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XPRIM_JsonObject and XPRIM_JsonArray is an in-memory representation of JSON objects and JSON arrays. They store their child elements in a tree-like structure in memory, to support random access of elements by member name and array index. XPRIM_JsonObject and XPRIM_JsonArray have a common superclass, XPRIM_JsonElement.
As XPRIM_JsonObject/XPRIM_JsonArray are both readable and modifiable (with random access support), they are useful when you need to create an abstract, in-memory, representation of your JSON data, that you need to pass around, to another routine or any third-party library routines.
Note however that if you just need to construct a JSON string (that is, a string representation of a JSON data), you should use XPRIM_JsonWriter instead as XPRIM_JsonWriter is specifically designed to construct a JSON string, so it does that very efficiently, with a minimum memory footprint. Similarly, if you just need to parse a JSON string and read its values, you'd be better off using XPRIM_RandomAccessJsonReader or XPRIM_JsonReader. XPRIM_JsonWriter and XPRIM_JsonReader will be discussed in the next section.
Here is how you create an XPRIM_JsonObject and an XPRIM_JsonArray:
Define_Com Class(#XPRIM_JsonObject) Name(#RootObject)Define_Com Class(#XPRIM_JsonArray) Name(#JsonArray)
You can then populate your JSON object or JSON array with values.
JSON data has 6 value types:
- Null
- String
- Number
- Boolean
- Object
- Array
Both XPRIM_JsonObject and XPRIM_JsonArray have the following methods that each correspond to the type of value it inserts to the object or array:
- InsertNull
- InsertString
- InsertNumber
- InsertBoolean
- InsertElement (insert any kind of JSON element, including JSON array and object)
Note however that the XPRIM_JsonObject's Insert methods would have a Key parameter that specifies the property name of the value to be inserted, whereas the XPRIM_JsonArray's Insert methods wouldn't have a Key parameter as it would just append the value to the end of the array.
Examples:
* Insert a string "John" as the "name" property of a JSON object#RootObject.InsertString Key('name') String('John')
* Insert a number 9 into a JSON array#JsonArray.InsertNumber Number(9)
* Insert a NULL value as the "allergies" property of a JSON object#RootObject.InsertNull Key('allergies')
The following example show how to create an object/array as a property of another object:
* Define an XPRIM_JsonObject referenceDefine_Com Class(#XPRIM_JsonObject) Name(#ChildObject)
* Insert the street & suburb of the address into #ChildObject#ChildObject.InsertString Key('street') String('122 Arthur St')#ChildObject.InsertString Key('suburb') String('North Sydney')
* Insert #ChildObject into #RootObject as a member with name "address"#RootObject.InsertElement Key('address') Element(#ChildObject)
If you want to convert your XPRIM_JsonObject (or XPRIM_JsonArray) into a string (for example for debugging purpose), call the SerializeAsString method.
Define_Com Class(#PRIM_DC.UnicodeString) Name(#MyJsonString)
* Convert JSON to a string#MyJsonString := #RootObject.SerializeAsString
You can also serialize your JSON object (or array) into a file, using the SerializeToFile method.
#RootObject.SerializeToFile Path('/home/TestJson.txt')
You can also parse a JSON string and construct an XPRIM_JsonObject or XPRIM_JsonArray from the JSON string, using the ParseString and ParseFile methods.
* Define an ErrorInfo object to hold the error detailsDefine_Com Class(#XPRIM_ErrorInfo) Name(#ErrorInfo)
* Call the 'Parse' method#RootObject.ParseString String(#JsonString) ErrorInfo(#ErrorInfo)
* Get the error message if parsing failedIf (*Not #ErrorInfo.OK) #ErrorMessage := #ErrorInfo.ErrorMessageEndIf
You can access the values of an object or an array using one of the Get… accessor methods:
- GetString
- GetBoolean
- GetNumber
- GetObject
- GetArray
...
For example, if you have a JSON string like this, stored in a variable called '#String': \
{
...
...
"name":
...
...
{
...
...
"given":
...
"John",
...
...
"surname":
...
"Smith"
...
...
},
...
...
"age":
...
45,
...
...
"contactNo":
...
...
[
...
...
{
...
area:
...
"02",
...
no:
...
"9378
...
2867",
...
type:
...
"landline"
...
},
...
...
{
...
no:
...
"0468
...
732
...
371",
...
type:
...
"mobile"
...
}
...
...
]
...
}
To parse this JSON string and read its values:
Define_Com
...
Class(#XPRIM_JsonObject)
...
Name(#RootObject)
...
Define_Com
...
Class(#XPRIM_ErrorInfo)
...
Name(#ErrorInfo)
* Parse JSON string#RootObject.ParseString String(#String) ErrorInfo(#ErrorInfo)
* First check
...
that the JSON string was parsed OKIf (#ErrorInfo.OK) * Get the values #GivenName := #RootItem.GetObject('name').GetString('given') #Surname := #RootItem.GetObject('name').GetString('surname') #Age := #RootItem.GetNumber('age')Endif
You can use the ItemCount property to tell how many item an array (or object) contains.
Define_Com Class(#XPRIM_JsonArray) Name(#ContactNumbers)
* Get the contactNo value (which is an array), ...
* ... and assign to #ContactNumbers#ContactNumbers.Refer To(#RootItem.GetArray('contactNo')
* Get the array length using the 'ItemCount' property#ContactCount := #ContactNumbers.ItemCount
To iterate through elements in a JSON array, you can use the FOR-EACH-IN construct:
* Use the contactNo array from the previous exampleFOR EACH(#Number) IN(#ContactNumbers) #COM_SELF.ProcessContactNumber Number(#Number)ENDFOR
You can check the type of a JSON element (XPRIM_JsonElement) by reading its Type property, which will return one of the following values:
- NULL
- STRING
- NUMBER
- BOOLEAN
- OBJECT
- ARRAY
If you just want to check if a JSON element is of a certain type, you can use one of the Is… method:
- IsNull
- IsString
- IsNumber
- IsBoolean
- IsObject
- IsArray