

PeopleCode includes built-in support for parsing JSON through a native object called the JsonParser. Let's review a couple of JSON strings and then see how the JsonParser interprets them. First, let's review a JsonObject:

{
  "course": "PT1",
  "description": "PeopleTools",
  "courseType": "T",
  "duration": 4
}

Assuming that the JSON text is in the string variable &jsonStr, then we might parse it with code similar to:

Local JsonParser &p = CreateJsonParser();

If (&p.Parse(&jsonStr)) Then
  REM ** Woo Hoo! It parsed!;
End-If;

Parsing means the JsonParser created an in-memory structure. To leverage the JSON, we need to access that in-memory structure. The JsonParser includes one documented method to access the JSON Structure: GetRootObject(). The GetRootObject method returns a JsonObject. According to the documentation, the following PeopleCode should give us the value of the description attribute from the JSON above:

Local JsonObject &course = &p.GetRootObject();
Local string &descr; = &course.GetString("description");

What about a JSON Array? Here is my concern: There is no GetRootArray method. What if the "root object" is not an "object," but an Array? Here is what a valid JSON Array might look like:

[{
  "course": "PT1",
  "description": "PeopleTools",
  "courseType": "T",
  "duration": 4
}, {
  "course": "PC",
  "description": "PeopleCode",
  "courseType": "T",
  "duration": 5
}]

We would parse it using the same code as above. But how would you access the Array? Since the Parser has a GetRootObject method, let's invoke it, and then ToString the root object to see its JSON output. Here is the PeopleCode:

MessageBox(0, "", 0, 0, "%1", &p.GetRootObject().ToString());

... and here is the JSON:

{[
    {
        "course": "PT1",
        "description": "PeopleTools",
        "courseType": "T",
        "duration": 4
    },
    {
        "course": "PC",
        "description": "PeopleCode",
        "courseType": "T",
        "duration": 5
    }
]}

Do you notice anything unusual about that JSON? Notice the extra curly braces ({}). The "root" object is a JSON object. But here is where it gets interesting. The printed JSON is not valid. An object must have an attribute. The array should be assigned to an attribute. Now, does this matter? I think Oracle is allowed to internally represent JSON any way they desire. You might say that what we did was unexpected. We asked PeopleSoft to print an internal representation, not a true, expected JSON Object. But my question is the same: How do you access the Array that is now inside the root object? Here is the answer:

&p.GetRootObject().GetJsonArray("");

The GetJsonArray method expects an attribute name. We don't have one. So we don't give it one. Just use a zero-length string.

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