Structures shall be encoded as JSON objects.
Note that JSON objects are unordered sets of name-value pairs. The order specified by the DataTypeDefinition is not preserved when a Structure is serialized in JSON.
Fields which are NULL or have a default value shall be encoded using the rules shown in Table 44.
Table 44 – JSON Encoding Rules for Structures
Field Value |
Compact |
Verbose |
NULL |
Omitted |
JSON null |
Default Value |
Omitted |
Default Value |
For example, instances of the structures:
struct Type2
{
Int32 A;
Int32 B;
Char* C;
};
struct Type1
{
Int32 X;
Int32 NoOfY;
Type2* Y;
Int32 Z;
};
The CompactEncoding is represented in JSON as:
{
"X":1234,
"Y":[ { "A":1, "B":2, "C":"Hello" }, { "A":3, "B":4 } ],
"Z":5678
}
Where “C” is omitted from the second Type2 instance because it has a NULL value.
The VerboseEncoding is represented in JSON as:
{
"X":1234,
"Y":[ { "A":1, "B":2, "C":"Hello" }, { "A":3, "B":4, "C":null } ],
"Z":5678
}
Where “C” in the second Type2 instance has a JSON null value.
Code generators should ensure that the special field names (UaType, UaTypeId and EncodingMask) are not permitted in Structures.